1. That of green oxide of iron for the oxygene of nitrous gas and water.2. That of the hydrogene of the water for the nitrogene of the nitrous gas.3. That of the principles of the sulphuric acid, for nitrogene and hydrogene.
1. That of green oxide of iron for the oxygene of nitrous gas and water.
2. That of the hydrogene of the water for the nitrogene of the nitrous gas.
3. That of the principles of the sulphuric acid, for nitrogene and hydrogene.
3dly. That at high temperatures, that is, from 200° to 300°, the equilibrium of affinity producing the binary combination between nitrous gas and solution of green sulphate of iron is destroyed; the attraction of the green oxide of iron for oxygene being increased; whilst probably that of nitrogene for hydrogene is diminished.
Hence the nitrous gas is either liberated,[123]in consequence of the affinity between oxygene and hydrogene, and oxygene and nitrogene not following the same ratio of alteration on increased temperature; or decomposed, because at a certain temperature the green oxide exerts such affinities upon water and nitrous gas, as to attract oxygene from both of them to form red oxide; whilst the still existing affinity between the hydrogene of the one, and the nitrogene of the other, disposes them to combine to form ammoniac.
4thly. That the change of color produced by introducing nitric acid to solution of common sulphate of iron, exactly analogous to that occasioned in it by impregnation with nitrous gas, is owing to the decomposition of the acid, by the combination of its oxygene with thegreen oxide of iron, and of its nitrous gas with the solution.
5thly. That nitrous gas in combination with solution of green sulphate of iron, is capable of exerting a strong affinity upon free or loosely combined oxygene, and of uniting with it to form nitric acid.
n.The products obtained from a solution of sulphate of iron saturated with nitrous gas, by Vauquelin and Humbolt, and their consequent mistake with regard to the nature of the process of absorption,[124]must have arisen from exposure of their impregnated solution to the atmosphere.
Indeed, from the acidity of it, on examination, from the small portion of ammoniac, and the large quantity of nitric acid obtained, it appears most probable that the whole of the nitrous gas employed was converted into nitric acid, by combining with atmospheric oxygene; for no nitricacid could have been obtained in the mode in which they operated, unless the green oxide of iron in the solution had been previously converted into red.
VIII.On the absorption of Nitrous Gas bysolution of green Muriate of Iron.
a.The analogy between the affinities of the constituents of the muriate and sulphate of iron, induced me to conjecture that they possessed similar powers of absorbing nitrous gas; and I soon found that this was actually the case; for on agitating half a cubic inch of solution of muriated iron, procured by dissolving iron filings in muriatic acid, in nitrous gas, the gas was absorbed with great rapidity, whilst the solution assumed a deep and bright brown tinge.
b.Proust,[125]who as I have before mentioned, supposes the existence of twooxides of iron only, one containing ²⁷/₁₀₀ oxygene, the other ⁴⁸/₁₀₀, has assumed, that the muriatic acid, and most other acids as well as the sulphuric, are capable of combining with these oxides, and of forming with each of them a distinct salt. He has, however, detailed no experiments on the muriates of iron.
As these salts are still more distinct from each other in their properties than the sulphates, and as these properties are connected with the phænomenon of the absorption and decomposition of nitrous gas, I shall detail the observations I have been able to make upon them.
c.When iron filings have been dissolved in pure muriatic acid, and the solution preserved from the contact of air, it is of a pale green color, and gives a white precipitate with alkaline prussiates. The alkalies throw down from it a light green oxide of iron.
When evaporated, it gives crystals almost white, which are extremely soluble in water; but insoluble in alcohol.
The solution of green muriate of iron has a great affinity for oxygene, and attracts it from the atmosphere, from nitric acid, and probably from oxygenated muriatic acid.
When red oxide of iron is dissolved in muriatic acid, or when nitric acid is decomposed by solution of green muriate of iron; the red muriate of iron is produced. The solution of this salt is of a deep brown red, its odor is peculiar, and its taste, even in a very diluted state, highly astringent. It acts upon animal and vegetable matters in a manner somewhat analogous to the oxygenated muriatic acid, rendering them yellowish white, or yellow.[126]
Sulphuric acid poured upon it, produces a smell resembling that of oxygenated muriatic acid. Evaporated at a low temperature, it gives an uncrystalisable dark, orange colored salt, which is soluble in alcohol, and when decomposed by the alkalies, gives a red precipitate. With prussiate of potash it gives prussian blue.
The common muriate of iron consists of different proportions of these two salts. It may be converted into red muriate by concentrated nitric acid, or into green by sulphurated hydrogene.
d.To ascertain if solution of red muriate of iron was capable of absorbing nitrous gas, I introduced into a jar filled with mercury, a cubic inch of nitrous gas, and admitted to it nearly half a cubic inch of solution of red muriate of iron. No discoloration took place. By much agitation, however, an absorption of nearly,2 was produced, and the solution became of a muddy green. But this change of color, and probably the absorption, was in consequence of the oxydation of either the mercury, or some imperfect metals combined with it, by the oxygene of the red muriate. For I afterwards found, that precisely the same change of color was produced when a solution was agitated over mercury.
e.I introduced to a cubic inch of concentrated solution ofgreen muriate of iron, 7 cubic inches of nitrous gas, free from nitric acid; the solution instantly became colored at the edges, and on agitation absorbed the gas with much greater rapidity than even sulphate of iron; in a minute, only a quarter of a cubic inch remained.
The solution appeared of a very dark brown, but evidently no precipitation had taken place in it, and the edges, when viewed against the light, were transparent and puce colored.
Five cubic inches more of nitrous gas were now dissolved in the solution. The intensity of the color increased, and after an hour no deposition had taken place. A little of it was then examined in the atmosphere; it had a much more astringent taste than the unimpregnated solution, and effected no change in red cabbage juice. When prussiate of potash was introduced into it, its color changed to olive brown. A few drops of the solution, that had accidentally fallen on the mercury, soon became colorless, and then effervesced with carbonate of potash, and tasted strongly acid.
The remainder of the impregnated solution, which must have nearly equalled,75 cubic inches, was introduced into a mattrass, having a stopper and curved tube, as in the experiments on the solution of sulphate of iron; great care being taken to preserve it from the contact of air.
The mattrass was heated by a spirit lamp, the curved tube being in communication with a mercurial cylinder. Near 8 cubic inches of nitrous gas were collected, when the solution became of a muddy yellow. It was suffered to cool, and examined. A small quantity of yellow precipitate covered the bottom of the mattrass; the fluid was pellucid, and light green. A little of it thrown on prussiate of potash, gave a white precipitate, colored by streaks of light blue. When the yellow precipitate was partly dissolved by sulphuric acid, a drop of the solution, mingled with prussiate of potash, gave a deep blue green.
Hence, evidently, the precipitate was red oxide of iron.
Caustic potash in excess was introduced into the remainder of the solution, and it was heated. It gave an evident smell of ammoniac, and dense white fumes, when held over strong phlogisticated nitrous acid.
When half of it was evaporated, sulphuric acid in excess was poured on the remainder; muriatic acid was liberated, not perceptibly combined with any nitric acid.
f.In an experiment that I made to ascertain the quantity of nitrous gas capable of combining with solution of green muriate of iron; I found that,75 cubic inches of saturated solution absorbed about 18 of nitrous gas, which is nearly double the quantity combinable with an equal portion of the strongest solution of sulphate of iron. A part of this impregnated solution, heated slowly, gave out more gas in proportion to the quantity it contained, than the last, and consequently produced less precipitate; so that I am inclined to suppose it probable, that at a certain temperature, all the dissolved nitrous gas may be dispelled from a solution.
From these experiments we may conclude,
1st. That the solution of green muriate of iron absorbs nitrous gas in consequence of nearly the same affinities as solution of green sulphate of iron; its capability of absorbing larger quantities depending most probably on its greater concentration (that is, on the greater solubility of the muriate of iron), and perhaps, in some measure, on a new combining affinity, that of muriatic acid for oxygene.
2dly. That at certain temperatures nitrous gas is either liberated from solution of green muriate, or decomposed, by the combination of its oxygene with green oxide of iron, and of its nitrogene with hydrogene, produced from water decompounded by the oxide at the same time.
IX.Absorption of Nitrous Gas bySolution of Nitrate of Iron.
a.As well as two sulphates and two muriates of iron, there exist two nitrates.[127]When concentrated nitric acid is made to act upon iron, nitrous gas is disengaged with great rapidity, and with great increase of temperature: the solution assumes a yellowish tinge, and as the process goes on, a yellow red oxide is precipitated.
Nitrate of iron made in this way, gives a bright blue mingled with prussiate of potash, and decomposed by the alkalies, a red precipitate. Its solution has little or no affinity for nitrous gas.
b.When very dilute nitric acid, that is, such as of specific gravity 1,16, is made to oxydate iron, without the assistance of heat, the solution gives out no gas for some time, and becomes dark olive brown: when neutralised it gives, decomposed by the alkalies, a light green precipitate; and mingled with prussiate of potash, pale green prussiate of iron.
It owes its color to the nitrous gas it holds in solution. By exposure to the atmosphere it becomes pale, the nitrous gas combined with it being converted into nitric acid.
It is then capable of absorbing nitrous gas, and consists of pale nitrate of iron, mingled with red nitrate.
I have not yet obtained a nitrate of iron giving only a white precipitate with prussiate of potash, that is, such as containsonlyoxide of iron at its minimum of oxydation; for when pure green oxide of iron is dissolved by very dilute nitric acid, a small quantity of the acid is generally decomposed, which is likewise the case in the decomposition of nitre by green sulphate of iron. The solutions of nitrate of iron, however, procured in both of these modes, absorb nitrous gas with rapidity, and by sulphurated hydrogene might probably be converted into pale nitrate.
As it is impossible to obtain concentrated solutions of pale nitrate of iron, chiefly containing green oxide, its powers of absorbing nitrousgas cannot be compared with the muriatic and sulphuric solutions, unless they are made of nearly the same specific gravity.
Nitrous gas is disengaged by heat from the impregnated solution of nitrate of iron, at the same time that much red oxide of iron is precipitated. Whether any nitrous gas is decomposed, I have not yet ascertained; for when unimpregnated pale nitrate of iron is heated, a part of the acid, and of the water of the solution, is decomposed by the green oxide of iron;[128]and in consequence ammoniac, and red nitrate of iron formed, whilst red oxide is precipitated.
X.Absorption of Nitrous Gas by otherMetallic Solutions.
a.White prussiate of iron in contact with water absorbs nitrous gas to a great extent, and becomes dark chocolate.[129]
b.Concentrated solution of sulphate of tin,probablyat its minimum of oxydation, absorbs one eighth of its bulk of nitrous gas, and becomes brown, without deposition.
c.Solution of sulphate of zinc absorbs about one tenth of its volume of nitrous gas, and becomes green.
d.Solution of muriate of zinc[130]absorbs nearly the same quantity, and becomes orange brown.
e.These are all the metallic substances on which I have experimented. It is more than probable that there exist others possessing similar powers of absorbing nitrous gas.
Whenever the metals capable of decomposing water exist in solutions attheir minimum of oxydation, the affinities exerted by them on nitrous gas and water, will be such as to produce combination. The powers of metallic solutions to combine with nitrous gas at common temperatures, as well as to decompose it at higher temperatures, will probably be in the ratio of the affinity of the metallic oxides they contain, for oxygene.
XI.The action of Sulphurated Hydrogene on solution ofGreen Sulphate of Iron, impregnated with Nitrous Gas.
a.In an experiment on the absorption of nitrous gas by solution of green sulphate of iron, I introduced an unboiled solution of common sulphate, deprived of red oxide of iron by sulphurated hydrogene, into a jar filled with nitrous gas; the absorption took place as usual, and nearly six of gas entered into combination, the volume of the solution being unity. On applying heat to a part of this impregnated solution, the whole of the nitrous gas it contained(as nearly as I could guess), was expelled undecompounded, and no yellow precipitate produced. Prussiate of potash poured into it gave only white prussiate of iron; and when it was heated with lime, no ammoniacal smell was perceptible.
I could refer this phænomenon to no other cause than to the existence of a small quantity of sulphurated hydrogene in the solution. That this was the real cause I found from the following experiment.
b.One part of a solution of green sulphate of iron, formed by the agitation of common sulphate of iron in contact with sulphurated hydrogene, was boiled for some minutes to expel the small quantity of gas retained by it undecompounded. It had then no peculiar smell, and gave a white prussiate of iron with prussiate of potash; the other part had a faint odor of sulphurated hydrogene, and gave a dirty white precipitate with prussiate of potash. Nearly equal quantities of each were saturated with nitrous gas, and heated. The unboiled impregnatedsolution gave out all its nitrous gas undecompounded; whilst in the boiled solution it was partly decomposed, yellow precipitate and ammoniac being formed.
c.This singular phænomenon of the power of a minute quantity of sulphurated hydrogene, in preventing the decomposition of nitrous gas and water, by green oxide of iron, will most probably take place in other impregnated solutions. It seems to depend on the strong affinity of the hydrogene of sulphurated hydrogene for oxygene.
XII.Additional Observations.
a.For separating nitrous gas from gases absorbable to no great extent by water; a well boiled solution of green muriate of iron should be employed. Nitrous gas agitated in this is rapidly absorbed, and it has no affinity for, or action on, nitrogene, hydrogene, or hydrocarbonate.
b.Nitrous gas carefully obtained from mercury and nitric acid,when received under mercury, or boiled water, and absorbed by solution of green muriate, or sulphate of iron, rarely leaves a residuum of ¹/₂₀₀ of its volume: preserved over common water, and absorbed, the remainder is generally from ¹/₄₀ to ¹/₉₀, from the nitrogene disengaged by the decomposition of the common air contained in the water.
c.The nitrous gas carefully obtained from the decomposition of nitric acid of 1,26, by copper, I have hardly ever found to contain more than from ¹/₃₀ to ¹/₅₀ nitrogene, when received through common water: when boiled water is employed, the residuum is nearly the same as that of nitrous gas obtained from mercury.
d.Consequently the gas from those two solutions may be used in common. It is more than probable, that the small quantities of nitrogene generally mingled with nitrous gas from copper and mercury, arise either from the common air of the vessels in which it was produced, or that of the water over which it was received. There is no reason for supposing that it is generated by a complete decomposition ofa portion of the acid.[131]
e.Whenever nitrous oxide is mingled with nitrous gas and nitrogene, it must be separated by well boiled water; and after the corrections are made for the quantity of air disengaged from the water, the nitrous gas absorbed by the muriatic solution.
EXPERIMENTS and OBSERVATIONS on the production of NITROUS OXIDE from NITROUS GAS and NITRIC ACID, in different modes.
I.Preliminaries.
a.
Theopinions of Priestley[132]and Kirwan,[133]relating to the causes of the conversion of nitrous gas into nitrous oxide, were founded on the theory of phlogiston. The first of these philosophers obtained nitrous oxide by placing nitrous gas in contact with moistened iron filings, or the alkaline sulphures. The last by exposing it to sulphurated hydrogene.
The Dutch chemists,[134]the latest experimentalists on nitrous oxide, have supposed that the production of this substance depends upon the simple abstraction of a portion of the oxygene of nitrous gas. They obtained nitrous oxide by exposing nitrous gas to muriate of tin, to copper in solution of ammoniac, and likewise by passing it over heated sulphur.
The diminution of volume sustained by nitrous gas during its conversion into nitrous oxide, has never been accurately ascertained; it has generally been supposed to be from two thirds to eight tenths.
b.Nitrous gas may be converted into nitrous oxide in two modes.
First, by the simple abstraction of a portion of its oxygene, by bodies possessing a strong affinity for that principle, such as alkaline sulphites, muriate of tin, and dry sulphures.
Second, by the combination of a body with a portion both of its oxygene and nitrogene, such as hydrogene, when either in a nascent form, or a peculiar state of combination.
c.Each of these modes will be distinctly treated of; and to prevent unnecessary repetitions, I shall give an account of the general manner in which the following experiments on the conversion of nitrous gas into nitrous oxide, have been conduced.
Nitrous gas, the purity of which has been accurately ascertained by solution of muriate of iron, is introduced into a graduated jar filled with dry mercury. If a fluid substance is designed for the conversion of the gas into nitrous oxide, it is heated, to expel any loosely combined air which might be liberated during the process; and then carefully introduced into the jar, by means of a small phial. After the process is finished, and the diminution accurately noted, the nitrous oxide formed is absorbed by pure water. If any nitrous gas remains, it is condensed by solution of muriate of iron; other residual gases are examined by the common tests. The quantity of nitrous oxide dissolved by the fluid is determined by a comparative experiment; and thecorrections for temperature and pressure being guessed at, the conclusions drawn.
If a solid substance is used, rather more nitrous gas than that designed for the conversion, is introduced into the jar. The substance is brought in contact with the gas, by being carried under the mercury; and as a little common air generally adheres to it, a small portion of the nitrous gas is transferred into a graduated tube, after the insertion, and its purity ascertained. In other respects the process is conducted as mentioned above.
II.Of the conversion of Nitrous gas into Nitrous Oxide,by Alkaline Sulphites.
The alkaline sulphites, particularly the sulphite of potash, convert nitrous gas into nitrous oxide, with much greater rapidity than any other bodies.
At temperature 46°, 16 cubic inches of nitrous gas were converted, inless than an hour, into 7,8 of nitrous oxide, by about 100 grains of pulverised sulphite of potash, containing its water of crystalisation. No sensible increase of temperature was produced during the process, no water was decomposed, and the quantity of nitrogene remaining after the experiment, was exactly equal to that previously contained in the nitrous gas.
The nitrous oxide produced from nitrous gas by sulphite of potash, has all the properties of that generated from the decomposition of nitrate of ammoniac. It gives, as will be seen hereafter, the same products by analysis. Phosphorus, the taper, sulphur, and charcoal, burn in it with vivid light. It is absorbable by water, and capable of expulsion from it unaltered, by heat.
Nitrous gas is converted into nitrous oxide by the alkaline sulphites with the same readiness, whether exposed to the light, or deprived of its influence.
The solid sulphites act upon nitrous gas much more readily than theirconcentrated solutions; they should however always be suffered to retain their water of crystalisation, or otherwise they attract moisture from the gas, and render it drier, and in consequence more condensed than it would otherwise be. In case perfectly dry sulphites are employed, the gas should be always saturated with moisture after the experiment, by introducing into the cylinder a drop of water.
The sulphites, after exposure to nitrous gas, are either found wholly, or partially, converted into sulphates. Consequently the conversion of nitrous gas into nitrous oxide by these bodies, simply depends on the abstraction of a portion of its oxygene; the nitrogene and remaining oxygene assuming a more condensed state of existence.
If we reason from the different specific gravities of nitrous oxide and nitrous gas, as compared with the diminution of volume of nitrous gas, during its conversion into nitrous oxide, 100 parts of nitrous gas, supposing the former estimation of the composition of nitrousoxide given inDivision III, accurate, would consist of 54 oxygene, and 46 nitrogene; which is not far from the true estimation. Or assuming the composition of nitrous gas, as given inDivision IV, it would appear from the diminution, that 100 parts of nitrous oxide consisted of 38 oxygene, and 62 nitrogene.
III.Conversion of Nitrous Gas into Nitrous Oxide,by Muriate of Tin, and dry Sulphures.
a.Nitrous gas exposed to dry muriate of tin, is slowly converted into nitrous oxide: during this process the apparent diminution is to about one half; but if the products are nicely examined, and the necessary corrections made, the real diminution of nitrous gas by muriate of tin, will be the same as by the sulphites; that is, 100 parts of it will be converted into 48 of nitrous oxide.
During this conversion, no water is decomposed, and no nitrogene evolved. Solution of muriate of tin converts nitrous gas into nitrous oxide; but with much less rapidity than the solid salt.
b.Nitrous gas exposed to dry and perfectly well made sulphures, particularly such as are produced from crystalised alumn[135]and charcoal not sufficiently inflammable to burn in the atmosphere, is converted into nitrous oxide by the simple abstraction of a portion of its oxygene, and consequently undergoes a diminution of ⁵²/₁₀₀.
It is probable, that all the bodies having strong affinity for oxygene will, at certain temperatures, convert nitrous gas into nitrous oxide. Priestley, and the Dutch chemists, effected the change by heated sulphur. Perhaps nitrous gas sent through a tube heated, but not ignited, with phosphorus, would be converted into nitrous oxide.
IV.Decomposition of Nitrous Gas, by Sulphurated Hydrogene.
a.When nitrous gas and sulphurated hydrogene are mingled together, a decomposition of them slowly takes place. The gases are diminished, sulphur deposited, nitrous oxide formed, and signs of the production of ammoniac[136]and water perceived.
In this process no sulphuric, or sulphureous acid is produced; consequently none of the sulphur is oxydated, and of course the changes depend upon the combination of the hydrogene of the sulphurated hydrogene, with different portions of the oxygene and nitrogene of the nitrous gas, to form water and ammoniac, the remaining oxygene and nitrogene assuming the form of nitrous oxide.
This singular exertion of attractions by a simple body, appears highly improbable a priori, nor did I admit it, till the formation of ammoniac, and the non-oxygenation of the sulphur, were made evident by many experiments.
In those experiments, the diminution of the nitrous gas was notuniformly the same. It varied from ¹¹/₂₀ to ¹⁴/₂₀. In the most accurate of them, 5 cubic inches of nitrous gas were converted into 2.2 of nitrous oxide. Consequently the quantity of ammoniac formed was,047 grains.
In experiments on the conversion of nitrous gas into nitrous oxide, by sulphurated hydrogene, the gases should be rendered as dry as possible. The presence of water considerably retards the decomposition.
b.The sulphures[137]dissolved in water convert nitrous gas into nitrous oxide. This decomposition is not, however, produced by the simple abstraction of oxygene from the nitrous gas to form sulphuric acid. It depends as well on the decomposition of the sulphurated hydrogene dissolved in the solution, or liberated from it. In this process sulphur is deposited on the surface of the fluid, sulphuric acid is formed, and the diminution, making the necessary corrections, is nearly the same as when free sulphurated hydrogene is employed.
It is extremely probable that sulphurated hydrogene, in combination with the alkalies, as well as with water, is capable of being slowly decomposed by nitrous gas.
V.Decomposition of Nitrous Gas by Nascent Hydrogene.
a.When nitrous gas, is exposed to wetted iron filings, a diminution of its volume slowly takes place; and after a certain time, it is found converted into nitrous oxide.
In this process ammoniac[138]is formed, and the iron partially oxydated.
The water in contact with the iron is decomposed by the combination of its oxygene with that substance, and of its hydrogene with a portion of the oxygene and nitrogene of the nitrous gas, to form water and ammoniac.
That the iron is not oxydated at the expence of the oxygene of the nitrous gas, appears very probable from the analogy between this process, and the mutual decomposition of nitrous gas and sulphurated hydrogene. Besides, dry iron filings effect no change whatever in nitrous gas, at common temperatures.
I have generally found about 12 of nitrous gas converted into 5 of nitrous oxide in this process; which is not very different from the diminution by sulphurated hydrogene. It takes place equally well in light and darkness; but more rapidly in warm weather than in cold.
b.Nitrous gas exposed to a large surface of zinc, in contact with water, is slowly converted into nitrous oxide; at the same time that ammoniac is generated, and white oxide of zinc formed. Thisprocess appears to depend, like the last, upon the decomposition of water by the affinities of part of the oxygene and nitrogene of nitrous gas, for its hydrogene, to form ammoniac and water; and by that of zinc for its oxygene. Zinc placed in contact with water, and confined by mercury,[139]decomposes it at the common temperature. Zinc, when perfectly dry, does not in the slightest degree act upon nitrous gas.
I have not been able to determine exactly the diminution of volume of nitrous gas, during its conversion into nitrous oxide by zinc. In one experiment 20 measures of nitrous gas, containing about,03 nitrogene, were diminished to 9, after an exposure of eight days to wetted zinc; but from an accident, I was not able to ascertain the exact quantity of nitrous oxide formed.
c.It is probable that most of the imperfect metals will be found capable of oxydation, by the decomposition of water, when itshydrogene is attracted by the oxygene and nitrogene of nitrous gas. I have this day (April 14, 1800), examined two portions of nitrous gas, one of which had been exposed to copper filings, and the other to powder of tin, for twenty-three days.
The gas that had been exposed to copper was diminished nearly two fifths. The taper burnt in it with an enlarged flame, blue at the edges. Hence it evidently contained nitrous oxide.
The nitrous gas in contact with tin had undergone a diminution of one fourth only, and did not support flame.
VI.Miscellaneous Observations on the conversionof Nitrous Gas into Nitrous Oxide.
a.Dr. Priestley found nitrous gas exposed to a mixture of iron filings and sulphur, with water, converted after a certain time, into nitrous oxide. Sulphurated hydrogene is always produced during the combination of iron and sulphur, when they are in contact with water;and by the hydrogene of this in the nascent state, the nitrous gas is most probably decomposed.
b.Green oxide of iron moistened with water, exposed to nitrous gas, slowly gains an orange tinge, whilst the gas is diminished. Most likely it is converted into nitrous oxide; but this I have not ascertained.
c.I exposed nitrous gas, to the following bodies over mercury for many days, without any diminution, or apparent change in its properties. Alcohol, saccharine matter, hydrocarbonate, sulphureous acid, and phosphorus.
d.Crystalised sulphate, and muriate of iron, absorb a small quantity of nitrous gas, and become dark colored on the outside; but after this absorption, (which probably depends on their water of crystalisation,) has taken place, no change is effected in the gas remaining.
e.The power of iron to decompose water being much increased by increase of temperature, nitrous gas is converted into nitrous oxide much more rapidly when placed in contact with a surface of heated iron,than when exposed to it at common temperatures. During the decomposition of nitrous gas in this way, ammoniac[140]is formed.
f.The curious experiments of Rouppe,[141]on the absorption of gases by charcoal, compared with the phænomena noticed in this Division, render it probable that hydrogene in a state of loose combination with charcoal, will be found to convert nitrous gas into nitrous oxide.
VII.Recapitulation of conclusions concerning theconversion of Nitrous Gas into Nitrous Oxide.
a.Certain bodies having a strong affinity for oxygene, as the sulphites, dry sulphures, muriate of tin, &c. convert nitrous gas into nitrous oxide, by simply attracting a portion of its oxygene; whilstthe remaining oxygene enters into combination with the nitrogene, and they assume a more condensed state of existence.
b.Nitrous gas is converted into nitrous oxide by hydrogene, in a peculiar state of existence, as in sulphurated hydrogene; and that by a series of very complex affinities. Both oxygene and nitrogene are attracted from the nitrous gas by the hydrogene, in such proportions as to form water and ammoniac, whilst the remaining oxygene and nitrogene[142]assume the form of nitrous oxide.
c.Nitrous gas placed in contact with bodies, such as iron and zinc decomposing water, is converted into nitrous oxide, at the same time that ammoniac is formed. It is difficult to ascertain the exact rationale of this process. For either the nascent hydrogene produced by the decomposition of the water by the metallic substance may combinewith portions of both the oxygene and nitrogene of the nitrous gas; and thus by forming water and ammoniac, convert it into nitrous oxide. Or the metallic substance may attract at the same time oxygene from the water and nitrous gas, whilst the nascent hydrogene of the water seizes upon a portion of the nitrogene of the nitrous gas to form ammoniac.
The degree of diminution, and the analogy between this process and the decomposition of nitrous gas by sulphurated hydrogene, render the first opinion most probable.
VIII.The production of Nitrous Oxide during theoxydation of Tin, Zinc, and Iron, in Nitric Acid.
a.Dr. Priestley discovered, that during the solution of tin, zinc, and iron, in nitric acid, certain portions of nitrous oxide were produced, mingled with quantities of nitrous gas, and nitrogene, varying in proportion as the acid employed was more or less concentrated.
It has long been known that ammoniac is formed during the solution of tin, zinc, and iron, in diluted nitric acid. Consequently, in these processes water is decomposed.
I had designed to investigate minutely these phænomena, so as to ascertain the quantities of water and acid decompounded, and of the new products generated. But after going through some experiments on the oxydation of tin without gaining conclusive results, the labor, and sacrifice of time they demanded, obliged me to desist from pursuing the subject, till I had completed more important investigations.
I shall detail the few observations which have occurred to me, relating to the production of nitrous oxide from metallic solutions.
b.When tin is dissolved in concentrated nitric acid, such as of 1.4, nitrous oxide is produced, mingled with generally more than twice its bulk of nitrous gas. In this process but little free nitrogene is evolved, and the tin is chiefly precipitated in the form of a white powder. If the solution, after the generation of theseproducts, is saturated with lime, and heated, the ammoniacal smell is distinct.
When nitric acid of specific gravity 1.24, is made to act upon tin; in the beginning of the process, nearly equal parts of nitrous gas and nitrous oxide are produced; as it advances, the proportion of nitrous oxide to the nitrous gas increases: the largest quantity of nitrous oxide that I have found in the gas procured from tin is ¾, the remainder being nitrous gas and nitrogene.
When tin is oxydated in an acid of less specific gravity than 1.09, the quantities of gas disengaged are very small, and consist of nitrogene, mingled with minute portions of nitrous oxide, and nitrous gas.
Whenever I have saturated solutions of tin in nitric acid of different specific gravities, with lime, and afterwards heated them, the ammoniacal smell has been uniformly perceptible, and generally most distinct when diluted acids have been employed.
c.When zinc is dissolved in nitric acid, whatever is its specific gravity, certain quantities of nitrous oxide are produced.
Nitric acids of greater specific gravity than 1.2, act upon zinc with great rapidity, and great increase of temperature. The gases disengaged from these solutions consist of nitrous gas, nitrous oxide, and nitrogene; the nitrous oxide rarely equals one third of the whole.
When nitric acid of 1,104 is made to dissolve zinc, the gas obtained in the middle of the process consists chiefly of nitrous oxide. From such a solution I obtained gas which gave a residuum of one sixth only when absorbed by water. The taper burnt in it with a brilliant flame, and sulphur with a vivid rose-colored light.
100 grains of granulated zinc, during their solution in 300 grains of nitric acid, of 1,43, diluted with 14 times its weight of water, produced 26 cubic inches of gas. Of this gas ⁷/₃₆ were nitrous, ¹⁷/₃₆36 nitrous oxide, and the remainder nitrogene. The solution saturated with lime and heated, gave a distinct smell of ammoniac.
d.During the solution of iron in concentrated nitric acid, the gas given out is chiefly nitrous; it is however generally mingled with minute quantities of nitrous oxide. When very dilute nitric acids are made to act upon iron, by the assistance of heat, nitrous oxide is produced in considerable quantities, mingled with nitrous gas and nitrogene; the proportions of which are smaller as the process advances.[143]The fluid remaining after the oxydation and solution of iron in nitric acid, always contains ammoniac.
e.As during the solution of tin, zinc, and iron, in nitric acid, the quantity of acid is diminished in proportion as the process advances, it is reasonable to suppose that the relative quantities of the gases evolved are perpetually varying. In the beginning of adissolution, the nitrous gas generally predominates, in the middle nitrous oxide, and at the end nitrogene.
f.During the generation of nitrous gas, nitrous oxide, and ammoniac, from the decomposition of solution of nitric acid in water, by tin, zinc, and iron, very complex attractions must exist between the constituents of the substances employed. The acid and the water are decomposed at the same time, and in proportions different as the solution is more concentrated, by the combination of their oxygene with the metallic body.
The nitrous gas is produced by the combination of the metal with ³²/₁₀₀ of the oxygene of the acid. The nitrous oxide is most probably generated by the decomposition of a portion of the nitrous gas disengaged, by the nascent hydrogene of the water decompounded; some of it may be possibly formed from a more complete decomposition of the acid.
The production of ammoniac may arise, probably from two causes; fromthe decomposition of the nitrous gas by the combination of the nascent hydrogene of the water, with portions of its oxygene and nitrogene at the same time; and from the union of hydrogene with nascent nitrogene liberated in consequence of a complete decomposition of part of the acid.
IX.Additional Observations on the productionof Nitrous Oxide.
a.When nitric acid is combined with muriatic acid, or sulphuric acid,[144]the quantities of nitrous oxide produced from its decomposition by tin, zinc, and iron, are rather increased than diminished. The nitrous oxide obtained from these solutions is, however, never sufficiently pure for physiological experiments. It is always mingled with either nitrous gas, nitrogene, or hydrogene, and sometimes with all of them.
b.From the solutions of bismuth, nickel, lead, and copper, in diluted nitric acid, I have never obtained any perceptible quantity of nitrous oxide: the gas produced is nitrous, mingled with different portions of nitrogene. Antimony and mercury, during their solution in aqua regia, give out only nitrous gas.
Probably none of the metallic bodies, except those that decompose water at temperatures below ignition, will generate nitrous oxide from nitric acid. On cobalt and manganese I have never had an opportunity of experimenting: manganese will probably produce nitrous oxide.
c.During the solution of vegetable matters[145]in nitric acid, by heat, very minute portions of nitrous oxide are sometimes produced, always however mingled with large quantities of nitrous gas, and carbonic acid.
When nitric acid is decompounded by ether, fixed oils, volatile oils, or alcohol, towards the end of the process small quantities of nitrousoxide are produced, and sometimes sufficiently pure to support the flame of the taper.[146]
d.When green oxide of iron is dissolved in nitric acid, nitrous oxide is produced, mingled with nitrogene and nitrous gas.
e.During the conversion of green sulphate, or green muriate of iron into red, by the decomposition of dilute nitric acid, nitrous oxide is formed, mingled with different proportions of nitrous gas and nitrogene.
f.When solution of green nitrate of iron is heated, a part of the acid is decomposed, red oxide is precipitated, red nitrate formed, and impure nitrous oxide evolved.
g.When iron is introduced into a solution of nitrate of copper, the copper is precipitated in its metallic state, whilst nitrous oxide, mingled with small portions of nitrogene, is produced.[147]
Both zinc and tin precipitate copper in its metallic form from solutionin the nitric acid. During these precipitations, certain quantities of nitrous oxide are generated, mingled however with larger quantities of nitrogene than that produced from decomposition by iron. In all these processes ammoniac is formed, and water consequently decomposed.
The decomposition of water and nitric acid, during the precipitation of copper from solution of nitrate of copper, by tin, zinc, and iron, depends upon the strong affinity of those metals for oxygene, and their powers of combining with a larger quantity of it than copper.
X.Decomposition of Aqua Regia by Platina, andevolution of a Gas analogous to OxygenatedMuriatic Acid, and Nitrogene.
a.De la Metherie, in his essay on different airs, has asserted that the gas produced by the solution of platina in nitro-muriatic acid, is identical with the dephlogisticated nitrous gas of Priestly.He calls it nitrous gas with excess of pure air, and affirms that it diminishes, both with nitrous gas and common air.
b.I introduced into a vessel containing 30 grains of platina, 2050 grains of aqua regia, composed of equal parts, by weight, of concentrated nitric acid of 1,43, and muriatic acid of 1,16. At the common temperature, that is, 49°, no action between the acid and platina appeared to take place. On the application of the heat of a spirit lamp, the solution gradually became yellow red, and gas was given out with rapidity. Some of this gas received in a jar filled with warm water, appeared of a bright yellow color. On agitation, the greater part of it was absorbed by the water, and the remainder extinguished flame. When it was received over mercury, it acted upon it with great rapidity, and formed on the surface a white crust.
As the process of solution advanced, the color of the acid changed to dark red, at the same time that the production of gas was much increased; more than 40 cubic inches were soon collected in the water apparatus.
Different portions of the gas were examined, it exhibited the following properties: