The Project Gutenberg eBook ofExperiments and Observations on the Following SubjectsThis ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.Title: Experiments and Observations on the Following SubjectsAuthor: Thomas HenryRelease date: June 29, 2014 [eBook #46143]Most recently updated: October 24, 2024Language: EnglishCredits: Produced by Les Galloway and the Online DistributedProofreading Team at http://www.pgdp.net (This file wasproduced from images generously made available by TheInternet Archive)*** START OF THE PROJECT GUTENBERG EBOOK EXPERIMENTS AND OBSERVATIONS ON THE FOLLOWING SUBJECTS ***
This ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.
Title: Experiments and Observations on the Following SubjectsAuthor: Thomas HenryRelease date: June 29, 2014 [eBook #46143]Most recently updated: October 24, 2024Language: EnglishCredits: Produced by Les Galloway and the Online DistributedProofreading Team at http://www.pgdp.net (This file wasproduced from images generously made available by TheInternet Archive)
Title: Experiments and Observations on the Following Subjects
Author: Thomas Henry
Author: Thomas Henry
Release date: June 29, 2014 [eBook #46143]Most recently updated: October 24, 2024
Language: English
Credits: Produced by Les Galloway and the Online DistributedProofreading Team at http://www.pgdp.net (This file wasproduced from images generously made available by TheInternet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK EXPERIMENTS AND OBSERVATIONS ON THE FOLLOWING SUBJECTS ***
ON THEFOLLOWING SUBJECTS;
BYTHOMAS HENRY,Apothecary.
Utut tamen se res habeat, ego bona saltem fide tradam quæ hactenus rescivi omnia.
Sydenham.
LONDON:Printed forJoseph Johnson, No. 72,St. Paul's Church-Yard.MDCCLXXIII.
TOThomas Percival, M.D. F.R.S. & S.A.
Dear Sir,
WHEN I reflect how much the friendship with which you have favoured me has contributed to my happiness; that from you has been imbibed a considerable share of the small taste I possess for experimental inquiries; andthat to your skilful and affectionate treatment I am greatly indebted even for the health I enjoy; it is impossible to hesitate a moment in the choice of a patron: gratitude and esteem direct me to inscribe this Treatise to you, and I chearfully obey their dictates. If to these any additional motive had been wanting, I should have received it from your having been an evidence to the result of many of the experiments related in the following pages.
That your own health may long enable you to continue exemplarily useful to your friends and to the public, is the sincere and ardent wish of,
Dear Sir,Your truly affectionateand very humble Servant,
Thomas Henry.
Manchester,18th Jan. 1773.
A RIGHT composition of the several articles used in medicine, is of so much importance to the practice of it, that every attempt to improve or ascertain the method of preparing them, cannot fail of a candid reception from the public.
Though great advancement has been made within these fewyears in chemical pharmacy, by the labours of the very ingenious Dr. Lewis, and some other writers on chemistry and the materia medica, there is still a wide field left for improvement. It is to be wished that Apothecaries, to whose province researches of this kind more peculiarly belong, and many of whom are well qualified by a liberal education to pursue them with advantage, would give their attention to these material interests of the art: for while the several professors of medicine and of surgery, are most laudably and assiduously employed in adding to the enlargement of these sciences, why should the sons of pharmacy remain supinelyinactive, and leave every thing towards the improvement of their profession to be performed by the members of the elder branch of physic, instead of contributingtheirshare to its support? as if tacitly acknowledging themselves unequal to the task, and thereby incurring the too general, though unmerited, imputation of want of knowledge and skill in their department.
The first part of the ensuing Treatise, which relatesan improved method of preparing Magnesia Alba, has been communicated to the College of Physicians; and that learned body have done the author the honour to insert it in the second volume of theirTRANSACTIONS. It is here reprinted as a proper introduction to the subsequent pages.
The calcination of Magnesia is not a new process[a]; but, as in this state it is a medicine not much introduced into practice, perhaps a few hints may be suggested, in regard to its medicinal and pharmaceutical properties, which are not generally known; and it is hoped thatsome useful information may be communicated relative to the various action of absorbent medicines on the bile.
In the succeeding chapters, it is attempted to determine how far, and in what proportion, lime promotes the solution of vegetable astringents, and other drugs in water; and whether the action of antiseptic medicines, thus dissolved, be in any degree impaired or increased by this mode of obtaining tinctures from them.
In endeavouring to contribute to the determination of the question, whether fixed air has the power of restoring sweetness toputrid substances, the Author may at first sight appear to have transgressed his proper limits; but, as fixed air, if possessed of this property, is likely to be a valuable acquisition to the materia medica, he flatters himself he shall incur no censure by the attempt.
Page 8, line 14, afterquantityreadof water.Page 10, line 18, forinterruptreadintercept.Page 13, line 1, readis there said.Page 16, line 1, readthe other absorbents.Page 29, note, line 4 from the bottom, foralbuminisreadaluminis.Page 31, line 4, forpatientsreadparents.Page 83, line 9, afterelegantreadgreen.Page 126, line 3, erase thecommaaftersmell.Page 127, line 3, place acommainstead of thesemicolon.
An account of an improved method of preparing MAGNESIA ALBA.
ALTHOUGHMagnesia Albais a medicine which has been in general use for many years, yet the proper mode of making it is very little known. Ourpharmacopæiaaffords us no information about it; and theformulawhich is given by the Edinburgh College, as well asthat with which the ingenious Doctor Black[b]has favoured us, is deficient in several circumstances. Hence the preparation of pure Magnesia has been confined to very few persons, who have preferred the emolument they have received by keeping their method secret, to the more diffusive utility of which a publication of it would have been productive.[c]I therefore beg leave to lay beforethe public a process for the preparation of Magnesia, by which it will be in the power of every Apothecary to make it himself, in all respects equal to that which is sold by those who conceal their method.
I am the more strongly induced to make this communication, because the Magnesia which is generally to be found in the shops, is either extremely coarse and ill prepared, or, which is still worse, sophisticated with calcareous substances, differing greatly from true Magnesia. I have been assured by some Physicians, that they have met with it mixed with chalk, and even with lime, and I have sometimes seen it so adulterated: a fraud of very dangerous tendency, as this powder is so frequently administered to very younginfants, and to adults of tender bowels and costive habits.
This medicine was originally prepared abroad, from the liquor called themother of nitre, which is composed of a light earth united with an acid; and these being separated, either by a strong fire, or by the addition of an alkali, the powder was washed in water, and obtained the name of Magnesia Alba. Hoffman afterwards prepared it from the bittern remaining after the crystallization of sea salt, which he found to be similar to the mother of nitre. And the factitious Epsom salt being prepared from this bittern, and evidently composed of Magnesia and the vitriolic acid, Dr. Black, who has favoured the world with a number of very valuable experiments on this subject, made use ofthis salt with success for the same purpose.
Happening some years ago to live in the neighbourhood of a gentleman who has long been celebrated as the preparer of the most genuine Magnesia, and never having been able myself to make Magnesia comparable to his, by the commonly known methods, I was desirous of gaining some intelligence as to his process, and was at last so fortunate as to obtain some useful hints.
I availed myself of these, and after repeated trials, produced Magnesia equally pure, white, tasteless, light and impalpable with that of Mr. Glass; nay sometimes that of my own preparing has been superiour to his, and in one respect has generally the advantage of it, namely, that mine isnot so stiff when dried, and may be reduced to the finest powder by simple pressure; whereashisrequires some degree of trituration to break the lumps effectually; which I imagine may be owing to his pursuing Dr. Black's method of drying it, by straining andpressingout the water through a cloth.
The following is the manner of preparing it, which I have found successful.
Dissolve any quantity ofsal catharticus amarus, commonly called Epsom salts, in its own weight of water; filter the liquor, and add to it by degrees a filtrated solution of pearl ashes in an equal quantity of water, stirring them gently until the mixed liquors have acquired the appearance of a complete coagulum: then cease adding anymore of the alkaline lixivium; and, having diluted the precipitate, and mixed it intimately with a small quantity of hot water, immediately throw the mixture into a large vessel of boiling water. Keep it boiling for a quarter of an hour, then take it out, and put it into glazed earthen vessels. As soon as the powder has subsided, and before the water be quite cold, pour it off, and add a fresh quantity of boiling water: repeat these ablutions with several parcels of hot water, till the liquor has entirely lost its saline taste. Then let it be so agitated as to suspend the finer parts of the powder; in which state decant it into other vessels, and having separated the water from the Magnesia by inclination, put it on large chalk stones, till a considerable part ofthe humidity be absorbed. Then wrap it up in sheets of white paper, and dry it before the fire. Pour hot water on the remaining powder, stir it, decant it in its turbid state, and separate the Magnesia from the water as before. By these means, the whole, or most of it, will be reduced to an equal degree of fineness.
The separation of the Magnesia will be promoted by heating the saline lixivia before they are mixed; and the larger the quantity or water into which the precipitated powder is cast, the more speedily and perfectly will the vitriolated tartar, which is formed by the alkali of thesal catharticus, be washed off. Dr. Black directs that three or four times the quantity of water, to that of the solutions, should be added; but this I have foundgreatly insufficient. The neutral salt should be washed off as quickly as possible; otherwise, as he justly observes, by allowing the mixture to stand for some time, the powder concretes into minute grains, which when viewed with a microscope, appear to be assemblages of needles diverging from a point. These concretions cannot be redissolved by any washing, however long continued. His intention, in boiling the mixture, is much better answered, by adding it to the water when in a state of ebullition; and once boiling in this manner is more effectual than a dozen washings in hot water.
Much depends on the purity of the water used in the process. If it be hard pump water, the selenites with which it is impregnated will be decompounded, andthe calcareous earth be deposited, after boiling; which mixing with the Magnesia will render it impure, gritty and discoloured. Rain water collected free from impurities, or clear river water, are most eligible; but if the situation of the operator does not permit him to procure these in a proper state, he should either use distilled water, which has been kept till the empyreuma is gone off, or at least such pump water as is free from any calcareous or saline impregnation. When poured on the Magnesia, it should be strained through a thick linen cloth, so as to intercept any accidental impurities which it may acquire in heating.
The drying should be performed with expedition. To this end, the chalk stones should be exposed to a moderate degree of heat; andwhen they have been employed two or three times, should be dried before a fresh quantity of the Magnesia is put on them. Cleanliness should be particularly attended to through the whole process; and the vessels ought to be carefully covered, that no dust may enter.
We may safely make use of a large copper brewing-pan, to boil the Magnesia in; for as the acid is perfectly neutralized, there can be no danger of its quitting the alkali, to which it has a greater affinity than to the metal; and copper does not readily dissolve, even in acids, when boiling hot; nor have I ever observed the least corrosion, though I have frequently used such vessels for this purpose.
Miscellaneous Observations.
SINCE the drawing up of the paper which has been the subject of the last chapter, some observations have occurred, which are either so immediately connected with, or at least deduced from it, that it may not perhaps seem inexpedient to introduce them in this place.
I was very much surprised to observe, in the Lectures lately published,as deliveredby the very learned and ingenious Dr. Cullen,that Magnesia is there said to be no more purgative than any other absorbent earth. The sentence is this; (speaking of other absorbents) "Magnesia alba should have been added to this set. It has had a considerable reputation as an absorbent, and when neutralized, as a purgative; but I find it is not more absorbent than any of the rest, nor more purgative in less quantity, as chalk or crab's eyes given in the same quantity, viz. dramij, will have the same effect. Therefore it may be neglected."
Surely this must have been an error of the person who wrote down the lectures, and have escaped the notice of the ingenious editors; who, from their skill in chemistry, must know that pure Magnesia differs from every calcareous or testaceous earth withwhich we are hitherto acquainted. These earths are nearly insoluble in the vitriolic acid, and what part does unite with it, forms a selenitical salt, the most difficult of solution of all others, and of an astringent nature: whereas the Magnesia[d]united with the same acid, produces what is commonly called Epsom salt, easy of solution, and purgative to the bowels. The former, with the nitrous acid constitutes a calcareous nitre, incapable of crystallization; with the marine acid a calcareous muriatic salt; and when dissolved in vinegar, the mixture spontaneously dries up into a friable sub-astringent salt: whereas Magnesia, with all these acids, formspurging salts; that with the nitrous acid, yellow, capable of being reduced into crystals retaining their form in a dry air, but melting in a moist one: with the muriatic acid, a salt is produced which does not crystallize, and easily melts when exposed to the air: with distilled vinegar, a saline uncrystallizable mass is formed, resembling glue both in colour and consistence while warm, but becoming brittle when cold. Dr. Black says, that two drachms of this salt purged a middle aged man four times; and half an ounce of the same gave a woman of a strong constitution no less than ten stools.[e]
Besides, where an acid prevails, much smaller doses than two drachms of Magnesia prove purgative; and it seldom happens thateven that dose of the other absorbents[f]will produce the same effect. Nor am I singular in my opinion, when I declare my doubt whether Magnesia be not of itself in some degree purgative, independent of its junction with any acid whatsoever. It appears to be an earthsui generis. That of alum resembles it in some respects, yet differs from it essentially, when combined with the vitriolic acid: the alum is strongly astringent and antiseptic, the Epsom salt purgative and septic.
I have very lately seen a paper signed by Doctor Cadogan and dated in the year 1767, in which he complains grievously of the advertisers of Magnesia, making use of his name without his consent, and has published the process for makinghisMagnesia. The doctor's intent in this was doubtless benevolent, but his manner of preparing this powder is unnecessarily expensive and wasteful. He directs only one pound of lixivium tartari to five pounds of sal catharticus amarus, which is greatly insufficient to precipitate all the Magnesia. And he insists strongly on the superiority of the lixivium prepared from salt of tartar, to that made of potashes, as if the chemical effects of one, were different from the other. But, says the Doctor, potashes render the Magnesia bitter. Surely the vitriolated tartar produced by a union of one vegetable fixed alkali with the vitriolic acid, is equally soluble in water with that prepared with any other, and if so, will be as easily washed off from the Magnesia.
But behold a champion steps forth, and at one blow levels to the ground the whole tribe of Magnesia makers, who have procured it from the factitious Epsom salts. I confess I have not had the happiness to peruse this ingenious gentleman's pamphlet on the subject, but I have formed a very extraordinary opinion of hiscandour,modesty,and knowledge, from the very curious paper which he distributes with his Magnesia. Notwithstanding Doctor Black, and since him Mr. Glass and several others, have procuredpureMagnesia from the factitious Epsom salts, Mr. Dale Ingram, assures us, that he has made an improvement, "which is by the learned esteemed one of the greatest acquisitions to the materia medica." And wherein does this mighty discovery consist? even that Magnesia prepared from the waters of Epsom, is superiour to that prepared from the bitterpurging salt; and he assures us that the Magnesia sold by him is so prepared.
To the first assertion I shall only reply, that every person at all conversant in chemistry knows that Magnesia earth is the same, from whatever substance it can be separated in a pure state; that the factitious Epsom salt yields it in as great a degree of purity as the salt of the Epsom water, and that Dr. Alston assures us, the artificial salt "by various and repeated experiments, made in France as well as in Britain, is demonstrated to be every way as good as, yea to be the very same with, the genuine made of the Epsom waters."[g]
As to the other declaration, itwill be sufficient to observe that one gallon of Epsom water contains only seven drachms of salt in a dry season, and hardly six drachms in a wet one;[h]and that for this salt to precipitate its Magnesia properly, it is necessary it should be diluted with little more than its own weight of water.[i]Six drachms of salt will yield two drachms of Magnesia. So that to procure a pound of this powder Mr. Ingram must evaporate above sixty gallons of the water, to between five and six pints, before he begins the precipitation. Sure never did empiricism appear so thinly disguised!
In the preceding chapter, the necessity of using water free from any calcareous impregnation hasbeen particularly insisted on, and I have, on another occasion,[j]observed that great attention should be given to the purity of the water used in the making of all the saline preparations; and I may add in almost all the operations of pharmacy. Dr. Percival, in his ingenious experiments on water, found a quart of the Manchester pump water to contain upwards of sixty grains of adventitious matter.[k]Suppose therefore, for instance, that in making the extract from a pound of peruvian bark, it be boiled only six times in the quantity of water directed by the London Dispensatory, nine gallons will be consumed in the process; which is a very moderate allowance, six coctionsnot being sufficient to extract all the virtues of that drug. Dr. Percival boiled half an ounce of bark twenty five times, in so many different pints of water, the last of which had some impregnation, and the residuum gave a deep colour, and considerable bitterness to rectified spirit of wine. If we likewise suppose only one half of the foreign contents of such water to be left by evaporation, then the quantity of calcareous and saline matter, undesignedly mixed with the extract, will be two ounces and two drachms, or nearly equal to the quantity of extract procured from a pound of bark by pure water. Thus this important medicine becomes grossly adulterated, without any such intention in the operator; and Iknow it is the common practice to use pump water in making it.
I have particularly selected the Peruvian bark, as requiring a very large quantity of water to extract the whole which it is capable of yielding; but the proportion of water which I have here allowed, will not be too great in obtaining extracts from most vegetable substances; and how greatly not only the quantity, but the quality of the medicine must be affected by the admixture of such a weight of insoluble calcareous earth, is so obvious, that it is needless to expatiate on it.
On the medicinal properties ofMAGNESIA ALBA.
THE medicinal uses to which Magnesia has hitherto been applied are in general so well known, that it will be necessary only to give a short summary of the cases in which it is beneficial, for the information of young practitioners, and of those of my readers who may not be acquainted with medical subjects, this medicine being frequently administered without the advice of a physician. If it should appear in the subsequent part of this treatise that Magnesia is possessed of any properties hitherto unsuspected in it, the sagacious reader will in a great measure be left to draw his own practical inferences therefrom.
Magnesia Albais a powerful absorbent, and is given with great success in disorders of the stomach and bowels arising from acidity. This preparation had been introduced into the materia medica abroad several years before it attracted the attention of our countrymen. The celebrated Hoffman having strongly recommended it to the medical world, some English practitioners began to prescribe it, and Dr. Cadogan bestowing high encomiums on it, in his treatise on the nursing andmanagement of children, it soon made its way into general practice, and supplied the place of the testaceous powders and chalk, which before this period were the medicines usually given to correct acidities in the primæ viæ. The acquisition of this medicine was of the more importance, on account of its entire and easy solution in acids, and of the purgative quality which it possesses; whereas the common absorbents are apt to form concretions, and to induce costiveness; strong objections to their free exhibition, as these properties render them peculiarly unfit for the bowels of tender infants who are particularly liable to diseases of this class.
This tendency to acidity generally attends children during the first months and the time ofdentition, and discovers itself when too redundant by the green stools, sour vomitings, gripes and purgings which it occasions: and as the nerves of children are extremely irritable, spasmodic affections are often the consequence of this acrid stimulus being retained in their bowels. In these cases Magnesia may be administered in doses from five to twenty or thirty grains, according to the age of the infant; and in proportion as it is intended to act, either as an alterative, or as an easy purgative.
It has been a common practice to give Magnesia to children as a preventive, and to mix it for this purpose with their food, in order to correct that disposition which milk and the farinaceous aliments have to turn sour. This however should be done with caution,for it is only the excess of acidity which is prejudicial to infants,[l]some degree of it is necessary; and should we too officiously and entirely destroy, what we ought only to restrain within due bounds, we may create disorders of an opposite nature to those we have endeavoured to prevent, and instead of an acid, produce an alkalescent disposition in the first passages. Indeed I fear that diseases have been more frequently created than obviated by the use of preventive medicines, and they should only be allowed in cases where the approach to disease is manifest. But when a child is in a healthy state, the best means to preserve him from a superabundant acidity, is to pay due attention to the regulation of his diet, to give him proper exercise, not to confine him too much in the foul air of hot unventilated rooms, to wash his whole body every day in cold water, and to rub him very well night and morning with a dryflannel, taking care that his stomach be not too full at the time when this friction is performed.
Nor would I advise parents to rely with too much security on the virtues of this medicine, where the disorders of their children are complicated, or obstinate. The advice of the sagacious and distinguishing practitioner will then be necessary to direct what method of treatment is to be pursued. Nor can I here avoid lamenting that the management of children when diseased, is so often in the hands of nurses and ignorant women, from an absurd notion that their diseases are not proper subjects of medical investigation; when in truth, there are none which require a clearer judgement, a quicker penetration, or a greater share of medical knowledge in the prescriber.
During the period between dentition and puberty, the diseases attendant on a lax fibre still continue, though not so predominantly as in the former stage; yet acescency is the manifest cause, or at least the concomitant of many of the complaints to which children are at this time liable. To this they are disposed, notwithstanding the change in their diet to a more alkalescent kind, by the great quantities of fruit, frequently crude and unripe, cakes, and other sweet and greasy food with which they are too often indulged. By these errors their bowels are overcharged, their digestion impaired, and the aliment remaining too long in the stomach becomes sour, and occasions vomitings, head achs, and other complaints which are often thoughtto proceed from worms, and indeed are frequently attended with that disorder; as the crudities thus generated in the bowels serve as a nidus for these destructive vermin. Here likewise Magnesia may be of considerable advantage as an alkaline purgative, neutralizing the offending acid, and at the same time promoting its discharge by stool. But if the stomach be overloaded with mucus or undigested aliment, a gentle vomit ought to precede the exhibition of the Magnesia.
And even in a more advanced stage of life, persons of weak habits, and who lead sedentary lives, are often afflicted with indigestion, sour eructations, heart-burn, vomitings, and costiveness. These disorders very frequently attend women during their state of pregnancy, and are sometimes almost instantly removed by the use of Magnesia. Dr. Watson[m]has published the case of a pregnant woman, who was afflicted with such severe vomitings as to bring on convulsions, hiccoughing, and violent pain at her stomach. What she brought up was acid, and so very acrimonious, as to inflame and excoriate her mouth and throat; and the great uneasiness she felt at her stomach upon swallowing any liquor that had the least degree of acrimony, or was more than lukewarm, made it probable that the internal surface of the stomach was affected in the same manner. In this desperate situation, after a variety of remedies had been tried in vain, the stomach was washed with unsalted mutton broth, till the liquor was discharged without any acid taste. Her pain was by this means abated, but in about two hours was apparently returning with the same violence as before. This ingenious Physician then directed a drachm of Magnesia to be given in mutton broth, and to be repeated as often as her pain returned, without any regard to the quantity the whole might amount to, supposing her pain to continue severe. The first dose relieved her, and in three days she took three ounces of Magnesia; and in the next three days, two ounces more, by which time all her symptoms were removed. It is remarkable in this case that a hypercatharsis was not the consequence of taking so large a quantity of Magnesia, where there was so much acid to neutralize it.
In bilious habits, where there is generally a disposition in the stomach contrary to acidity, Magnesia is usually esteemed to be improper, taken alone: but I am dubious whether this opinion is well founded, and many reasons for these doubts may be deduced from the experiments hereafter to be recited. However, where putrid bile is to be corrected and discharged, by stool, very good purposes may, perhaps, be answered by taking the Magnesia, joined with a sufficient quantity of acid to neutralize it, while in a state of effervescence; or by swallowing the Magnesia and the acid, one immediately after the other, so as to produce the fermentation in the stomach: for thus the fixedair with which the Magnesia so greatly abounds, being let loose, may powerfully correct the tendency to putridity in the contents of the primæ viæ, and at the same time evacuate them downwards.
How far Magnesia may be of service in diseases of the skin I do not take upon me to determine. Several authors have attributed cutaneous eruptions, and indeed the ancient chemists ascribed almost all disorders, to the presence of an acid in the blood; whilst others absolutely deny that an acid can be admitted into the lacteals, or, if admitted, exist in the blood in a state of acidity. In these cases however, if an acid acrimony abounds in the stomach and bowels, with a costive habit, and pale complexion, Magnesia will be a useful corrector, and entering intothe circulation in the form of a mild neutral salt, may act as an excellent alterative,[n]proving both diaphoretic and diuretic.
Having thus given a cursory detail of the medicinal properties of Magnesia, in its natural state, I shall now proceed to consider it in a state of calcination: but before any description of its uses in medicine be given, it may be proper to take a view of the changes which are produced in the nature of it by this operation.
On the calcination ofMAGNESIA ALBA.
THE free spirit of inquiry, and taste for experimental researches which have of late so happily prevailed, have given rise to several very important discoveries in the course of the last half century; among which, those of the properties of the electrical fluid, and of fixed air, hold a principal rank. That excellent philosopher and experimentalist,the late Doctor Hales, first proved that most bodies contain, as one of their component principles, a quantity of air, differing from that of the common atmosphere in several of its properties. The proportion of this element varies in different substances, and in some constitutes nearly one half of their weight. All calcareous earths, the testaceous powders, Magnesia and alkaline salts contain it abundantly, and have the strongest affinity with it of any bodies, except metals. From all these it is discharged by an acid, and the stronger the acid is, the more sudden and plentiful is the discharge of this vapour, which is of the same nature as that emitted by fermenting liquors. Though it may be inspired in small quantities with impunity, and, as appears from some late observations, even withadvantage in some cases,[o]yet it is a known fact that animals expire sooner in a receiver filled with fixed air, than in vacuo. Lastly, it is said to have the remarkable property of rendering putrid substances sweet.
In the precipitation of Magnesia, the acid of the Epsom salt uniting with the alkali which is added to the solution, expels the fixed air which the latter contains; but the vapour instead of being dissipated as in the common effervescing mixtures of acids and alkalis, is quietly and immediatelyabsorbed by the Magnesia earth, to which it has a strong affinity; and thus a double elective attraction takes place.
The very large proportion of this element contained in Magnesia Alba has given Dr. Black an opportunity of throwing much light on this hitherto obscure subject; and that excellent chemist has drawn such inferences from the result of his experiments on Magnesia, Quick-lime, and other alkaline substances, as are of the utmost importance to chemistry. As this treatise may fall into the hands of several who may not have an opportunity of perusing the valuable Essays in which these experiments are contained, I shall take the liberty to make a short extract from them, in order to elucidate the subject of the subsequent pages.
The first object of Dr. Black's enquiry was, whether Magnesia could be reduced to Quick-lime. To this purpose, he calcined an ounce of Magnesia in a strong fire. When taken out of the crucible and weighed, it had lost seven twelfths of its weight. Combined with different acids, it formed salts of a similar nature to those constituted by the same acids with the uncalcined powder; but dissolved in them without the least degree of effervescence.
It slowly precipitated the corrosive sublimate of mercury, in the form of a black powder; whereas before calcination a dark red precipitate was formed from the same substance. Mixed with a warm solution of salt ammoniac, it separated the volatile alkali from the acid; but it made no separation of an acid from a calcareous earth, nor did it induce any change upon lime-water; whereas in an uncalcined state, it rendered quick-lime mild. Lastly, being digested for some hours with water, it produced not the least alteration in the water.[p]
In pursuing his inquiries, he found that a very small portion ofwhat had been lost in the calcination was water, and that the other part was fixed air, by the loss of which the Magnesia was deprived of its power of effervescing with acids. And from hence the Doctor concluded, that the change made in calcareous substances and in Magnesia by calcination, was chiefly produced by depriving them of this air; and that this volatile Proteus may be conveyed from one body containing it to another body with which it has a greater affinity.
Thus lime being deprived of its air by calcination, and having a stronger affinity with it than alkaline salts have, being mixed with a lixivium of these salts, absorbs all the air from them, deprives them of their property of effervescing with acids, and rendersthem more acrid, at the same time that the lime becomes mild, and incapable of impregnating water, but recovers its power of fermenting when mixed with an acid.
On the medicinal virtues ofCALCINED MAGNESIA.
FREQUENT objections have been made to the use of Magnesia Alba, on account of the great quantity of air which enters into its composition. Whenever it meets with an acid in the stomach they immediately unite; but in forming this union, all the air contained in the Magnesia is discharged with a great degree of effervescence, and recovering itselasticity sometimes occasions very uneasy sensations in weak bowels,[q]inflating and distending them overmuch, inducing griping pains, and above all a sense of debility or sinking, which is not easily described.
My much respected friend Doctor Percival, who had often complained of these disagreeable effects from the use of Magnesia, suggested to me the idea of depriving it of its fixed air by calcination, having been informed that they would be obviated by this method. Doctor Black had indeed proved the practicability of the process, but he does not appear to have made trial of the calcined Magnesia as a medicine. In consequence of the above hint I calcined some Magnesia, and was afterwards insensibly led to make further experiments, the event of which, I hope, will be deemed of sufficient importance to apologize for my communicating them to the public.
EXPERIMENT I.
Eight ounces of pure Magnesia Alba were calcined with a strong fire in an air furnace. Three hours calcination were necessary to discharge the whole of the air from the Magnesia. When removed from the fire, it had lost four ounces and three drachms of its original weight, and produced no effervescence with acids; it had not acquired any degree of acrimony to the taste, and when thirty grains of it were diluted with a few spoonfuls of water and swallowed, it occasioned no uneasy sensation in my stomach, nor sense of heat in my throat; proved nearly as aperient as a double quantity of uncalcined Magnesia, and operated without the least griping. It was remarkable that calcination had not reduced the powder in bulk, in proportion to the diminution of its weight.
By the process of this experiment, Magnesia Alba is not only divested of the disagreeable qualities which have been alluded to,but acquires new properties which render it likely to answer some very important practical purposes.
Doctor Macbride, who has with the greatest ingenuity and accuracy, prosecuted the investigation of the nature of fixed air, discovered, that a large quantity of it is discharged in the fermentation of alimentary mixtures; and that the saliva being, in a healthy state, void of air, acts as an absorbent of it, thereby moderating and restraining the discharge of this vapour in the stomach. But when the tone of that viscus is too relaxed to perform the digestion of the aliment with proper vigour, or the saliva is diseased and corrupted, the air expelled from the food becomes too elastic, and produces those disorders which are commonly termed flatulent; and,perhaps, by its effects on that prodigious plexus of nerves which is diffused over the coats of the stomach, may sometimes occasion spasmodic or paralytic affections.
It has been observed above, that calcareous earths, alkaline salts, and Magnesia, being deprived of their air, attract it from every substance with which it has a smaller degree of affinity. The two former becoming highly caustic by the loss of their air cannot be administered but in very small doses. But the calcined Magnesia being absolutely divested of air, though not rendered acrimonious, and being able to absorb a large quantity of this elastic flatus, may act more powerfully than the whole tribe of carminatives, yet essentially differs from them in many respects.Theycontain alarge quantity of air;Magnesiain this state is entirely free from it;Aromaticsmay be apt to ferment, and increase acidities; thecalcined Magnesiais incapable of effervescence, and powerfully corrects an acescent disposition in the gastric juices; theformerconstipate the belly; thelatteris laxative.
From this property of Magnesia, when calcined, of absorbing air, it occurred to me, that it would of all others be the most proper cathartic for patients labouring under the stone, who might be taking the lixivium saponarium, having the advantage over all the vegetable purgatives, which abound with air, and consequently have a tendency to render the caustic alkali mild and inert. I even flattered myselfthat it might coincide in promoting the efficacy of that powerful solvent of the human calculus. Dr. Macbride's theory, that the lixivium acts by depriving the calculus of its fixed air, appears to be well founded; and Mr. Chittick in the exhibition of his nostrum, which, notwithstanding all his empirical arts to disguise it, is now known to have been the soap ley, kept his patients from every kind of diet abounding with air. We may therefore venture to recommend it, though not as a lithontriptic, being insoluble in water, yet as an assistant to the lixivium, by absorbing a part of that air in the primæ viæ which would otherwise be attracted by the caustic alkali, and thereby render it incapable of acting on the calculus.
In all the diseases attended with an acescent disposition in the first passages, in which Magnesia has been recommended in the third chapter, the calcined powder may be given with superiour advantages, as it will not produce any of those inconveniences, which have been attributed to that medicine when uncalcined. Besides that it will act in a three-fold capacity, viz. as an absorbent of air, and of acidity, and also as an easy purgative. I know several persons who could never bear to take the common Magnesia, with whom the calcined perfectly agrees. It seems likely to be very serviceable in flatulent cholics, and I have been informed of one very obstinate chronical case of that kind, which was greatly relieved, though not perfectly cured by the use of it in theChester Infirmary, under the direction of a very judicious and ingenious physician.
Even in gouty habits, joined with some warm aromatic, it may probably be found useful in correcting the very great flatulency which so much afflicts persons of this constitution; and perhaps the Cayenne pepper would be the most proper addition to it, on account of the small quantity of this spice that would be necessary to make the Magnesia gratefully warm to the stomach.
It will appear in the succeeding chapter that calcined Magnesia is strongly antiseptic: but I shall postpone my observations on that subject till I have related the experiments which prove its claim to that property.
On the action of various absorbents as promoting or retarding putrefaction.
The whimsical and ill-grounded hypotheses which were framed by the chymists of the sixteenth century, had, unhappily, too much influence, on the medical practice of that and the succeeding age. Among other false theories which the physicians had adopted from them, was that of attributing the origin of most diseases either to an acid or alkaline cause: but the former, being more obvious to the senses, was supposed to be the most frequent parent of diseases. Among others, fevers, even of the putrid kind, were imagined to be occasioned by an acid, and from hence the testaceous medicines acquired so high a degree of reputation, as to be deemed the grand correctors of acrimony, and were almost universally prescribed as alexipharmics; and the most celebrated compositions which are ranged under that head, contain a large proportion of these powders.
But a very learned physician, by a series of accurate and ingenious experiments on septics and antiseptics, has proved that chalk and all the testaceous powders accelerate the corruption of animalflesh, and from the result of one he made on bile with crab's eyes, he naturally concluded that all these substances would produce the same effect on that humour, as they had all uniformly proved septic to flesh. Yet, even upon this supposition, he candidly allows, that in some fevers, they may have their uses, even where no offending acid exists; as in order to cure some diseases, it may be requisite to attenuate the humours, and relax the fibres by a degree of putrefaction, and that possibly the crisis of fevers of this kind, may be hastened or perfected by the testaceous powders. In diseases, however, where the disposition to putrescency is already too strong, all medicines, which in the smallest degree increase such tendency should bestudiously avoided; and, on this account, the administration of the testacea in putrid, malignant fevers has of late been condemned by some ingenious writers. I was myself fully convinced of the rectitude of this opinion, and, in drawing up an account of the medicinal uses of Magnesia, had therefore suggested the impropriety of prescribing them where a bilious acrimony prevails. But not being able to recollect, that the septic powers of Magnesia had ever been experimentally proved,[r]I thought it would be most satisfactory to determine them by that method; little doubting butthat the event would justify my doctrine. My inquiries evince the accuracy with which Sir John Pringle has made his experiments, but as I was induced to carry the investigation of this subject further than he has proceeded, very different practical inferences, from those I at first expected, may, perhaps, be deduced therefrom.
EXPERIMENT II.
Two drachms of fresh beef, two scruples of Magnesia, and two ounces of distilled water were mixed in one bottle; and in another the same quantity of beef with two ounces of distilled water only: the meat was cut small, and the bottles were placed uncorked in a heat rather inferior to that of the human blood. Intwenty four hours the beef in the mixture with Magnesia was become quite putrid. The standard was perfectly sweet, and remained for some days, before it acquired the true putrid fœtor.
Being thus convinced that Magnesia is possessed of the property of hastening the putrefaction of animal flesh, in common with the rest of the absorbent tribe, it was imagined, that it might be of some consequence to practice, to determine how far it exceeded or was inferiour to the calcareous and testaceous earths as a septic; and also whether calcination produced any difference in it, in this respect. In reciting the experiments, where I only mentionMagnesia, I always would be understood to mean that powder in its uncalcined state, the calcined shall constantly be distinguished by that epithet. It also appeared to be a convenient opportunity of repeating the inquiry, how far the addition of the testacea might take effect in diminishing the antiseptic qualities of the contrayerva root.
EXPERIMENT III.
Into one phial were put two scruples of Magnesia, into a second the same weight of calcined Magnesia, and into three others the same quantity of chalk,pulv. e chel. cancr. comp.andpulv. contrayerv. comp.To each of these, two drachms of fresh beef, and two ounces of distilled water were added. A sixth phial was kept as a standard, and contained only the same proportions of beefand water. The bottles, distinguished in the order they are mentioned by the numbers 1, 2, 3, 4, 5, and 6, were placed in the same heat as that to which the Magnesia was exposed in the former experiment, and were frequently shaken up and examined.
In twelve hours, number 1 began to smell; an intestine motion was perceptible in numbers 3, 4, 5, and 6, but especially in the chalk. In twenty-four hours, number 1 was become highly putrid, number 3 smelled offensively, number 4 had acquired a very slight fœtor, as had number 5 which fermented briskly. The standard had acquired a vinous smell, but number 2 remained unchanged.
In thirty six hours, number 3 was very putrid, numbers 4 and 5had made little progress since the last examination, though number 5 was rather more putrid than the other, allowance being made for the peculiar odour of the contrayerva; but in four hours more they both stunk intolerably. The standard continued two or three days longer before it became absolutely putrid, and the calcined Magnesia preserved the beef untainted for several days longer, when it was removed to make room for other phials. The water which was mixed with the calcined Magnesia differed from all the others in not becoming bloody, nor did the beef in it seem so tender as when infused in lime water.
When I made the first experiment, I had not observed any discharge of air from the Magnesia and beef, and in the present oneno fermentation was perceptible either in number 1 or 2. As this was an unexpected circumstance in the former, I repeated the experiment several times, but the event was always the same.
Magnesia was afterwards compared with crab's eyes, burnt hartshorn, and prepared coral. The mixture with Magnesia grew putrid first, afterwards that with the crab's eyes; the other two remained for some hours longer before the putrid fœtor came on.
From the above experiments it appears that Magnesia Alba, when replete with fixed air, is a stronger septic to animal flesh than any other absorbent which was compared with it; and yet when deprived of its air by calcination, it powerfully resists putrefaction.Dr. Macbride has endeavoured to account for this difference between calcareous earths and quick-lime, by supposing the particles of the lime to insinuate themselves intimately into the texture of the beef, and to prevent the escape of the fixed air, by attracting, absorbing, and thus confining it within the substance of the beef. How far this theory is satisfactory is not my province to determine; and the matter is so obscure, that I do not presume to offer any conjecture of my own, relative to the reason of it.
Nitre is found to be a strong antiseptic when applied to animal flesh, but to resist the putrefaction of bile with a very disproportionate force: and Dr. Percival has lately observed the same difference in the action of the Columbo root.These variations encouraged me to try the effect of Magnesia on gall; but being strongly prepossessed with the notion of its septic quality, I entertained very small hopes of a different event. I was also desirous to compare the action of the calcined Magnesia with the other. The heat used in the succeeding experiments was the same as that in the preceding trials.
EXPERIMENT IV.
To two drachms of fresh ox gall, were added two scruples of Magnesia, and two ounces of water, in one phial. Two scruples of calcined Magnesia with the same quantity of gall and water were placed in another; and a third containing two drachms ofbile without any other addition than water, served as a standard, which began to have a rank smell in forty-eight hours, and in sixty hours was highly offensive. The calcined Magnesia and bile emitted a sweetish smell, something resembling that of the urine in a diabetes: the liquor which swam above was quite pellucid and colourless, whereas that of the other Magnesia was turbid and tinged green with the bile. Both were perfectly free from any putrid fœtor; the latter continued so for ten days, and the bile with the calcined Magnesia remained unchanged as long as any notice was taken of it.
EXPERIMENT V.
Twenty grains of Magnesiapreserved six drachms of ox's gall free from any signs of corruption for twenty-four hours after the standard containing gall and water, of each six drachms, had become putrid. A scruple of the calcined Magnesia mixed with the same proportions of gall and water, remained without any alteration as long as they were attended to, which was about ten days.
EXPERIMENT VI.
The putrid liquor which had been used as a standard in the fourth experiment, was divided into four parts, one of which was continued as a standard, to another was added about half a drachm of Magnesia, and an effervescence was procured by some drops of oil of vitriol. The offensive smell continued for a few minutes, but was soon much abated, and at length entirely sweetened. To another portion was added twenty grains of Magnesia only, this in fifteen minutes had almost lost its putrid smell, and in two or three hours became quite sweet. To the fourth was added the same weight of calcined Magnesia, which almost instantly deprived the liquor of every degree of putridity. The standard was then mixed with a scruple of crab's eyes, which, for about a minute, seemed to diminish the fœtor, but it then returned as strongly as ever; whereas the others continued sweet for several days.
EXPERIMENT VII.
Two drachms of putrid bile,which had been kept closely corked in a phial since the year 1770, and smelled very offensively, were mixed in a cup with twenty grains of Magnesia, and half an ounce of water, and thereby restored to sweetness. Twenty grains of calcined Magnesia were also added to two drachms of the same bile: on stirring them a pungent smell was observed, like that of volatile salts, and half an ounce of water being put to the mixture, the bile was totally deprived of any putrid smell. Even five grains of the same powder sweetened two drachms of putrid gall.
EXPERIMENT VIII.
Magnesia, calcined Magnesia, chalk, crab's eyes,pulv. e chel. cancr. c.andpulv. contrayerv.comp.each in the proportion of two scruples to two drachms of ox gall and two ounces of water, were exposed to the usual warmth. The crab's eyes mixture grew rank in twenty-four hours, and in forty-eight was absolutely putrid: the bile with the chalk was in the same condition in twelve hours more. The Magnesia mixture became putrid on the ninth day; thepulvis e chel.[s]on the tenth; but thepulvis contrayerv. comp.preserved the bile from corruption about three weeks, and no change was perceptible in that with the calcined Magnesia when examinedabove a month after their first admixture.
EXPERIMENT IX.
Twenty grains of Magnesia, and the same quantity of chalk, were separately neutralized with distilled vinegar, and their effects on ox gall compared with that of thirty grains of the artificial Epsom salt dissolved in a sufficient quantity of water. The bile in this solution became putrid in about sixty hours. That in the solutions made in the vegetable acid retained its sweetness for several days longer.
These experiments, which terminated so very differently from what I had expected, seem to justify, in some degree, the practice of giving the testaceous and absorbent medicines in fevers of a putrescent type, at the same time that they point out some of that class which ought to be avoided, and evince how fallacious a method it is to judge of the effects of medicinesa priori.
As the bile is, by many, supposed to be the great source of putrid diseases, ought not the antiseptics which may be prescribed in these cases, to be such as more particularly impede the corruption of this fluid, rather than that of flesh?
On account of the superiour antisepticity of the calcined Magnesia to most of the absorbents, and its greater purity and solubility, together with the probability of its acting as an evacuant, as well as a corrector of putrid bile, does it not appear to merit a preference to all other medicines of this class?
In diseases where an acid cacochymy prevails, and an alkalescent diet, such as wild fowl, fish, &c. is prescribed, but from the scarcity of these articles in some countries, cannot be complied with; may not taking Magnesia or the testaceous powders, immediately before or after meal time, coincide with this intention, by increasing the putrefactive fermentation of other animal food in the stomach, which in these disorders is almost totally subdued by the superabundant acid?
But where animal food is used in putrescent diseases, either through necessity, or the obstinacy of the patient, ought not Magnesia, in an uncalcined state, and all the calcareous and testaceous earths to be carefully abstained from?
Dr. Percival, in a volume of very ingenious experiments and observations which have been before referred to, has mentioned a physician of his acquaintance, who always observed his stools to be more particularly offensive after having taken Magnesia. Might not this proceed from the action of the Magnesia on the animal food he had eaten; and is it not reasonable to suppose that the effect might have been very different where a vegetable or milk diet had been used, as is generally the case in putrid fevers, and in young children?
I know a person whose stools are, in common, very little tinged with bile, who after taking calcined Magnesia, evacuates fæces of a very bilious appearance, though less fœtid than usual. It is a factworthy of observation, that in the experiments which were made with calcined Magnesia and bile, the latter was absorbed by, and had united with the former; and another remarkable circumstance was, that the watery part of all the mixtures which resisted putrefaction, acquired a very pungent, saline taste.