COAL GAS.(‡ Coal Gas Distillery.)SECTION OF RETORT.(‡ Receiver Tube.)FIG.2.(‡ Retort Furnace.)FIG.1.(‡ Condenser.)FIG.3.Gas, for lighting, is made from coal, by subjecting it to heat in iron tubes and collecting and purifying the gas which is produced; the following is a summary of the process:—The vessels in which the coal is put are called “retorts,” they are six or seven feet long, one-and-a-half broad, and one high, generally fitted up six to a furnace, in such a way that the flame may entirely surround them (seefig. 1); from each retort an iron tube passes, and these all dip into a large horizontal tube, reaching nearly to its bottom (fig. 2), this is the receiver for all the gas from the retorts; it is connected with a pit for tar and ammonical liquor, which copiously condenses from the hot newly-formed gas. The object of causing the tubes to dip nearly to the bottom of the receiver is, that the fluid in it may close the end of each tube, and so prevent the gas returning when any of the retorts are opened for a fresh supply of coal; from the receiver, the gas passes by tubes bent up and down inside of a great cistern of water (fig. 3) kept cold by a constant change of its contents; this is the condenser, it causes the separation of all the tar and ammonia that remain; but the gas is still contaminated with sulphur, and this is got rid of by causing it to pass into a broad iron cylinder perforated with holes and dipping into a reservoir of lime and water mixed together and stirred about with a machine contrived for the purpose; the gas enters this lime mixture in hundreds of bubbles through the holes, and the sulphur the gas contains is attracted by the lime with which it unites. The gas now rises to the top of this reservoir, which is, of course, air tight, and from thence passes for use to the gasometer; this is the store-house where the gas is kept to supply the service pipesb,c, under the streets.(‡ Reservoir.)FIG.4.(‡ Gasometer.)FIG.5.The gasometer is made of plates of iron rivetted together. The lower part of this cylinder (seefigs. 4and5) is received into a circular deep channel cut in the ground (b b,fig. 5) and filled with water, so that the gasometerd, which is suspended and balanced by means of the chains and weightse e, may be raised or depressed at pleasure. When the gasometer is quite down, the inside of its top,a, rests on the ground; when the gas enters, it raises it up till the lower edge is but a few inches below the water, and is prevented from rising higher by frames which support it; when some of the weights,d d, are removed, the huge cylinder,a, slowly sinks down and forces the gas through the tubes,c c, to be burnt by thousands of consumers. About four cubic feet of gas is produced from every pound of coal used; the gas is lighter than air in the proportion of 650 to 1000, and it is owing to this lightness that balloons ascend when filled with it, not from any peculiar power it has of ascending, but because the air, being heavier, presses downwards and forces it up. When gas is mixed with air it becomes very explosive, and when any escape is suspected in a room, the windows of the room should be openedat the top, and the door also opened, before any light is introduced; a few minutes will then suffice to ensure safety.One ton of good coal produces—1Chaldron of Coke,weighing1494lbs.12Gallons of Tar”135”12Gallons Ammoniacal liquor100”9500Cubic feet of Gas,weighing291”Loss (chiefly water)”220”2240lbs.A cubic foot of gas weighs 514 and a-half grains.
(‡ Coal Gas Distillery.)
SECTION OF RETORT.(‡ Receiver Tube.)FIG.2.
SECTION OF RETORT.
SECTION OF RETORT.
(‡ Receiver Tube.)FIG.2.
FIG.2.
(‡ Retort Furnace.)FIG.1.(‡ Condenser.)FIG.3.
(‡ Retort Furnace.)FIG.1.
FIG.1.
(‡ Condenser.)FIG.3.
FIG.3.
Gas, for lighting, is made from coal, by subjecting it to heat in iron tubes and collecting and purifying the gas which is produced; the following is a summary of the process:—The vessels in which the coal is put are called “retorts,” they are six or seven feet long, one-and-a-half broad, and one high, generally fitted up six to a furnace, in such a way that the flame may entirely surround them (seefig. 1); from each retort an iron tube passes, and these all dip into a large horizontal tube, reaching nearly to its bottom (fig. 2), this is the receiver for all the gas from the retorts; it is connected with a pit for tar and ammonical liquor, which copiously condenses from the hot newly-formed gas. The object of causing the tubes to dip nearly to the bottom of the receiver is, that the fluid in it may close the end of each tube, and so prevent the gas returning when any of the retorts are opened for a fresh supply of coal; from the receiver, the gas passes by tubes bent up and down inside of a great cistern of water (fig. 3) kept cold by a constant change of its contents; this is the condenser, it causes the separation of all the tar and ammonia that remain; but the gas is still contaminated with sulphur, and this is got rid of by causing it to pass into a broad iron cylinder perforated with holes and dipping into a reservoir of lime and water mixed together and stirred about with a machine contrived for the purpose; the gas enters this lime mixture in hundreds of bubbles through the holes, and the sulphur the gas contains is attracted by the lime with which it unites. The gas now rises to the top of this reservoir, which is, of course, air tight, and from thence passes for use to the gasometer; this is the store-house where the gas is kept to supply the service pipesb,c, under the streets.
(‡ Reservoir.)FIG.4.
FIG.4.
(‡ Gasometer.)FIG.5.
FIG.5.
The gasometer is made of plates of iron rivetted together. The lower part of this cylinder (seefigs. 4and5) is received into a circular deep channel cut in the ground (b b,fig. 5) and filled with water, so that the gasometerd, which is suspended and balanced by means of the chains and weightse e, may be raised or depressed at pleasure. When the gasometer is quite down, the inside of its top,a, rests on the ground; when the gas enters, it raises it up till the lower edge is but a few inches below the water, and is prevented from rising higher by frames which support it; when some of the weights,d d, are removed, the huge cylinder,a, slowly sinks down and forces the gas through the tubes,c c, to be burnt by thousands of consumers. About four cubic feet of gas is produced from every pound of coal used; the gas is lighter than air in the proportion of 650 to 1000, and it is owing to this lightness that balloons ascend when filled with it, not from any peculiar power it has of ascending, but because the air, being heavier, presses downwards and forces it up. When gas is mixed with air it becomes very explosive, and when any escape is suspected in a room, the windows of the room should be openedat the top, and the door also opened, before any light is introduced; a few minutes will then suffice to ensure safety.
One ton of good coal produces—
1Chaldron of Coke,weighing1494lbs.12Gallons of Tar”135”12Gallons Ammoniacal liquor100”9500Cubic feet of Gas,weighing291”Loss (chiefly water)”220”2240lbs.A cubic foot of gas weighs 514 and a-half grains.
TAR.(‡ Tar Factory.)Tar is one of the results left in the distillation both of wood and coal; in places where wood is plentiful and tar in request, it is produced by burning the wood for that purpose; and in some of the pits in which charcoal is produced, an arrangement is made to collect the tar also. Coal-tar and wood-tar are different in some respects, and are both distilled to procure the napthas which bear the respective names. From wood-tar, creasöte is also extracted, and it is this substance which gives the peculiar tarry flavor to provisions cured or preserved by being smoked over wood fires, such as ham, bacon, or herrings. Tar is used as a sort of paint for covering wood-work and cordage, when much exposed to wet, which it resists better than anything else at the same price; but the tar chiefly used for these purposes, is that produced by burning fir or deal wood and condensing the tar in a pit below the stack of wood, it is called Stockholm tar, as it comes chiefly from that place.
(‡ Tar Factory.)
Tar is one of the results left in the distillation both of wood and coal; in places where wood is plentiful and tar in request, it is produced by burning the wood for that purpose; and in some of the pits in which charcoal is produced, an arrangement is made to collect the tar also. Coal-tar and wood-tar are different in some respects, and are both distilled to procure the napthas which bear the respective names. From wood-tar, creasöte is also extracted, and it is this substance which gives the peculiar tarry flavor to provisions cured or preserved by being smoked over wood fires, such as ham, bacon, or herrings. Tar is used as a sort of paint for covering wood-work and cordage, when much exposed to wet, which it resists better than anything else at the same price; but the tar chiefly used for these purposes, is that produced by burning fir or deal wood and condensing the tar in a pit below the stack of wood, it is called Stockholm tar, as it comes chiefly from that place.
ACETIC ACID, OR WOOD VINEGAR.Acetic acid forms a considerable article of commerce. It is not only used in medicine and the culinary art, but is extensively employed in forming acetate of iron for dyeing and calico printing. To prepare it, large iron cylinders, about eight feet long and three in diameter, are embedded in brickwork in a row, and in such a manner that furnaces placed below may heat them red-hot; these cylinders have a tube leading from each into a main tube, where the liquid products from each cylinder are received for condensation; the other end of the cylinder has a plate of iron fitting closely to it. The cylinders are filled with logs of wood, either oak, beech, birch, or ash, the door is closely fastened and the joints smeared with clay; the fires are now lighted and kept up all day, till the cylinders are red-hot; at night they are allowed to cool. About seven or eight hundred weight of wood is put into each cylinder. In the morning, the charcoal, into which the wood is now converted, is withdrawn, and a fresh charge supplied; from this charge of wood about thirty or forty gallons of liquid is condensed in the main tube from each cylinder, the remainder being charcoal and gases which pass off; the liquid is acid, brown, and very offensive, and contains acetic acid, tar, and several other ingredients, among which may be named creasote; it is from this source all the creasote, so famous for the cure of toothache, is obtained. The next process is to purify this liquid; it is first distilled, and this separates much tar, it is then mixed with lime, evaporated to dryness, and heated to expel the remaining tar and other impurities; it is next mixed with sulphate of soda and water and the whole stirred together, the soda, now in unison with the acetic acid, is washed out from the lime and strained quite clear; it is afterwards evaporated till it crystallizes, and vitriol (sulphuric acid) then added; finally, the acetic acid is distilled over, and the acid left in unison with the soda, forming sulphate of soda, to be used in a similar process for the next batch of acid; the acetic acid is now quite colorless, transparent, and very sour, possessing a fragrant and agreeable smell. This acid is not pure acetic acid, but contains a considerable quantity of water. The acetic acid of commerce, mixed with seven times its bulk of water, forms an acid of about the strength of malt vinegar, perfectly wholesome, and, to many, more agreeable as a condiment.Pure acetic acid may be made by mixing dry acetate of potash with oil of vitriol in a retort, and distilling the acetic acid into a very cold receiver; this, when flavored with various volatile oils, forms the aromatic vinegar sold by druggists. It is a very strong acid, and if applied to the skin will quickly blister it.
Acetic acid forms a considerable article of commerce. It is not only used in medicine and the culinary art, but is extensively employed in forming acetate of iron for dyeing and calico printing. To prepare it, large iron cylinders, about eight feet long and three in diameter, are embedded in brickwork in a row, and in such a manner that furnaces placed below may heat them red-hot; these cylinders have a tube leading from each into a main tube, where the liquid products from each cylinder are received for condensation; the other end of the cylinder has a plate of iron fitting closely to it. The cylinders are filled with logs of wood, either oak, beech, birch, or ash, the door is closely fastened and the joints smeared with clay; the fires are now lighted and kept up all day, till the cylinders are red-hot; at night they are allowed to cool. About seven or eight hundred weight of wood is put into each cylinder. In the morning, the charcoal, into which the wood is now converted, is withdrawn, and a fresh charge supplied; from this charge of wood about thirty or forty gallons of liquid is condensed in the main tube from each cylinder, the remainder being charcoal and gases which pass off; the liquid is acid, brown, and very offensive, and contains acetic acid, tar, and several other ingredients, among which may be named creasote; it is from this source all the creasote, so famous for the cure of toothache, is obtained. The next process is to purify this liquid; it is first distilled, and this separates much tar, it is then mixed with lime, evaporated to dryness, and heated to expel the remaining tar and other impurities; it is next mixed with sulphate of soda and water and the whole stirred together, the soda, now in unison with the acetic acid, is washed out from the lime and strained quite clear; it is afterwards evaporated till it crystallizes, and vitriol (sulphuric acid) then added; finally, the acetic acid is distilled over, and the acid left in unison with the soda, forming sulphate of soda, to be used in a similar process for the next batch of acid; the acetic acid is now quite colorless, transparent, and very sour, possessing a fragrant and agreeable smell. This acid is not pure acetic acid, but contains a considerable quantity of water. The acetic acid of commerce, mixed with seven times its bulk of water, forms an acid of about the strength of malt vinegar, perfectly wholesome, and, to many, more agreeable as a condiment.
Pure acetic acid may be made by mixing dry acetate of potash with oil of vitriol in a retort, and distilling the acetic acid into a very cold receiver; this, when flavored with various volatile oils, forms the aromatic vinegar sold by druggists. It is a very strong acid, and if applied to the skin will quickly blister it.
VARNISHES.Varnishes are solutions of various resinous substances that will dry with a bright surface on exposure to the air. They are used to protect different substances from the action of the atmosphere, and to give them an elegant bright surface; woods and painted work are the chief things varnished; metals are coated with a kind of varnish called “lacquer,” this is to prevent the bright surface of the metal from being dulled by the air or damp, and to give an artificial appearance to some metals; tin, for instance, if lacquered with yellow lacquer, acquires somewhat the appearance of brass. Mastic varnish is the varnish generally used for paper and pictures; it is made by dissolving gum mastic in oil of turpentine. Copal varnish is that most generally used for carriages and wood, it is made by adding boiled linseed oil to melted copal, and afterwards thinning it with oil of turpentine. A common varnish, fit for many purposes, may be made by adding common resin to oil of turpentine, and warming it till dissolved. Lacquers are made by dissolving shellac and various other gums in strong spirits of wine, and in some cases coloring it, either yellow, by means of gamboge, or red, by dragon’s blood (a kind of resin). French polish is nearly the same as lacquer, but the mode of applying it is different; the grain of the wood is first filled up by means of drying oil and chalk rubbed in, when this becomes thoroughly dry, a rubber of flannel is covered by a piece or two of clean old linen, and some of the polish put on it, just enough to moisten it, and then a little oil, this is slowly rubbed round and round, the varnish adhering to the wood, and the oil preventing the rubber sticking to it, and at the same time, polishing the surface of the varnish as it dries. This process requires a good deal of art to produce a perfect surface.Old work, before being varnished with any varnish that contains oil (as copal varnish), should be thoroughly freed from grease or greasy matter, or the varnish will never dry. Good varnish should dry in twenty-four hours so that dust will not adhere to it.
Varnishes are solutions of various resinous substances that will dry with a bright surface on exposure to the air. They are used to protect different substances from the action of the atmosphere, and to give them an elegant bright surface; woods and painted work are the chief things varnished; metals are coated with a kind of varnish called “lacquer,” this is to prevent the bright surface of the metal from being dulled by the air or damp, and to give an artificial appearance to some metals; tin, for instance, if lacquered with yellow lacquer, acquires somewhat the appearance of brass. Mastic varnish is the varnish generally used for paper and pictures; it is made by dissolving gum mastic in oil of turpentine. Copal varnish is that most generally used for carriages and wood, it is made by adding boiled linseed oil to melted copal, and afterwards thinning it with oil of turpentine. A common varnish, fit for many purposes, may be made by adding common resin to oil of turpentine, and warming it till dissolved. Lacquers are made by dissolving shellac and various other gums in strong spirits of wine, and in some cases coloring it, either yellow, by means of gamboge, or red, by dragon’s blood (a kind of resin). French polish is nearly the same as lacquer, but the mode of applying it is different; the grain of the wood is first filled up by means of drying oil and chalk rubbed in, when this becomes thoroughly dry, a rubber of flannel is covered by a piece or two of clean old linen, and some of the polish put on it, just enough to moisten it, and then a little oil, this is slowly rubbed round and round, the varnish adhering to the wood, and the oil preventing the rubber sticking to it, and at the same time, polishing the surface of the varnish as it dries. This process requires a good deal of art to produce a perfect surface.Old work, before being varnished with any varnish that contains oil (as copal varnish), should be thoroughly freed from grease or greasy matter, or the varnish will never dry. Good varnish should dry in twenty-four hours so that dust will not adhere to it.
OILS.PRESSING LINSEED FOR OIL.Oils, whether animal or vegetable, have pretty much the same properties. The vegetable oils are got by crushing and pressing certain seeds, as linseed; the animal oils are obtained chiefly from the whale and seal tribe, or from fish, as the cod and sturgeon. They are viscid and of a pale yellow color, lighter than water, and therefore float upon it, and are very combustible. Oils are used for a multiplicity of purposes: for burning in lamps, for making paints and varnishes, preventing the friction of machinery, in making soap, and numerous other processes. Oils are generally divided into fixed and volatile oils; as an example of the first, linseed oil may be selected; of the last, oil of lavender.Some of the fixed oils are called drying oils, and it is this kind that are used for varnish making; as linseed oil possesses the properties of this class very perfectly, it may serve as a description of all. Linseed oil has the power of drying when spread out in a thin layer, becoming of a resinous consistence like varnish, and upon this quality depends the drying powers of paint, for the other non-drying oils, as olive oil, may be exposed to the air for months without drying at all; the drying powers of linseed oil are greatly increased by boiling it with litharge (oxide of lead). This forms the drying or boiled oil used in painting, and is employed in making varnishes, printers’ ink, and for other purposes. Oiled silk is formed by brushing silk over with this oil and exposing it to the air till it is dry; this oiled silk is the same that is used for sponge-bags and bathing-caps. Of the non-drying oils, the chief are those used for burning in lamps, as sperm oil. Salad oil is expressed from the olive, and is called olive oil. Of the volatile oils, the most useful is oil of turpentine, commonly called spirit of turpentine; it is got by distilling common turpentine (the concrete juice of trees of the fir and pine tribe), it has a strong odour, is very inflammable, and is volatile, that is to say, if spread out, will evaporate, leaving nothing behind; this oil is capable of mixing with drying oils, and it not only increases their drying powers, but, by thinning them, makes them more applicable to many purposes. Oil of turpentine dissolves resin and many resinous substances, and forms useful varnishes with them. Mastic varnish is mastic dissolved in oil of turpentine; it is the varnish always used for varnishing pictures. Many of the volatile oils are used as perfumes, and the odour of plants and flowers depends upon the volatile oil which evaporates from them, as lavender, cloves, and others. Peppermint water, dill water, and cinnamon water are produced by distilling water mixed with the substances, and is simply water containing a small quantity of the volatile oil of these substances in solution; but eau-de-Cologne and lavender water, although called “waters,” are mixtures of volatile oils and spirit of wine, and contain no more water than is comprehended in the spirit used.
PRESSING LINSEED FOR OIL.
PRESSING LINSEED FOR OIL.
Oils, whether animal or vegetable, have pretty much the same properties. The vegetable oils are got by crushing and pressing certain seeds, as linseed; the animal oils are obtained chiefly from the whale and seal tribe, or from fish, as the cod and sturgeon. They are viscid and of a pale yellow color, lighter than water, and therefore float upon it, and are very combustible. Oils are used for a multiplicity of purposes: for burning in lamps, for making paints and varnishes, preventing the friction of machinery, in making soap, and numerous other processes. Oils are generally divided into fixed and volatile oils; as an example of the first, linseed oil may be selected; of the last, oil of lavender.
Some of the fixed oils are called drying oils, and it is this kind that are used for varnish making; as linseed oil possesses the properties of this class very perfectly, it may serve as a description of all. Linseed oil has the power of drying when spread out in a thin layer, becoming of a resinous consistence like varnish, and upon this quality depends the drying powers of paint, for the other non-drying oils, as olive oil, may be exposed to the air for months without drying at all; the drying powers of linseed oil are greatly increased by boiling it with litharge (oxide of lead). This forms the drying or boiled oil used in painting, and is employed in making varnishes, printers’ ink, and for other purposes. Oiled silk is formed by brushing silk over with this oil and exposing it to the air till it is dry; this oiled silk is the same that is used for sponge-bags and bathing-caps. Of the non-drying oils, the chief are those used for burning in lamps, as sperm oil. Salad oil is expressed from the olive, and is called olive oil. Of the volatile oils, the most useful is oil of turpentine, commonly called spirit of turpentine; it is got by distilling common turpentine (the concrete juice of trees of the fir and pine tribe), it has a strong odour, is very inflammable, and is volatile, that is to say, if spread out, will evaporate, leaving nothing behind; this oil is capable of mixing with drying oils, and it not only increases their drying powers, but, by thinning them, makes them more applicable to many purposes. Oil of turpentine dissolves resin and many resinous substances, and forms useful varnishes with them. Mastic varnish is mastic dissolved in oil of turpentine; it is the varnish always used for varnishing pictures. Many of the volatile oils are used as perfumes, and the odour of plants and flowers depends upon the volatile oil which evaporates from them, as lavender, cloves, and others. Peppermint water, dill water, and cinnamon water are produced by distilling water mixed with the substances, and is simply water containing a small quantity of the volatile oil of these substances in solution; but eau-de-Cologne and lavender water, although called “waters,” are mixtures of volatile oils and spirit of wine, and contain no more water than is comprehended in the spirit used.
INKS.Inks are fluids of various kinds suitable for writing with pens. The chief inks in use are black, blue, and red writing inks, and indelible or marking ink, intended for marking linen which has to be washed. Indian ink is not used as an ink, properly so called. All the black inks in use are composed of green vitriol (sulphate of iron), in union with some astringent vegetable matter, the best is the gall-nut, although, for cheapness, logwood and oak bark have each been used. An excellent black ink may be made by putting into a gallon stone bottle twelve ounces of bruised galls, six ounces of green vitriol, and six of common gum, and filling up the bottle with rain water, this should be kept three or four weeks before using, shaking the bottle from time to time. Blue ink has lately been much used, it is made by dissolving newly-formed Prussian blue in a solution of oxalic acid. To make it, dissolve some yellow prussiate of potash in water in one vessel, and some sulphate of iron in another, adding a few drops of nitric acid to the sulphate of iron; now mix the two liquids, and a magnificent blue color will appear in the form of a light sediment; this is to be put upon a paper filter, and well washed by pouring over it warm water and allowing it to run through; a warm solution of oxalic acid should now be mixed with it, and the Prussian blue will dissolve into a bright blue ink.Red ink is made by boiling chips or raspings of Brazil wood in vinegar, and adding a little alum and gum; it keeps well, and is of a good color. A red ink of more beautiful appearance, but not so durable, may be made by dissolving a few grains of carmine in two or three tea-spoonfuls of spirit of hartshorn.Marking ink is made by dissolving nitrate of silver in water, and then adding some solution of ammonia, a little gum water, and some Indian ink to color it. Printers’ ink is made by grinding drying oil with lamp-black.
Inks are fluids of various kinds suitable for writing with pens. The chief inks in use are black, blue, and red writing inks, and indelible or marking ink, intended for marking linen which has to be washed. Indian ink is not used as an ink, properly so called. All the black inks in use are composed of green vitriol (sulphate of iron), in union with some astringent vegetable matter, the best is the gall-nut, although, for cheapness, logwood and oak bark have each been used. An excellent black ink may be made by putting into a gallon stone bottle twelve ounces of bruised galls, six ounces of green vitriol, and six of common gum, and filling up the bottle with rain water, this should be kept three or four weeks before using, shaking the bottle from time to time. Blue ink has lately been much used, it is made by dissolving newly-formed Prussian blue in a solution of oxalic acid. To make it, dissolve some yellow prussiate of potash in water in one vessel, and some sulphate of iron in another, adding a few drops of nitric acid to the sulphate of iron; now mix the two liquids, and a magnificent blue color will appear in the form of a light sediment; this is to be put upon a paper filter, and well washed by pouring over it warm water and allowing it to run through; a warm solution of oxalic acid should now be mixed with it, and the Prussian blue will dissolve into a bright blue ink.
Red ink is made by boiling chips or raspings of Brazil wood in vinegar, and adding a little alum and gum; it keeps well, and is of a good color. A red ink of more beautiful appearance, but not so durable, may be made by dissolving a few grains of carmine in two or three tea-spoonfuls of spirit of hartshorn.
Marking ink is made by dissolving nitrate of silver in water, and then adding some solution of ammonia, a little gum water, and some Indian ink to color it. Printers’ ink is made by grinding drying oil with lamp-black.
CHARCOAL.(‡ Charcoal Ovens.)Charcoal is made by burning wood in such a manner that but little air shall be admitted during the operation, that is to say, only sufficient to keep up the combustion of the more easily destroyed parts of the wood, leaving a black residue called charcoal. The best charcoal is made when the wood is quite excluded from the air, as in making acetic acid, but where large quantities of charcoal are used for common fuel, as in France, of course this process is too expensive. The usual way is to pile up billets of wood and cover the whole with turf; when fired, the wood consumes gradually and the charcoal is left behind. Charcoal is light and porous, and of a shining black color; it weighs about one quarter as much as the wood used, and burns without flame or smoke, giving out a strong heat. When charcoal burns, it combines with part of the air, and is converted into a gas called carbonic acid, which, although invisible, is much heavier than air, and is a deadly poison; it is therefore necessary, where charcoal is burning, to always have some opening at thebottomof the room. Many fatal accidents have arisen from people sleeping in a small room with a pot of burning charcoal, and no outlet for the poisonous vapour but the chimney, up which it will not pass on account of its weight. Charcoal enters into the composition of gunpowder, and is used for several other purposes. It is an excellent sweetener of foul water, and a few pieces should always be kept in the top of the filter when the water has any bad odour, or in the cistern or butt, where a filter is not used; powdered charcoal has also the power of taking away the color of many liquids, as well as the bad smell; vinegar, if warmed with powdered charcoal, and then strained, will be almost colorless. Water butts are sometimes burnt or charred inside, that the water may be the better preserved in them.Chemically considered, charcoal consists of carbon with a certain amount of earthy matter (the ashes or earthy part of the wood from which it was made), but these ashes may be easily removed by maceration in an acid; the charcoal then remains unaltered in appearance and consists of carbon, but its structure is exceedingly porous.
(‡ Charcoal Ovens.)
Charcoal is made by burning wood in such a manner that but little air shall be admitted during the operation, that is to say, only sufficient to keep up the combustion of the more easily destroyed parts of the wood, leaving a black residue called charcoal. The best charcoal is made when the wood is quite excluded from the air, as in making acetic acid, but where large quantities of charcoal are used for common fuel, as in France, of course this process is too expensive. The usual way is to pile up billets of wood and cover the whole with turf; when fired, the wood consumes gradually and the charcoal is left behind. Charcoal is light and porous, and of a shining black color; it weighs about one quarter as much as the wood used, and burns without flame or smoke, giving out a strong heat. When charcoal burns, it combines with part of the air, and is converted into a gas called carbonic acid, which, although invisible, is much heavier than air, and is a deadly poison; it is therefore necessary, where charcoal is burning, to always have some opening at thebottomof the room. Many fatal accidents have arisen from people sleeping in a small room with a pot of burning charcoal, and no outlet for the poisonous vapour but the chimney, up which it will not pass on account of its weight. Charcoal enters into the composition of gunpowder, and is used for several other purposes. It is an excellent sweetener of foul water, and a few pieces should always be kept in the top of the filter when the water has any bad odour, or in the cistern or butt, where a filter is not used; powdered charcoal has also the power of taking away the color of many liquids, as well as the bad smell; vinegar, if warmed with powdered charcoal, and then strained, will be almost colorless. Water butts are sometimes burnt or charred inside, that the water may be the better preserved in them.
Chemically considered, charcoal consists of carbon with a certain amount of earthy matter (the ashes or earthy part of the wood from which it was made), but these ashes may be easily removed by maceration in an acid; the charcoal then remains unaltered in appearance and consists of carbon, but its structure is exceedingly porous.
CEMENTS.In various processes, cements of different descriptions are required for a variety of purposes. The common cement used in building, which is called mortar, is made of sand and quicklime mixed with water. Roman and Portland cements consist of certain kinds of clay burnt and ground. Plaster of Paris forms a useful cement, it is to be mixed with water to the consistence of cream, and it hardens in a few minutes. Glue is an invaluable cement for wood and many other purposes, it also joins any kind of broken glass or china that will not have to be subjected to much wetting. Shellac dissolved in spirit is a useful cement; and isinglass, dissolved in weak spirit, and having some gum ammonicum added to it, forms the “diamond cement” for uniting china. China and glass which require to be much wetted, are best united by being made very hot and having the broken edges rubbed with a piece of shellac, this melts on them, and forms, while hot, a sort of cement; if they be immediately applied and pressed firmly and accurately together, and then permitted slowly to cool, they will unite so as to be almost as strong as before breaking.
In various processes, cements of different descriptions are required for a variety of purposes. The common cement used in building, which is called mortar, is made of sand and quicklime mixed with water. Roman and Portland cements consist of certain kinds of clay burnt and ground. Plaster of Paris forms a useful cement, it is to be mixed with water to the consistence of cream, and it hardens in a few minutes. Glue is an invaluable cement for wood and many other purposes, it also joins any kind of broken glass or china that will not have to be subjected to much wetting. Shellac dissolved in spirit is a useful cement; and isinglass, dissolved in weak spirit, and having some gum ammonicum added to it, forms the “diamond cement” for uniting china. China and glass which require to be much wetted, are best united by being made very hot and having the broken edges rubbed with a piece of shellac, this melts on them, and forms, while hot, a sort of cement; if they be immediately applied and pressed firmly and accurately together, and then permitted slowly to cool, they will unite so as to be almost as strong as before breaking.
COKE.(‡ Coke Ovens.)Coke is produced by the partial burning of coal, in the same way that charcoal is from wood. The great source of coke is the gas manufactory, where it is sold in large quantities, being the result left in the retorts after the gas has all been driven off; but the consumption of coke by locomotive engines, &c., where coal would not be admissible on account of the smoke produced, has become so great that it is necessary to burn coals for its production; this is done by a range of ovens fitted up for that purpose, having iron doors which can be closed to any extent required so as to regulate the draught of air. Dr. Ure gives the following in his account of the coke ovens belonging to the London and North Western Railway Company:—“An excellent range of furnaces for making a superior article of coke for the service of the locomotive engines of the London and Birmingham Railway Company, has been erected at the Camden Town Station, consisting of eighteen ovens, in two lines, the whole discharging their products of combustion into a horizontal flue which terminates in a chimney-stalk one hundred and fifteen feet high. Each alternate oven is charged, between eight and ten o’clock every morning, with three-and-a-hall tons of good coals, a wisp of straw is thrown in on the top of the heap, which takes fire by the radiation from the dome, which is in a state of dull ignition from the preceding operation, and inflames the smoke then rising from the surface by the reaction of the hot sides and bottom upon the body of the fuel, in this way the smoke is consumed at the very commencement of the process, when it would otherwise be most abundant. The coke being perfectly freed from all fuliginous and volatile matters by a calcination of upwards of forty hours, is cooled down to moderate ignition by sliding in the dampers and sliding up the doors, which had been partially closed during the latter part of the process. It is now observed to form prismatic concretions, somewhat like a columnar mass of basalt. These are loosened by means of iron bars, lifted out upon shovels furnished with long iron shanks, which are poised upon swung chains with hooked ends, and the lumps are thrown upon the pavement, to be extinguished by sprinkling water upon them from the rose of a watering can, or they may be transferred into a large chest of sheet iron set on wheels, and then covered up. Good coals, thus treated, yield eighty per cent. of an excellent, compact, glistening coke, weighing fourteen cwt. per chaldron.”(‡ Oven Tools.)Coke burns without smoke, and not so rapidly by far as charcoal, it is, moreover, considerably cheaper than that article is.
(‡ Coke Ovens.)
Coke is produced by the partial burning of coal, in the same way that charcoal is from wood. The great source of coke is the gas manufactory, where it is sold in large quantities, being the result left in the retorts after the gas has all been driven off; but the consumption of coke by locomotive engines, &c., where coal would not be admissible on account of the smoke produced, has become so great that it is necessary to burn coals for its production; this is done by a range of ovens fitted up for that purpose, having iron doors which can be closed to any extent required so as to regulate the draught of air. Dr. Ure gives the following in his account of the coke ovens belonging to the London and North Western Railway Company:—“An excellent range of furnaces for making a superior article of coke for the service of the locomotive engines of the London and Birmingham Railway Company, has been erected at the Camden Town Station, consisting of eighteen ovens, in two lines, the whole discharging their products of combustion into a horizontal flue which terminates in a chimney-stalk one hundred and fifteen feet high. Each alternate oven is charged, between eight and ten o’clock every morning, with three-and-a-hall tons of good coals, a wisp of straw is thrown in on the top of the heap, which takes fire by the radiation from the dome, which is in a state of dull ignition from the preceding operation, and inflames the smoke then rising from the surface by the reaction of the hot sides and bottom upon the body of the fuel, in this way the smoke is consumed at the very commencement of the process, when it would otherwise be most abundant. The coke being perfectly freed from all fuliginous and volatile matters by a calcination of upwards of forty hours, is cooled down to moderate ignition by sliding in the dampers and sliding up the doors, which had been partially closed during the latter part of the process. It is now observed to form prismatic concretions, somewhat like a columnar mass of basalt. These are loosened by means of iron bars, lifted out upon shovels furnished with long iron shanks, which are poised upon swung chains with hooked ends, and the lumps are thrown upon the pavement, to be extinguished by sprinkling water upon them from the rose of a watering can, or they may be transferred into a large chest of sheet iron set on wheels, and then covered up. Good coals, thus treated, yield eighty per cent. of an excellent, compact, glistening coke, weighing fourteen cwt. per chaldron.”
(‡ Oven Tools.)
Coke burns without smoke, and not so rapidly by far as charcoal, it is, moreover, considerably cheaper than that article is.
GUNPOWDER.Gunpowder is a mixture of nitre, sulphur, and charcoal, and the more completely they are mixed, the more finely ground, and the purer they are, the more perfect will be the gunpowder. The proportions used of these ingredients differ slightly in different powder mills; but the average is about seventy-four parts nitre, ten sulphur, and fourteen charcoal, by weight; the sulphur and nitre can easily be completely purified, but the charcoal differs very much in almost every specimen, and charcoal that has been burnt long ago and exposed to the air and moisture is almost unfit for the purpose, that charcoal which has the least ash when burnt is found to be the best, and the charcoal which has been made in iron cylinders, is better than that made in the usual way, when each of the ingredients are separately powdered and sifted through a kind of sieve of silk called a bolting machine (such as is used in dressing flour), they are mixed in the proper proportions and taken to the mill, where they are moistened with water and ground to a smooth paste, this is pressed hard and then broken up into pieces which are put into a copper sieve, the bottom of which is perforated with small hole; a flat wooden ball is put into each sieve with the pieces of damp powder, and the sieves are all put into a circular motion by machinery, this causes the wooden ball to turn round in the sieve and so rub the damp powder through the little holes; it is collected below in small grains or “corns,” this process is called “corning,” this is now dried, and then put into a “reel” (a sort of barrel which turns round) and the grains, by rubbing against each other, become smoothed on the surface; the dust is now removed by a sieve, too fine to let the grains through; the powder is now fit for use.Gunpowder was first known in England about five hundred years ago. It is not only used to discharge firearms, but in the more peaceful occupations of quarrying stone, mining, and to get rid of rocks both below and above water; these processes are called “blasting.”
Gunpowder is a mixture of nitre, sulphur, and charcoal, and the more completely they are mixed, the more finely ground, and the purer they are, the more perfect will be the gunpowder. The proportions used of these ingredients differ slightly in different powder mills; but the average is about seventy-four parts nitre, ten sulphur, and fourteen charcoal, by weight; the sulphur and nitre can easily be completely purified, but the charcoal differs very much in almost every specimen, and charcoal that has been burnt long ago and exposed to the air and moisture is almost unfit for the purpose, that charcoal which has the least ash when burnt is found to be the best, and the charcoal which has been made in iron cylinders, is better than that made in the usual way, when each of the ingredients are separately powdered and sifted through a kind of sieve of silk called a bolting machine (such as is used in dressing flour), they are mixed in the proper proportions and taken to the mill, where they are moistened with water and ground to a smooth paste, this is pressed hard and then broken up into pieces which are put into a copper sieve, the bottom of which is perforated with small hole; a flat wooden ball is put into each sieve with the pieces of damp powder, and the sieves are all put into a circular motion by machinery, this causes the wooden ball to turn round in the sieve and so rub the damp powder through the little holes; it is collected below in small grains or “corns,” this process is called “corning,” this is now dried, and then put into a “reel” (a sort of barrel which turns round) and the grains, by rubbing against each other, become smoothed on the surface; the dust is now removed by a sieve, too fine to let the grains through; the powder is now fit for use.
Gunpowder was first known in England about five hundred years ago. It is not only used to discharge firearms, but in the more peaceful occupations of quarrying stone, mining, and to get rid of rocks both below and above water; these processes are called “blasting.”
GUN COTTON.To prepare gun cotton, make a mixture of three parts sulphuric acid and one part nitric acid; when this has cooled (for it becomes hot on mixing), put into it some cotton wool, and let it be stirred about with a glass rod, then taken out, and all the superfluous acid strained from it; it is then to be covered up for an hour or so. It should now be thoroughly washed in cold water, so that all the acid be removed; to ensure this completely, let it be afterwards washed in a very weak solution of potash, and then dried by a very gentle heat, produced by either steam or hot water; when dry, soak it in a solution of nitre and dry it again. It is now so explosive that great care is required in its management, being about three times as explosive as gunpowder.
To prepare gun cotton, make a mixture of three parts sulphuric acid and one part nitric acid; when this has cooled (for it becomes hot on mixing), put into it some cotton wool, and let it be stirred about with a glass rod, then taken out, and all the superfluous acid strained from it; it is then to be covered up for an hour or so. It should now be thoroughly washed in cold water, so that all the acid be removed; to ensure this completely, let it be afterwards washed in a very weak solution of potash, and then dried by a very gentle heat, produced by either steam or hot water; when dry, soak it in a solution of nitre and dry it again. It is now so explosive that great care is required in its management, being about three times as explosive as gunpowder.
PHOSPHORUS.This substance, since the general use of lucifer-matches, has become an important article of manufacture; whereas, but a few years ago, it was a mere chemical curiosity. It is prepared by mixing bone ashes with sulphuric acid, straining off the liquid part, and evaporating it to a syrupy consistence; with this, about a quarter of its weight of powdered charcoal is mixed, and the whole stirred and evaporated to a dry powder; this is put into earthenware retorts, which are connected by copper tubes to receivers filled with water; the retorts are raised to a white heat and maintained at this high temperature as long as any phosphorous passes into the receivers, the water in which is kept warm, so that the phosphorous melts and runs to the bottom, from whence it is taken and strained through chamois leather bags, under warm water, and then cast in glass tubes into sticks. Phosphorous is of a whitish color, like wax, is easily melted, readily takes fire even by slight friction, and, in the air, gives off fumes which in the dark appear luminous. It is chiefly used in the manufacture of lucifer matches, and, mixed with flour, butter, or sugar, is used to poison rats, mice, and other vermin, under the name of “phosphorous paste.” Phosphorous is poison, and most dangerous stuff to handle, minute particles often getting under the nails and causing painful sores.
This substance, since the general use of lucifer-matches, has become an important article of manufacture; whereas, but a few years ago, it was a mere chemical curiosity. It is prepared by mixing bone ashes with sulphuric acid, straining off the liquid part, and evaporating it to a syrupy consistence; with this, about a quarter of its weight of powdered charcoal is mixed, and the whole stirred and evaporated to a dry powder; this is put into earthenware retorts, which are connected by copper tubes to receivers filled with water; the retorts are raised to a white heat and maintained at this high temperature as long as any phosphorous passes into the receivers, the water in which is kept warm, so that the phosphorous melts and runs to the bottom, from whence it is taken and strained through chamois leather bags, under warm water, and then cast in glass tubes into sticks. Phosphorous is of a whitish color, like wax, is easily melted, readily takes fire even by slight friction, and, in the air, gives off fumes which in the dark appear luminous. It is chiefly used in the manufacture of lucifer matches, and, mixed with flour, butter, or sugar, is used to poison rats, mice, and other vermin, under the name of “phosphorous paste.” Phosphorous is poison, and most dangerous stuff to handle, minute particles often getting under the nails and causing painful sores.
WHITE LEAD.WHITE LEAD BED.(‡ Lead Grate.)FIG.1.White Lead is used in very large quantities by painters, not only as white paint, but to mix with and qualify every shade of color, and to give body to them. It is prepared by different processes, and several patents have been taken out for improvements in its manufacture; but the most usual, and, perhaps, the best process, is as follows:—Alayer of spent tan (from the tanner’s pits) is spread out three or four feet thick, and in it a number of earthen pots are arranged in rows, each partly filled with a mixture of vinegar, water, and treacle, or some other acid fermenting liquid, each of these pots is covered with a piece of lead made in the form of a grating (fig. 1), and over all these a flooring of boards, and then again a layer of tan, pots covered with lead, and boards, two or three times repeated; this is called a white lead bed, and is left for several weeks; the tan ferments and gets warm, causing the acid vapours to rise and corrode the lead, at the same time giving off carbonic acid. At the end of about three months the leaden covers are found to have become completely changed into a white shining substance (carbonate and oxide of lead), this is washed from impurities and ground in a mill, under water, to a fine powder. It is the white lead of commerce; but what is familiarly called white lead, is this substance ground up with linseed oil into a thick paste so as to be ready for the use of painters.White lead is a very poisonous substance, and produces the disease called painters’ colic, when taken into the system in minute quantities and for a long time, so that all who have much to do with this dangerous substance, as house-painters and artists, should be extremely careful that their hands are well washed frequently, and especially before going to meals.Cisterns of lead, used for containing water, very soon become coated inside with a thin film of sulphate of lead, this prevents the water from acting further on the lead, and the water from such cisterns is never found to be poisonous; but, if distilled water were used, it would act rapidly on the lead, corroding it, and causing a deposit in the water of white lead, which would render such water dangerous in the extreme.
WHITE LEAD BED.
WHITE LEAD BED.
(‡ Lead Grate.)FIG.1.
FIG.1.
White Lead is used in very large quantities by painters, not only as white paint, but to mix with and qualify every shade of color, and to give body to them. It is prepared by different processes, and several patents have been taken out for improvements in its manufacture; but the most usual, and, perhaps, the best process, is as follows:—Alayer of spent tan (from the tanner’s pits) is spread out three or four feet thick, and in it a number of earthen pots are arranged in rows, each partly filled with a mixture of vinegar, water, and treacle, or some other acid fermenting liquid, each of these pots is covered with a piece of lead made in the form of a grating (fig. 1), and over all these a flooring of boards, and then again a layer of tan, pots covered with lead, and boards, two or three times repeated; this is called a white lead bed, and is left for several weeks; the tan ferments and gets warm, causing the acid vapours to rise and corrode the lead, at the same time giving off carbonic acid. At the end of about three months the leaden covers are found to have become completely changed into a white shining substance (carbonate and oxide of lead), this is washed from impurities and ground in a mill, under water, to a fine powder. It is the white lead of commerce; but what is familiarly called white lead, is this substance ground up with linseed oil into a thick paste so as to be ready for the use of painters.
White lead is a very poisonous substance, and produces the disease called painters’ colic, when taken into the system in minute quantities and for a long time, so that all who have much to do with this dangerous substance, as house-painters and artists, should be extremely careful that their hands are well washed frequently, and especially before going to meals.Cisterns of lead, used for containing water, very soon become coated inside with a thin film of sulphate of lead, this prevents the water from acting further on the lead, and the water from such cisterns is never found to be poisonous; but, if distilled water were used, it would act rapidly on the lead, corroding it, and causing a deposit in the water of white lead, which would render such water dangerous in the extreme.
PRUSSIAN BLUE.This beautiful blue color is made by mixing solutions of sulphate of iron (green vitriol) and prussiate of potash together, when the Prussian blue falls in the form of a precipitate, or moist powder, of a pale greenish color, but which, by exposure to the air and the addition of a little nitric acid, becomes intensely blue; but the Prussian blue of commerce is never pure, for the solution of prussiate of potash is used as it comes from the factory, before being crystallized, and contains carbonate of potash, to get rid of which, alum is added, and the result is, the formation of a considerable amount of alumina, which is a white earth produced from the alum, and which falls down in the precipitate mixed with the Prussian blue, which is thereby increased in bulk and but little injured in color; when a larger quantity of this alumina is purposely produced, the result is a blue of a rather less intense color, called “Antwerp blue.” The chemical name for pure Prussian blue is percyanide of iron. Chinese blue is this substance in its purest state.
This beautiful blue color is made by mixing solutions of sulphate of iron (green vitriol) and prussiate of potash together, when the Prussian blue falls in the form of a precipitate, or moist powder, of a pale greenish color, but which, by exposure to the air and the addition of a little nitric acid, becomes intensely blue; but the Prussian blue of commerce is never pure, for the solution of prussiate of potash is used as it comes from the factory, before being crystallized, and contains carbonate of potash, to get rid of which, alum is added, and the result is, the formation of a considerable amount of alumina, which is a white earth produced from the alum, and which falls down in the precipitate mixed with the Prussian blue, which is thereby increased in bulk and but little injured in color; when a larger quantity of this alumina is purposely produced, the result is a blue of a rather less intense color, called “Antwerp blue.” The chemical name for pure Prussian blue is percyanide of iron. Chinese blue is this substance in its purest state.
PRUSSIATE OF POTASH.Prussiate of potash is the commercial name given to what chemists call “ferrocyanide of potassium,” it is used largely for the production of Prussian blue, and also in the art of electro-plating, which, of late, has greatly increased the demand for its manufacture, and many patents have been taken out for various modifications in the form of production, the result, however, is the same, and it occurs in commerce in magnificent crystals of a square form, with bevelled edges, and of a yellow color; there is, however, another kind called the “red prussiate,” which is much used in the process of calico printing. Prussiate of potash is made by heating together carbonate of potash, scraps of iron, and any kind of animal refuse, as blood, horns and hoofs, clippings of skin or old woollen rags; these are stirred together, and the heat raised, till they form a sort of paste of a black color, which, when cold, is thrown into water and all the soluble parts washed out; this fluid is filtered till quite clear, evaporated, and set aside that crystals may form; these are dissolved and again crystallized. The red prussiate is made by passing chlorine over the yellow prussiate in powder dissolving and crystallizing.The most deadly of all poisons, prussic or hydrocyanic acid, is obtained from the ferrocyanide of potassium, or prussiate of potash, by adding diluted sulphuric acid and distilling the vapour into an ice-cold receiver. This experiment should never be made by any but those well conversant with such matters.
Prussiate of potash is the commercial name given to what chemists call “ferrocyanide of potassium,” it is used largely for the production of Prussian blue, and also in the art of electro-plating, which, of late, has greatly increased the demand for its manufacture, and many patents have been taken out for various modifications in the form of production, the result, however, is the same, and it occurs in commerce in magnificent crystals of a square form, with bevelled edges, and of a yellow color; there is, however, another kind called the “red prussiate,” which is much used in the process of calico printing. Prussiate of potash is made by heating together carbonate of potash, scraps of iron, and any kind of animal refuse, as blood, horns and hoofs, clippings of skin or old woollen rags; these are stirred together, and the heat raised, till they form a sort of paste of a black color, which, when cold, is thrown into water and all the soluble parts washed out; this fluid is filtered till quite clear, evaporated, and set aside that crystals may form; these are dissolved and again crystallized. The red prussiate is made by passing chlorine over the yellow prussiate in powder dissolving and crystallizing.
The most deadly of all poisons, prussic or hydrocyanic acid, is obtained from the ferrocyanide of potassium, or prussiate of potash, by adding diluted sulphuric acid and distilling the vapour into an ice-cold receiver. This experiment should never be made by any but those well conversant with such matters.
SULPHATE OF IRON.Also called “Green Vitriol” and “Green Copperas,” is a combination of sulphuric acid and oxide of iron, and may be made by putting iron filings or pieces of iron into a mixture of sulphuric acid and water, and when all action has ceased evaporating the liquid, and setting it by till crystals form—these are of a pale green color. The sulphate of iron of commerce is formed by exposing the iron pyrites found in the coal districts to the air till it falls to powder; water is then poured over this substance, and the fluid collected and evaporated. Sulphate of iron is used chiefly to form the black dye so much in demand to dye cloth, and also in making writing ink.
Also called “Green Vitriol” and “Green Copperas,” is a combination of sulphuric acid and oxide of iron, and may be made by putting iron filings or pieces of iron into a mixture of sulphuric acid and water, and when all action has ceased evaporating the liquid, and setting it by till crystals form—these are of a pale green color. The sulphate of iron of commerce is formed by exposing the iron pyrites found in the coal districts to the air till it falls to powder; water is then poured over this substance, and the fluid collected and evaporated. Sulphate of iron is used chiefly to form the black dye so much in demand to dye cloth, and also in making writing ink.
SULPHATE OF COPPER.This substance is also known by the names, “Blue Vitriol” and “Blue Stone.” It is a combination of sulphuric acid with oxide of copper, and may be made by uniting those substances; but what is used on a large scale for commercial purposes is obtained from the waters which flow into copper mines where “copper pyrites” abound; this water is evaporated, and the sulphate of copper crystallizes. Sulphate of copper has of late been in great demand for the electro-deposition of copper.
This substance is also known by the names, “Blue Vitriol” and “Blue Stone.” It is a combination of sulphuric acid with oxide of copper, and may be made by uniting those substances; but what is used on a large scale for commercial purposes is obtained from the waters which flow into copper mines where “copper pyrites” abound; this water is evaporated, and the sulphate of copper crystallizes. Sulphate of copper has of late been in great demand for the electro-deposition of copper.
CHLORIDE OF LIME.Chloride of lime or “bleaching-powder” is made for the purposes of bleaching calicoes, linens, &c., and also for purifying foul air, which it does by giving out chlorine, a gas capable of uniting with and changing the injurious properties of foul air (which generally contains some combination of sulphur and hydrogen). Chloride of lime is made on the large scale by mixing hydrochloric acid with black oxide of manganese. This mixture gives off chlorine. This is made to pass over a layer of slaked lime, which absorbs it greedily, and becomes converted into the bleaching powder. The hydrochloric acid used is a product resulting from the manufacture of soda, and was formerly wasted; it is now used in large quantities for the process above described. “Burnett’s Disinfecting Fluid” is a solution of chloride of zinc. It is made by dissolving scraps of zinc in hydrochloric acid; hydrogen gas is given off, with effervescence, and the liquid remaining is the solution of chloride of zinc, which acts like chloride of lime, by giving off chlorine; for the chloride is slowly decomposed by the air, the oxygen of which takes the place of the chlorine, uniting with the zinc to form oxide of zinc, while the chlorine is set free.
Chloride of lime or “bleaching-powder” is made for the purposes of bleaching calicoes, linens, &c., and also for purifying foul air, which it does by giving out chlorine, a gas capable of uniting with and changing the injurious properties of foul air (which generally contains some combination of sulphur and hydrogen). Chloride of lime is made on the large scale by mixing hydrochloric acid with black oxide of manganese. This mixture gives off chlorine. This is made to pass over a layer of slaked lime, which absorbs it greedily, and becomes converted into the bleaching powder. The hydrochloric acid used is a product resulting from the manufacture of soda, and was formerly wasted; it is now used in large quantities for the process above described. “Burnett’s Disinfecting Fluid” is a solution of chloride of zinc. It is made by dissolving scraps of zinc in hydrochloric acid; hydrogen gas is given off, with effervescence, and the liquid remaining is the solution of chloride of zinc, which acts like chloride of lime, by giving off chlorine; for the chloride is slowly decomposed by the air, the oxygen of which takes the place of the chlorine, uniting with the zinc to form oxide of zinc, while the chlorine is set free.
SULPHURIC ACID.This was formerly called “Oil of Vitriol,” because it has an oily consistence, and was originally distilled from green vitriol. Sulphuric acid is one of the most useful chemical agents known; scarcely a process in chemical manufacture can be performed without its assistance. Sulphuric acid is colorless, and very heavy, being nearly double that of water (the proportion is 1·842, while water is 1,000); it is powerfully acid, even when largely diluted with water, and during this mixture with water gives out great heat, a mixture of equal parts will become hotter than boiling water; if it be mixed, however, with snow instead of water, it becomes extremely cold (below zero).Sulphuric acid is made by burning sulphur in a furnace, and causing the vapours to pass into a large chamber lined with lead, and having some water at the bottom; into this chamber the vapours arising from nitre mixed with sulphuric acid are also admitted, together with air and a jet of steam. These arrangements require to be properly and nicely regulated, and it was only by study of the complicated changes which take place between these gases (sulphurous acid, nitric oxide, and atmospheric air), that this arrangement has been devised and adopted, a great part of the product having been formerly wasted in a more clumsy mode of preparation. The sulphuric acid condensed in the water at the bottom of the leaden chamber is too weak for use, and is concentrated by evaporating the water from it; for this purpose it is placed in shallow leaden pans placed on the bars of a furnace, and finally distilled in glass retorts, or retorts of iron lined with platinum. Sulphuric acid has such a powerful attraction for water, that an open vessel half-full of strong acid placed in a damp situation will attract enough water from the atmosphere to cause it to be quite full before long. This power of attracting water has been taken advantage of to procure ice in those places where it is not to be had naturally, as India, &c. If a vessel of water be placed under the receiver of an air-pump, and the receiver exhausted of air, the vapour of the water will speedily fill it, taking the place of the air, and so stop any further evaporation; but if another vessel containing some sulphuric acid be placed also in the receiver, the acid will absorb the vapour of water as fast as it is formed, and this rapid evaporation continuing produces such cold, that the remaining water is shortly frozen. Iron and zinc dissolve rapidly in diluted sulphuric acid, giving off abundance of hydrogen gas, and this was the way this gas was formerly produced for the inflation of balloons, but the common coal-gas being easily obtainable in almost any quantity in all towns, it is now used for that purpose instead of hydrogen gas. Sulphuric acid (chemically considered) consists of 1 equivalent of sulphur with 3 of oxygen, and 1 of water. Pure sulphuric acid (without water) is in the form of fine crystals, much resembling snow, which, on exposure to air containing the slightest quantity of moisture, absorbs it, and becomes converted into the ordinary sulphuric acid.If this acid (even when greatly diluted) be spilt on cotton or linen it destroys it, producing a hole; this is owing to the acid converting the fibre into sugar. A proposition was once made to produce sugar from this source, but linen and cotton rags are in too great demand for paper-making to allow of its being done.
This was formerly called “Oil of Vitriol,” because it has an oily consistence, and was originally distilled from green vitriol. Sulphuric acid is one of the most useful chemical agents known; scarcely a process in chemical manufacture can be performed without its assistance. Sulphuric acid is colorless, and very heavy, being nearly double that of water (the proportion is 1·842, while water is 1,000); it is powerfully acid, even when largely diluted with water, and during this mixture with water gives out great heat, a mixture of equal parts will become hotter than boiling water; if it be mixed, however, with snow instead of water, it becomes extremely cold (below zero).
Sulphuric acid is made by burning sulphur in a furnace, and causing the vapours to pass into a large chamber lined with lead, and having some water at the bottom; into this chamber the vapours arising from nitre mixed with sulphuric acid are also admitted, together with air and a jet of steam. These arrangements require to be properly and nicely regulated, and it was only by study of the complicated changes which take place between these gases (sulphurous acid, nitric oxide, and atmospheric air), that this arrangement has been devised and adopted, a great part of the product having been formerly wasted in a more clumsy mode of preparation. The sulphuric acid condensed in the water at the bottom of the leaden chamber is too weak for use, and is concentrated by evaporating the water from it; for this purpose it is placed in shallow leaden pans placed on the bars of a furnace, and finally distilled in glass retorts, or retorts of iron lined with platinum. Sulphuric acid has such a powerful attraction for water, that an open vessel half-full of strong acid placed in a damp situation will attract enough water from the atmosphere to cause it to be quite full before long. This power of attracting water has been taken advantage of to procure ice in those places where it is not to be had naturally, as India, &c. If a vessel of water be placed under the receiver of an air-pump, and the receiver exhausted of air, the vapour of the water will speedily fill it, taking the place of the air, and so stop any further evaporation; but if another vessel containing some sulphuric acid be placed also in the receiver, the acid will absorb the vapour of water as fast as it is formed, and this rapid evaporation continuing produces such cold, that the remaining water is shortly frozen. Iron and zinc dissolve rapidly in diluted sulphuric acid, giving off abundance of hydrogen gas, and this was the way this gas was formerly produced for the inflation of balloons, but the common coal-gas being easily obtainable in almost any quantity in all towns, it is now used for that purpose instead of hydrogen gas. Sulphuric acid (chemically considered) consists of 1 equivalent of sulphur with 3 of oxygen, and 1 of water. Pure sulphuric acid (without water) is in the form of fine crystals, much resembling snow, which, on exposure to air containing the slightest quantity of moisture, absorbs it, and becomes converted into the ordinary sulphuric acid.
If this acid (even when greatly diluted) be spilt on cotton or linen it destroys it, producing a hole; this is owing to the acid converting the fibre into sugar. A proposition was once made to produce sugar from this source, but linen and cotton rags are in too great demand for paper-making to allow of its being done.
LEATHER.TAN-YARD AND PITS.Tanning is the name given to the process for converting the skins of animals into leather, by combining them with a substance called “Tannin.” This tannin exists in many vegetable substances, such as oak-bark, gall-nuts, catechu, sumach, &c.: all of these, and many more, are used for tanning, but, on account of its cheapness, oak-bark is the usual substance employed. It is tannin which gives the quality of astringency to many vegetables, and this very taste of astringency is produced by a partial combination of the tannin with the surface of the mouth.UNHAIRING THE SKIN.The skins (called “hides” or “pelts”) are first freed from all loose pieces of flesh, fat, or skin; the hair is then removed by soaking them in lime and water. The skins are then laid in the “tan-pit” between layers of crushed oak-bark until the pit is nearly full; water is then pumped in, and the whole is allowed to remain for several weeks or months (according to the thickness of the skin), during which time, however, the skins are changed in position by removing them from one pit to another with fresh bark in it, so that those taken from the top of the first are placed at the bottom of the next; and this is done from time to time, in order that all may receive the same pressure and strength of tan-liquor. Very thick hides take a year to tan perfectly in this way, and consequently many processes have been tried to quicken the operation; but the leather made most slowly seems to wear the best, and consequently fetches the higher prices.DRYING ROOMS.Skins which are thin, and to be used for fancy work, and for book-binding and glove-making, are either tanned with “sumach,” or with alum and salt made into a paste with flour and yolk of eggs; this is put into a tub, and the mixture and skins worked together with the hands till they are thoroughly united.SUMACH TAN TUBS.Besides boots and shoes, leather is used for the harness of horses, covers for seats, gloves, and innumerable other purposes.SPLITTING MACHINE.For some purposes the leather is required to be very thin, and of exactly one thickness. This is obtained by the process of splitting, for which a machine is used whose exactness is such, that one slice is taken from the inner part of the whole skin, reducing it in thickness without cutting a hole in any part. The skin is stretched tightly round a roller, which slowly revolves against a straight knife-edge, fixed at a certain distance from it, according to the thickness of the skin, and which is passed by the machine backwards and forwards, cutting the skin a little further each time.
TAN-YARD AND PITS.
TAN-YARD AND PITS.
Tanning is the name given to the process for converting the skins of animals into leather, by combining them with a substance called “Tannin.” This tannin exists in many vegetable substances, such as oak-bark, gall-nuts, catechu, sumach, &c.: all of these, and many more, are used for tanning, but, on account of its cheapness, oak-bark is the usual substance employed. It is tannin which gives the quality of astringency to many vegetables, and this very taste of astringency is produced by a partial combination of the tannin with the surface of the mouth.
UNHAIRING THE SKIN.
UNHAIRING THE SKIN.
The skins (called “hides” or “pelts”) are first freed from all loose pieces of flesh, fat, or skin; the hair is then removed by soaking them in lime and water. The skins are then laid in the “tan-pit” between layers of crushed oak-bark until the pit is nearly full; water is then pumped in, and the whole is allowed to remain for several weeks or months (according to the thickness of the skin), during which time, however, the skins are changed in position by removing them from one pit to another with fresh bark in it, so that those taken from the top of the first are placed at the bottom of the next; and this is done from time to time, in order that all may receive the same pressure and strength of tan-liquor. Very thick hides take a year to tan perfectly in this way, and consequently many processes have been tried to quicken the operation; but the leather made most slowly seems to wear the best, and consequently fetches the higher prices.
DRYING ROOMS.
DRYING ROOMS.
Skins which are thin, and to be used for fancy work, and for book-binding and glove-making, are either tanned with “sumach,” or with alum and salt made into a paste with flour and yolk of eggs; this is put into a tub, and the mixture and skins worked together with the hands till they are thoroughly united.
SUMACH TAN TUBS.
SUMACH TAN TUBS.
Besides boots and shoes, leather is used for the harness of horses, covers for seats, gloves, and innumerable other purposes.
SPLITTING MACHINE.
SPLITTING MACHINE.
For some purposes the leather is required to be very thin, and of exactly one thickness. This is obtained by the process of splitting, for which a machine is used whose exactness is such, that one slice is taken from the inner part of the whole skin, reducing it in thickness without cutting a hole in any part. The skin is stretched tightly round a roller, which slowly revolves against a straight knife-edge, fixed at a certain distance from it, according to the thickness of the skin, and which is passed by the machine backwards and forwards, cutting the skin a little further each time.
GLUE AND SIZE.Glue is made from the clippings of hides or any other refuse of skins, horn shavings, bones, &c. All these substances are piled up in a boiler having a second bottom within, perforated with holes, and kept from the true bottom by short feet; this arrangement is to prevent the substances boiled from burning at the bottom of the boiler. After many hours’ boiling the liquid is tested, and if it “sets” into a sort of jelly readily, the liquor is drawn off into another boiler, where it is kept warm, that it may not set till used. From this boiler it is strained through flannel into square wooden boxes, having ridges at the bottom dividing them into squares (to direct the workmen where to cut the glue when cold); these boxes are set apart, and when the contents have become cold and set into a firm jelly, a knife is passed between the sides of the box and its contents, and the glue turned out in a large solid square. This is now cut by means of a wire with a handle at each end into squares of about eight inches each way and an inch thick; these are now placed on nets made of cord fixed in frames one above another in a “drying-room,” which is open to the air at the sides, and able to be closed up in case of wet weather. In this room the glue dries up, shrinks, and hardens, until it is quite brittle; the marks of the net can be seen on every square of glue.Size is the same as glue, but instead of being dried it is put into small barrels. Two qualities of size are made, single and double size. It is much used by whitewashers, paper-hangers, and others, but for any purpose requiring good size, it may be made by soaking isinglass or gelatine in cold water till it is softened, and then standing the vessel in boiling water till it is dissolved; this produces a jelly nearly pure. A cheaper kind of size, almost as pure, may be made by boiling clippings of clean parchment till they are dissolved, and straining off the solution. Gelatine is the same as glue, but made of materials that are clean and fresh. Isinglass is the “sound” or swimming-bladder of the sturgeon, cleaned, dried, and cut up into fine shreds.
Glue is made from the clippings of hides or any other refuse of skins, horn shavings, bones, &c. All these substances are piled up in a boiler having a second bottom within, perforated with holes, and kept from the true bottom by short feet; this arrangement is to prevent the substances boiled from burning at the bottom of the boiler. After many hours’ boiling the liquid is tested, and if it “sets” into a sort of jelly readily, the liquor is drawn off into another boiler, where it is kept warm, that it may not set till used. From this boiler it is strained through flannel into square wooden boxes, having ridges at the bottom dividing them into squares (to direct the workmen where to cut the glue when cold); these boxes are set apart, and when the contents have become cold and set into a firm jelly, a knife is passed between the sides of the box and its contents, and the glue turned out in a large solid square. This is now cut by means of a wire with a handle at each end into squares of about eight inches each way and an inch thick; these are now placed on nets made of cord fixed in frames one above another in a “drying-room,” which is open to the air at the sides, and able to be closed up in case of wet weather. In this room the glue dries up, shrinks, and hardens, until it is quite brittle; the marks of the net can be seen on every square of glue.
Size is the same as glue, but instead of being dried it is put into small barrels. Two qualities of size are made, single and double size. It is much used by whitewashers, paper-hangers, and others, but for any purpose requiring good size, it may be made by soaking isinglass or gelatine in cold water till it is softened, and then standing the vessel in boiling water till it is dissolved; this produces a jelly nearly pure. A cheaper kind of size, almost as pure, may be made by boiling clippings of clean parchment till they are dissolved, and straining off the solution. Gelatine is the same as glue, but made of materials that are clean and fresh. Isinglass is the “sound” or swimming-bladder of the sturgeon, cleaned, dried, and cut up into fine shreds.
PARCHMENT.Parchment is prepared from the skins of sheep, goats, calves, and asses. Sheep-skins furnish by far the greater part of all parchment prepared, indeed all that which is used for deeds and law purposes. From whatever skin prepared, it is first soaked in lime and water to remove the hair and greasiness, and then stretched tightly on a frame, and the surface rubbed smooth with pumice-stone, after which the skin is allowed to dry. Parchment is used for deeds, which require to be very durable and not easily torn, both of which qualities it possesses much more than any kind of paper; it is also used for book-binding, drum-heads, and many other purposes. Clippings of parchment boiled for some time, and the liquid strained off, forms an excellent colorless size. Vellum is a thick kind of parchment, made chiefly of calf-skin.
Parchment is prepared from the skins of sheep, goats, calves, and asses. Sheep-skins furnish by far the greater part of all parchment prepared, indeed all that which is used for deeds and law purposes. From whatever skin prepared, it is first soaked in lime and water to remove the hair and greasiness, and then stretched tightly on a frame, and the surface rubbed smooth with pumice-stone, after which the skin is allowed to dry. Parchment is used for deeds, which require to be very durable and not easily torn, both of which qualities it possesses much more than any kind of paper; it is also used for book-binding, drum-heads, and many other purposes. Clippings of parchment boiled for some time, and the liquid strained off, forms an excellent colorless size. Vellum is a thick kind of parchment, made chiefly of calf-skin.