DANIEL RUTHERFORD'S INAUGURAL DISSERTATION

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DANIEL RUTHERFORD'S INAUGURAL DISSERTATION Communicated by LEONARD DOBBIN* Gavelton, Faladam, Blackshiels, Scotland

COMING from the same hand as the translation of Joseph Black's inaugural dissertation, printed in THIS JOURNAL in May and June, the trauslation of Daniel Rutherford's dissertatiun "On the Air Called Fired, or Mephitic," follows not imppropriately m a further notable record of the 18th century activity i n chemical innestigation in Scotland, which owed its existence i n no small measure to the initiative of Cullen. A s Black was a pupil of Cullen, so Rutherford was, in turn, a pupil of Black. It was from the latter that Ruth-

erford was led to the examination of atmospheric and other gases. His graduation thesis in medicine may hence be regarded as i n lineal descent from that of his master. It i s not necessary to enter here into any particulars concerning Rutherford, since a well-informed article by Dr. Mary Elwira Weeks, which appeared in THISJOURNAL in February, 1934, furnishes much interesting genealogical and other detail regarding him, and to this article the attention of readers i s directed.

ON THE AIR CALLED FIXED, OR MEPHITIC (CRUM BROWN'S TRANSLATION) AIR is the name generally given to that pellucid, thin, and mobile fluid in which we live, which surrounds us and all our belongings, and chiefly constitutes the atmosphere, in which, in fine, there float clouds and various exhalations from almost every thing on earth. The necessity of this air, both for animal life and for sustaining fire seems to have been noticed in all ages; but others of its properties, less obvious, have been detected in the last century, since Natural Philosophy began to be cultivated more accurately by means of experimentssuch are weight, elasticity, density, etc. As indeed air not only lies upon aff sublunary bodies, hut also, on account of its snhtilty insinuates itself into their internal structure, and lurks there intimately mixed with the other matter of which they are composed, recent Philosophers have wished to find out of what kind this air is, which, compacted in other things, animal, vegetable, or mineral, seems necessary to their constitution. Indeed they have thought it worth while to investigate whether it contracts any injury, either from rest or from contact with the bodies in which i t is inherent. And such inquiries do not seem useless, for such air fixed in other bodies, whenever it is given out, or, as they say, regenerated, differs so much from vital and wholesome air that it is often, not undeservedly called Mephitic. Its origin, then, and nature I shall endeavour as shortly as possible to explain, as I have learnt from my illustrious teachers

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* Formerly Reader in Chemistry, University of Edinburgh; Secretary of the Alembic Club, Chemistry Department. King's Buildings, Edinburgh.

Cullen and Black, to whom I owe nearly all I shall have to say on this subject. But not to extend this dissertation beyond the customary academic brevity, there is neither room for a description of the course of all the experiments I have made on this matter, nor would this he desirable; it will, I hope, sufficea t this time, to refer to their general results. By Mephitic Air, which some call Fixed Air, I understand, with the distinguished Prof. Black, that singular species of air which is fatal t o animals, which extinguishes fire and flame, and which is attracted with great avidity by quick-lime and alkaline salts. Air imbued with these properties seems to be produced in some places, in the very bowels of the earth, and sometimes to issue tbesce alone, as in the Averna of the ancients, and in the Grotta di Cani near Naples, sometimes to flow out, mixed with mineral waters, as in the Pyrmont spring. Further, it arises from the lungs of animals, for air, however wholesome to begin with, becomes to some extent mephitic by repeated respiration.* It is also produced by the action of fire, for pure air passed through burning bodies acquires thence the said malignity. Lastly it is produced by means of some chemical processes, especially when substances are resolved into their component parts, whether that takes place as an effect of heat or of some vehement internal motion, as * Dr. Black's Lectures.

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in vinous fermentation, or lastly by the action of any menstruum by which some constituents of the substance are violently tom from others, as when an acid is poured on chalk or limestone, and indeed it is in this way that it can best be prepared for experimental purposes. Mephitic air so produced, or as they say regenerated, is endowed with some singular properties in which it differs much from common air, and by which i t can easily be recognised. It greatly exceeds common air in specific gravity, in the proportion namely of 15l/~or 16 to 9. And hence it is that when i t spontaneously exhales from the earth i t scarcely rises more than a foot or two above the sur-

which it for a long time wards off putrefaction from other bodies with which i t is brought into contact or mixed; although I have not yet found it able to expel or counteract putrefaction already begun, or to restore putrid flesh, or liquids shut up with it, to their former purity. But the chief difference between oure air. or anv other species of air, and this mephitic air is to be found in that conspicuous sympathy and attraction with which i t unites with lime, with alkaline salts, and with any bodies of the same nature. It is caught in their embrace and joined in so stable a union that it, so to say, becomes solid with them, yet not without a great ~~

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face; hence also if a cylindrical vessel filled with it be inverted a little above a lighted candle, the air carried down by its own weight extinguishes the flame there;* but if common air is allowed access it is quickly attracted by it, and, its powers being diminished, loses its special character; hence it cannot be kept long in an open vessel however tall. It affects the nostrils and palate with a certain not unpleasant savour, not unlike that often given off by new and still fermenting beer. It changes the colour of infusion of violets from blue to purple, which pure air by no means does. Further, i t exerts an eminent antiseptic power, by

* Dr. Black's Lectures.

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change in their nature. And as the preparation of lime sefves in no small degree for the explanation of many phenomena connected with the matter in hand, it will be worth while to consider how any calcareous substance, for instance, chalk, is converted into lime, and what new properties it acquires. Chalk, then, as i t is dug out of the earth is a mi!d substance, almost tasteless, free from all acrimony; it quietly admits the access of water, without any movement or noise, yet it does not dissolve in it, but dissolves easily in an acid liquid, not indeed without brisk conflict and effervescence; i t produces no change on alkaline salts. nor thev on it. But if chalk is subjected to a vehement heat, or, as

the Chemists say, is calcined, it then undergoes a wonderful change, and is converted into the said lime. For lime, so prepared, is distinguished from chalk by various properties. It is, namely, much lighter and more brittle; it has acquired a truly caustic acrimony; when water is poured on it, if it has been recently prepared, i t becomes hot, hisses, swells, and cracks, and then dissolves in it; it imbues alkaline salts with its burning acrimony; lastly i t is strongly absorbed by acids; hut, strange to say, unites with them now quietly and without any violent motion or ebullition. To explain these surprising changes, Chemists and Philosophers formerly devised various hypotheses, but all vain and inept, till a t length our distinguished Professor of Chemistry, Dr. Black solved the difficulty, not by making any theory, but by means of very ingenious and trustworthy experiments.* For, having very accurately examined the nature of chalk and of lime, he found that the one can be changed into the other, and that all such changes depend solely on the expulsion or the restoration of air, that in fact chalk deprived of air becomes lime, and lime, on the reabsorption of air is brought back to the nature of chalk. For he found that chalk is filled with a vast quantity of mephitic air, and that, if pure and dry, it contains nothing else that is volatile, and so when i t is strongly heated it loses nothing of its substance except air; for the earth can endure the greatest heat with impunity. If a drachm of chalk requires a given quantity of acid for its complete solution, that which remains of another drachm of the same chalk after it has been subjected to fire will not be perfectly dissolved unless we add the same quantity of acid. Moreover i t is most worthy of notice that the chalk by solution in acid loses exactly the same weight as by calcination in the fire.+ And the lime takes up from the fire no saline, above all no acrid particles, for it is wholly soluble in water, and by every test is found to he homogeneous.X If mephitic air is exposed to lime, it is a t once absorbed, and the earth recovers its former weight and character.** So if we introduce such air into limewater, it immediately becomes turbid, and soon deposits an earthy powder, in no way to be distinguished from pure chalk. By an experiment of this kind it is possible to ascertain with certainty whether a given air contains even a trace of mephitic air. Similarly lime when mixed with a solution of an alkaline salt, which abounds in mephitic air, becomes mild by taking up this air; while the salt, deprived of its air, becomes caustic alkali. In quite the same way lime by long exposure to free air becomes mild and loses its peculiar qualities by absorption of the mephitic air which happens to he there. Acids, when they dissolve chalk, expel the air; so that if the earth is precipitated from this solution,

* Edin. Phys. Obsem., Val. 2 , pp. 157ff t Ibid., Vol. 2, P. 194. ? I W . , p. 194. ** Ibid., p. 195.

without air being supplied, i t takes the form of lime, as happens when caustic alkali is added to it.* All calcareous stones agree in this, that by exposure to a sufficientheat they can be converted into a similar lime; yet they differas to the quantity of air contained in them; for the harder they are, the less air do they seem to have, the softer the more. So very hard black marble loses in the fire about a/7 of its weight, the softer white marble %, calcareous spar '/n, and chalk nearly the half. As mephitic air is attracted by chalk, so is it also by Magnesia alba, another species of absorbent earth. But here the properties are less changed by the addition; for, whether free from air or saturated with it, i t remains insipid and insoluble in water; nor does any great difference arise from this, except that the one unites quietly with acids, the other with effervescence. Magnesia, properly prepared, seems to consist to the extent of '/= of air.7 Quite similar is the mutual attraction between this air and alkaline salts. For these, when deprived of it, become more a a i d and greedier of water, so much so that fixed alkali can only with difficulty, volatile alkali not a t all, be brought into the solid form. On the contrary, when saturated with air they very easily form solid crystals;$ both are then full of a great quantity of air, namely the fixed about 6/12, and the volatile '/=. Hence i t happens that there often arises a slight eEemescence when we precipitate calcareous earth from an acid by means of a mild alkali; for the earth is unable to absorb the whole of the air.** But yet mephitic air by no means unites with the bodies just mentioned without discrimination, for certain of them it prefers, and leaves some to unite with others, and this in the following order, above all it prefers lime, then fixed alkali, after that Magnesia alba, and lastly volatile alkali.tt From these things many chemical processes and phenomena resulting from them can be easily explained. So far the union of mepditic air with alkaline salts and calcareous earths, of which i t seems to he very fond, has been spoken of, but i t also either spontaneously unites with some liquids, or, a t all events can he combined with them, and first with water.*** For if i t is introduced into a vessel full of water by means of a tube the end of which reaches to the bottom of the vessel, as it rises up it sets the water into a kind of boiling motion; hut i t does not all escape, for no small part of it remains with the water, and is, so to say, dissolved in it. The quantity of air so dissolved varies; for the lighter or warmer the atmosphere, so much the less of the injected air is retained by the water; yet in general the volume of the air, when again recovered

* Edin. Phys. Observ., Val. 2, p. 206.

t Ibid., Val. 2, p. 172.

$ Dr. Black's Lectures. ** The noble and ingenious Mr. Cavendish was the first to observe these and many other things about mephitic air. Phil. Trans.,1766 and 1767. tt Edin. Phys. Obsew., p. 224. *** Cavendish, loc. cit.

from the water, usually exceeds by a little the volume of the water. Water impregnated with this air acquires an acidulous, somewhat spirituous, and not unpleasant taste, and in some other of its properties emulates the nature of an acid. For many bodies now dissolve in it, which cannot be dissolved by plain water. For instance Magnesia alba and calcareous earths.* And from this i t may be understood why mephitic air, driven into lime-water, a t first separates the earth, which soon disappears, being again absorbed and almost completely dissolved. Many metals are also to some extent dissolved by water charged with that air, especially iron and zinc;t and thence the water acquires the taste and other less obvious qualities of the dissolved metal, even if the proportion of metal is very small; thus iron dissolved in such water gives a black colour with galls. And so it seems likely that water so impregnated, should, while washing against metallic veins and mineral strata in the bowels of the earth, carty away with it parts of them, and on bursting forth from the earth be enriched with varied metallic efficacy. Hence it comes that, for the most part, these waters convert bodies placed in them as i t were into stone; and hence also that water is obtained from some springs and wells, which, because of the calcareous earth dissolved in it, is unsuitable for domestic and culinary use till i t has been purified by boiling or subsidence.! It is therefore not surprising, if scarcely a single grain of solid vitriol can be pr6pared from cbalybeate waters, although by boiling, iron is deposited in the form of ochre; because by the heat the menstruum by which the metallic parts were dissolved in the water has been driven off. As far then as the virtues of mineral waters depend on that air, it will not be difficult to imitate them by art. That air resident in waters is often so volatile and fugacious that i t quickly flies away if any access of external air is allowed; and whatever had been dissolved in it is separated as a pellicle, or if it should be heavier, goes down to the bottom. 'And so water of this sort should be kept in well corked and inverted bottles. And that air can not only be dispelled by the access of external air or by beat, but can also be extracted by the air-pump, and be set free, although slowly, by the addition of salts. Mephitic air is also absorbed by other liquids, such as spirit of wine, expressed oils, etc.r But as their obvious properties do not seem to be much changed by this. I have nothing. " to sav about them. Leaving now the mephitic air which is obtained from calcareous bodies, I shall add a few words as to such air of other origin; and first of that which is rendered malign by animal respiration. It seems indeed surprising that, although no animals can live without the help of atmospheric air, yet this, by vital action becomes so deadly, that i t destroys life more quickly

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* Cavendish, bc. cit. t Lane, Phil. Trans.. 1769. $ Cavendish, loc. cit.

than almost any other poison. For the most lively animals immersed in this gas cease to live in almost a moment of time. Nay, if almost any animal is shut up in a glass vessel, without any communication with the external air, it begins to be affected with a certain trouble and restlessness, and sooner or later, according to the capacity of the vessel and the volume of the air in which it breathes, dies, as if struck with apoplexy. In the meantime the air in which the animal is, although i t may seem a t first to be a little expanded and rarified by its heat, yet i t soon begins to lose somewhat of its elasticity, until when the animal is dead, it gradually returns to its original volume, and then is brought into narrower limits, and is found to be to some extent mephitic. Thus the air in which a mouse had died had lost about of its volume; and about of i t was absorbed by alkali; the flame of a wax candle immersed in it was a t once extinguished, but the wick remained ignited a little longer. It seems very probable that different animals, breathing in some fixed quantity of air, will render a different proportion of it malignant; nay, that the same animal on different occasions, will be able, more quickly or more slowly, to infect the air with that lethal quality; especially as experience shows that the volume of the air, in which different animals are shut up is now more, now less diminished, sometimes namely part of the whole, sometimes not more than part. Moreover i t is known from experiments that among animals of the same species some can bear the malignant air longer than others; for if two mice are shut up in the same air, one often lives longer than the other; and it is indeed likely that the same might happen to the same animal a t different times. These things make it difficult to determine the proportion of mephiti6 air, by which common air is made unfit for respiration; yet perhaps that would result if it contained '/s part, or '/a of mephitic air. But, by the respiration of animals, wholesome and good air not only becomes in part mephitic, but i t also suffers another singular change. For, after a11 the mephitic air has been separated and removed from i t by means of caustic lye, still what remains does not become in any way more wholesome; for although it produces no precipitate in lime-water, it extinguishes both flame and life no less than before.- Nay, it is doubtful whether mephitic air is actually generated in the lungs, or, as seems more probable is perhaps already formed in the body from the food, and ejected by the lungs, as something noxious. It is, namely, observed that the warmer animals are, the more perfect and constant is their respiration, and the more quickly do they infect the air with a malignant nature; may we not then suspect that animal heat and that alteration of the air arise from the same cause?** As the life of animals depends on the free use of air, so this is altogether necessary for the support of flame

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** Prof. Black.

and fire. But no less by fire than by respiration is i t so changed as to be unfit for either use and contrary to both. And as the effects are nearly the same, what I have brought forward as to respiration may be repeated as to combustion. Some bodies when burnt make air malignant more easily than others; thus phosphorus from urine will continue to shine in air in which a wax candle has been extinguished. Air which has just supported lire loses scarcely less of its elasticity than by animal respiration; its volume, namely, is diminished by about a twentieth part. But if nitre has been mixed with the burning body, the volume is rather increased, namely by the addition of the air which before lay hid in the nitre, and is now expelled by the fire. The amount of mephitic air from a' candle enclosed in a glass has about the same ratio to the whole quantity of air enclosed, as if an animal had died in it. Also about the same proportion of mephitic air mixed with common air seems to suffice to extinguish flame and life. Air which has been blown by bellows through ignited coals, and then purified from all mephitic air, is, nevertheless still found to be malignant and quite similar to that which is spoiled by respiration. Nay, it is evident from experiments that this is the only change of the air that can be ascribed to combustion. For if any material whatever, consisting of phlogiston and'a simple fixed base, is set on fire, the air thus produced seems to contain no trace of mephitic air. Thus air in which sulphur or phosphorus from urine has been burned, although very malignant, does not precipitate lime from water. Sometimes indeed, if it has been from phosphorus, i t produces a cloud in lime-water, but very slight and not to be attributed to mephitic air, but rather to the acid which is contained in phosphorus, and which, as experiments have shown, has this singnlar property. From these things i t then follows that pure air cannot be converted into mephitic by combustion; but rather that that arisgs or is ejected from the body so decomposed. From these things we may also conclude that that malignant air is composed of atmospheric air united with phlogiston and, as i t were, saturated. And indeed, this is confirmed by the fact that air which has just served for the calcination of metals, and has taken phlogiston from them, is obviously of the same kind. The last species of mephitic air which I shall mention is that which is produced by the decompositionof bodies: And a t first sight i t would seem that a great quantity arises in this way; seeing that there is rarely a chemical process without the eruption of a great deal of elastic air. That excellent man and accomplished philosopher, Hales, has found this to such an extent confirmed by experiments, that he would seem to have got a suspicion from them that that air played the part of a bond for uniting the elements of all bodies. From his tifne, and especially from the discoveries of (Cl.) Black, some authors have indeed, not only

adopted this opinion, but have besides this, concluded that real mephitic air, such as is absorbed by alkalis, is the universal bond of the elements, from the departure or separation of which they would deduce the breaking up of substances; nay, they reason thus even on medical matters, and would seek thence the causes of many diseases, and the powers of remedies. But although there are, perhaps, not lacking arguments to support Hales' doctrine, as far as it supposes that the cohesion of bodies depends on some elastic fluid, yet certainly there is no experimental proof that meph~tlcair performs such a function. By similar reasoning i t might be maintained that this was done by acid, alkali, oil, or anything else that is a frequent product of chemical analysis. Passing by many observations by which the singular nature of mephitic air is beginning to be elucidated, and which are altogether opposed to this hypothesis, it is moreover to be noted, that that air is in no case produced from bodies in such quantity as it supposes. For, except fermenting vegetables which sometimes indeed pour it out abundantly, i t does not seem, in hardly any other case, to be produced in sufficient plenty. And when the air, so often generated or expelled from bodies by chemical art, as in Hales' experiments, upon which this hypothesis specially relies, is examined, it is found that it often contains no mephiticair, and that in all cases by far the greater part of i t has a quite opposite nature. Thus the elastic vapour which arises from metals when they are acted on by acids has hardly any of the properties of mephitic air; it varies according as i t is produced from metals more, as it were, saturated with phlogiston, or according as it-is more or less infected by the fumes of the acid: For sometimes i t is found to be inflammable, and sometimes it extinguishes flame; yet of whatever kind it be, it is not attracted by alkalis. What, again, is given off in the conflict of acids with oils does not differ much from, that which comes from metals, except that i t has a w r y little mephitic air mixed with it; from them (oils) indeed, vitriolic acid extricates an inflammable vapour, nitrous acid one that extinguishes flame. By the action of heat, an elastic air is also obtained from animal and vegetable substances and from bituminous minerals, wbich always flashes and takes fire on the application of a flame; though a small proportion of i t seems to consist of mephitic air. But what is given off from other mineral bodies wbich I have subjected to experiment, such as sea-salt, nitre, etc., if distilled in glass or in earthen vessels, scarcely differs from common air. Lastly, air which arises from putrefying flesh similarly takes fire,* and is also found to be, in part, mephitic. But surely the putrefaction of flesh can no more be attributed to the seliaration of this, than can the combustion of coal. Indeed very many of the phenomena of putrefaction simulate so much a very gentle combustion, that it would seem probable that both de-

* Cavendish, lac. cit.

pend on the same cause variously modified; namely the varying agitation of the phlogiston, as it escapes from the substance and is dissipated into vapours. And to this indeed points the fact that air in which flesh has become putrid is in part converted into mephitic air, and in part into that other species, as in combustion. I intended to add some things as to the composition of mephitic air, and thence to seek a.way by which its malignity could be destroyed; but as to this I have hitherto found nothing certain. Some observations point to the view that this air is composed of phlogistic matter and atmospheric air; for i t is never produced but from bodies abounding in matters fit for combus-

tion; phlogiston also seems to participate with other bodies, and hence is able to reduce the cakes of metals. I say of phlogistic matter,because, as noted above, pure phlogiston united to common air seems to form another species of air. Lately, as I have heard, the very ingenious Joseph Priestly [sic], author of the famous history of electricity, has made it very probable that vegetables growing in mephitic air dispel, or as it were extract from it the noxious properties, and restore i t to its pristine salubrity; and also that mephitic air, by the addition of air from putrid flesh, in part loses its malignity. But the experiments by which these things might be confirmed have not as yet been made with sufficient accuracy.