Chapter 2

The experiments seem to prove that the transference of phlogiston to the air does not always diminish its bulk, which, however, the experiments mentioned in Sec.Sec. 8.16 shew distinctly. But the following will shew that that portion of the air which unites with the inflammable substance, and is at the same time absorbed by it, is replaced by the newly formed aerial acid.

+22. Sixth Experiment.+--After the fire had gone out and everything had become cold in the experiments mentioned above (Sec. 21. _a._ _b._ _c._), I poured into each flask 6 ounces of milk of lime (lime water which has in it more unslaked lime than the water can dissolve); I then placed my hand firmly on the mouth of the flask and swung it several times up and down; then I held the flask inverted under water and drew my hand a little to one side, so that a small orifice might be made. Water immediately rose into the flask. Then I shut the mouth again very tightly with my hand under water, and afterwards shook it several times up and down. I opened it again under water; this operation I repeated twice more until no more water would rise into the flask, or until no more aerial acid was present in it. I then perceived that in each experiment between 7 and 8 ounces of water rose into the flasks, consequently the nineteenth part of the air has been lost. This was indeed something, but since in the combustion of phosphorus (Sec. 17) nearly the third part of the air was lost, there must be another reason besides, why as much is not absorbed in this case also. It is known that one part of aerial acid mixed with 10 parts of ordinary air extinguishes fire; and there are here in addition, expanded by the heat of the flame and surrounding the latter, the watery vapours produced by the destruction of these oily substances. It is these two elastic fluids, separating themselves from such a flame, which present no small hindrance to the fire which would otherwise certainly burn much longer, especially since there is here no current of air by means of which they can be driven away from the flame. When the aerial acid is separated from this air by milk of lime, then a candle can burn in it again, although only for a very short time.

+23. Seventh Experiment.+--I placed upon the stand (Sec. 21. _b._) a small crucible which was filled with sulphur; I set fire to it and placed the flask over it. After the sulphur was extinguished and everything had become cold, I found that out of 160 parts of air, 2 parts were driven out of the flask by the heat of the flame. I next poured 6 ounces of clear lime water into the flask and dealt with it by shaking, as already explained, and observed that the sixth part of all the air had been lost in consequence of the combustion. The lime water was not in the least precipitated in this case, an indication that sulphur gives out no aerial acid during its combustion, but another substance somewhat resembling air; this is the volatile acid of sulphur, which occupies again the empty space produced by the union of the inflammable substance with air. It is not, as may be seen, a trifling circumstance that phlogiston, whether it separates itself from substances and enters into union with air, with or without a fiery motion, still in every case diminishes the air so considerably in its external bulk.

+24. Experiments which prove that ordinary air, consisting of two kinds of elastic fluids, can be compounded again after these have been separated from each other by means of phlogiston.+

I have already stated in Sec. 16 that I was not able to find again the lost air. One might indeed object, that the lost air still remains in the residual air which can no more unite with phlogiston; for, since I have found that it is lighter than ordinary air, it might be believed that the phlogiston united with this air makes it lighter, as appears to be known already from other experiments. But since phlogiston is a substance, which always presupposes some weight, I much doubt whether such hypothesis has any foundation....

+25.+ How often must not chemists have distilled the fuming acid of nitre from oil of vitriol and nitre, when it is impossible that they should not have observed how this acid went over red in the beginning, white and colourless in the middle of the distillation, but at the end red again; and indeed so dark-red that one could not see through the receiver? It is to be noticed here that if the heat is permitted to increase too much at the end of the distillation, the whole mixture enters into such frothing that everything goes over into the receiver; and, what is of the greatest importance, a kind of air goes over during this frothing which deserves no small attention. If one takes for such distillation a very black oil of vitriol, not only does the acid go over at the beginning of a far darker red than when one takes a white oil of vitriol, but further, when one introduces a burning candle into the receiver after about an ounce has gone over, this goes out immediately. On the other hand, when one places a burning candle in the receiver filled with blood-red vapours, towards the end of the distillation when, as has been said, the mixture froths strongly, not only will it continue to burn, but this will take place with a much brighter light than in ordinary air. The same thing occurs when one attaches, at the close of the distillation, a receiver which is filled with an air in which fire will not burn, for, when this has been attached for half an hour, a candle will likewise continue to burn in the air.

In this case there now arises in the first place the question: Are the vapours of the acid of nitre naturally red? I beg leave to raise this question here because I believe there are people who advance the redness of this acid as a distinguishing characteristic. The colours of the acid of nitre are accidental. When a few ounces of fuming acid of nitre are distilled by a very gentle heat, the yellow separates itself from it and goes into the receiver, and the residuum in the retort becomes white and colourless like water. This acid has all the chief properties of acid of nitre, except that the yellow colour is wanting. This I call the pure acid of nitre; as soon, however, as it comes into contact with an inflammable substance, it becomes more or less red. This red acid is more volatile than the pure, hence heat alone can separate them from one another; and, for exactly the same reason, the volatile spirit must go over first in the distillation of Glauber's spirit of nitre. When this has gone over, the colourless acid follows; but why does the acid make its appearance again so blood-red at the end of the distillation? Why has not this redness already been driven over at the beginning? Where does it now obtain its phlogiston? This is the difficulty.

+26.+ I intimated in the preceding paragraph that the candle went out in the receiver at the beginning of the distillation. The reason is to be found in the experiment which I have cited in Sec. 13. In this case the acid of nitre, passing over in vapours, takes to itself the inflammable substance, whose presence is indicated by the black colour of the oil of vitriol; as soon as this has taken place it meets with the air, which again robs the now phlogisticated acid of its inflammable substance; by this means a part of the air contained in the receiver becomes lost, hence the fire introduced into it must go out (Sec. 15).

+27.+ The acid of nitre can attract phlogiston in varying quantity, when it likewise receives other properties with each proportion. (_a._) When it becomes, as it were, saturated with it, a true fire arises, and it is then completely destroyed. (_b._) When the inflammable principle is present in smaller quantity, this acid is converted into a kind of air which will not unite either with the alkalies or with the absorbent earths, and with water only in very small quantity. When this acid of nitre, resembling air, meets with the air, the latter takes the inflammable substance from it again, it loses its elasticity (Sec. 13), the vapours acquire redness, and the air undergoes at the same time this no less remarkable than natural alteration, that it is not only diminished, but also becomes warm. (_c._) When the acid of nitre receives still somewhat less phlogiston, it is likewise converted into a kind of air, which, like the air, is also invisible, but unites with the alkalies and earths, and along with them can bring forth real intermediate salts. This phlogisticated acid is, however, so loosely united with these absorbing substances, that even the simple mixture with the vegetable acids can drive it out. It is present in this condition in nitre which has been made red hot, and also in _Nitrum Antimoniatum_. When this acid of nitre meets the air it also loses its elasticity and is converted into red vapours. When it is mixed in a certain quantity with water, this acquires a blue, green, or yellow colour. (_d._) When the pure acid of nitre receives but very little of the inflammable substance, the vapours only acquire a red colour, and are wanting in expansive power; it is, however, more volatile than the pure acid. This acid holds this small quantity of phlogiston so firmly that even the air, which so strongly attracts the inflammable substance, is not able to separate this from it.

* * * * *

+29.+ I took a glass retort which was capable of holding 8 ounces of water, and distilled fuming acid of nitre according to the usual method. In the beginning the acid went over red, then it became colourless, and finally all became red again; as soon as I perceived the latter, I took away the receiver and tied on a bladder, emptied of air, into which I poured some thick milk of lime (Sec. 22) in order to prevent the corrosion of the bladder. I then proceeded with the distillation. The bladder began to expand gradually. After this I permitted everything to cool, and tied up the bladder. Lastly I removed it from the neck of the retort. I filled a bottle, which contained 10 ounces of water, with this gas (Sec. 30, _e._), I then placed a small lighted candle in it; scarcely had this been done when the candle began to burn with a large flame, whereby it gave out such a bright light that it was sufficient to dazzle the eyes. I mixed one part of this air with three parts of that kind of air in which fire would not burn; I had here an air which was like the ordinary air in every respect. Since this air is necessarily required for the origination of fire, and makes up about the third part of our common air, I shall call it after this, for the sake of shortness, Fire-air; but the other air which is not in the least serviceable for the fiery phenomenon, and makes up about two-thirds of our air, I shall designate after this with the name already known, of Vitiated Air.

+30.+ Anyone might ask me in what way I bring air from one vessel into another. I find it necessary therefore to describe this in the first place. My arrangements and vessels are the very simplest that one can possibly have: flasks, retorts, bottles, glasses, and ox bladders are the things which I employ. The bladders, while they are still fresh, are rubbed, and blown up very fully, then tightly tied and hung up to dry. When I wish to use such a bladder and find it blown up just as fully as at first, I am thereby assured that it is tight.

(_a._) When I wish to collect any kind of air in a bladder, for example the phlogisticated acid of nitre (Sec. 13), I take a soft bladder smeared inside with a few drops of oil, and place in it some filings of a metal, as iron, zinc, or tin; I then press the air as completely as possible out of the bladder and tie it very tightly over a small bottle into which some _aqua fortis_ has been poured; I then partly unfold the bladder so that a few iron filings may fall into the _aqua fortis_, according as this dissolves the bladder becomes expanded. When I have collected enough of the air so produced, I tightly tie up the bladder with a thread close above the mouth of the bottle, and then detach it from the bottle. (_b._) If this phlogisticated acid of nitre is mixed with aerial acid, which is the case when the acid of the nitre is extracted over sugar, I tie a bladder, softened with some water, to the extreme end of the neck of the retort A (Fig. 3); in order, however, that I may properly prevent the escape of the air it is necessary to scratch the neck of the retort somewhat at this place with a flint. (Retorts which I employ for investigations of this kind I have blown not larger than to be capable of holding only from one half to three ounces of water, but which have at the same time a neck which is about half an ell long, and that for this reason that the attached bladder may not be destroyed during the operation by the heat of the furnace or by the hot vapours.) Into this bladder I pour some milk of lime (Sec. 22), and press the air out as fully as possible. This lime will absorb the aerial acid during the distillation, and leave the phlogisticated acid of nitre untouched. (_c._) In exactly the same way as is described in _a_ I also collect aerial acid and the inflammable air of sulphur (of which I shall speak further on). But if the bladders are moist, or even if only the air surrounding them is so, both these kinds of air penetrate completely through the bladders in a few days; if the bladders and air are dry, however, this does not take place. I obtain inflammable air from the metals, as iron or zinc, in exactly the same way, except that I place the bottle in warm sand. This air is still more subtle than the preceding; it penetrates through the fine pores of the bladder in a few days, although air and bladder are dry. I frequently experienced this to my vexation. (_d._) I not infrequently catch air in bladders, without any bottles. I place in a soft bladder (AA, Fig. 4) the material from which I intend to collect the air, for example, chalk; above this chalk I draw the bladder together with twine BB; I then pour above it the acid diluted with water and press out the air as completely as possible; I finally tie up the bladder above at CC. I then untie the twine B, when the acid runs upon the chalk; it immediately drives out the aerial acid, whereupon the bladder must expand. (_e._) When I require to get an air out of the bladder into a flask, glass, retort, or bottle, I fill such apparatus with water and place in it a tightly fitting cork; I then tie the bladder which contains the air, that is, the opening from C to D (Fig. 4), very firmly over such bottle; I then invert the bottle so that the bladder comes below and the bottle above, whereupon I hold the bottle with the left hand and with the right I withdraw the cork; I hold this cork firmly between both fingers inside the bladder until the water has flowed out of the bottle into the bladder, and the air has mounted out of the bladder into the bottle; I then put in the cork and detach the bladder from the bottle. When I wish to preserve the air for a long time I place the neck of the bottle in a vessel with water. (_f._) When there is aerial acid in the bladder, or another air which can unite with water, and I wish to unite it with water neatly, I fill a bottle with cold water, and, after it has been attached to the bladder, I permit about the fourth part to run into the bladder; I then push the cork, which, as previously, was firmly held within the bladder, into the bottle again; I then shake the bottle gently, when the air will dissolve in the water. Thereupon I make a small opening by means of the cork, when air passes out of the bladder into the bottle in order to fill up again the space which has become empty, without any water running into the bladder; I then push the cork again into the bottle and shake the water contained in it. I repeat this operation two or three times more, when the water is saturated with this air. (_g._) When I wish to mix together two kinds of air in a flask or bottle, I permit in the first place just as much water, by measure, to run from the bottle filled with water, into the bladder, as I wish to have of air. I then tie the bottle over with a bladder filled with another kind of air and permit the remaining water to run into the bladder, whereupon I immediately replace the cork in the bottle, as soon as the last of the water has run out. (_h._) When I wish to have in a bladder an air collected in a bottle, I reverse the operation. That is to say, I fill the bladder with as much water as I wish to have in it of air and tie it up at the top; I then tie this bladder tightly over the top of the bottle and untie the ligature of the bladder, draw the cork out of the bottle and so permit the water to run out of the bladder into the bottle. I then tie up the bladder, which now contains the air out of the bottle, and detach it from the bottle. (_i._) When I have in a bottle an air mixed with another kind of air which can be absorbed by water or lime, but wish to know how much of each kind is present in the bottle, I tie over it a bladder into which so much milk of lime has been poured that the bottle can be filled with it; I then withdraw the cork and permit the water or milk of lime to run into the bottle. I afterwards invert the bottle and permit the milk of lime to flow again into the bladder; I repeat this running out and in several times. So much air by measure has been absorbed as there now remains behind of milk of lime in the bottle.

These are the methods which I employed in my investigations of air. I admit that they will not particularly please some, because they do not decide with great exactness. They afforded me satisfaction, however, in all my investigations; and people will often split a hair where it is not in the least necessary.

+31. Continuation of the Experiment mentioned in Sec. 29+ ...

Anyone might object and say that the air obtained according to Sec. 29 is perhaps nothing else than a dry acid of nitre converted into elastic vapours. But if this opinion had any foundation, this air should not only be corrosive, but should also produce nitre anew with alkalies. This, however, does not occur. Nevertheless, this objection would possess considerable weight were I not able to prove that several substances produce the same air as the acid of nitre does during distillation. But proof of this is not wanting.

I have proved in a treatise on manganese, which is to be found in the Transactions of the Royal Swedish Academy of Sciences for the year 1774, that this mineral is not soluble in any acid unless an inflammable substance be added, which communicates the phlogiston to the manganese, and by this means effects an entrance of the latter into the acids. I have shown in the same place that vitriolic acid, nevertheless, during a strong distillation with powdered manganese, unites with it and makes it soluble in water; and if this manganese is separated again from the vitriolic acid by means of precipitating agents, there are found in it the most distinct traces of the inflammable substance.... I had already observed a few years ago, that if in the calcination of manganese with oil of vitriol in an open crucible, some coal dust was driven by the current of air over the surface of this mixture, these fine coals took fire in the same instant with very great brilliancy. I accordingly made the following experiments.

+32. First Experiment.+--I mixed so much concentrated oil of vitriol with finely powdered manganese that it became a stiff magma. I distilled this mixture from a small retort on the open fire. In place of a receiver I made use of a bladder, empty of air, and, in order that the vapours which might pass over should not attack the bladder, I poured into it some milk of lime (Sec. 30, letter _b_). As soon as the bottom of the retort became red hot, an air passed over which gradually expanded the bladder. This air had all the properties of a pure fire-air.

+33. Second Experiment.+--When I distilled two parts of finely pulverised manganese with one part of the phosphorous acid of urine in the same way as is indicated in the preceding paragraph, I likewise obtained fire-air.

+34. Third Experiment.+--(_a._) I dissolved in _aqua fortis_ the white magnesia employed in medicine; I evaporated this solution to dryness. I then placed the salt in a small retort for distillation, as is described in Sec. 32. Even before the retort was red hot the acid of nitre separated from the magnesia, and that in blood-red vapours; and at the same moment the bladder began to expand. The air thus obtained was my fire-air.

It is thus seen constantly that the acid of nitre goes off again blood-red when separated by means of heat from the metals which had been dissolved in this menstruum.

(_b._) I distilled mercurial nitre in the foregoing manner until the acid of nitre had separated from the residual red precipitate. In this case also I obtained our fire-air.... Whence comes the boiling of nitre, fused in a crucible and obscurely red-hot? Neither smoke nor vapours are seen to rise from it, and yet coal dust flying above the open crucible takes fire, burning brilliantly. Whence comes it that such nitre maintained in red-hot fusion in a glass retort for half an hour, becomes moist in open air and deliquesces after cooling, and still does not show any trace of alkali? (Sec. 27, letter _c._) What is the reason that this liquefied nitre permits its volatile acid to escape immediately, when rubbed or mixed with the vegetable acids?... If the chemists of the preceding century had thought worthy of a more particular examination, the elastic fluids resembling air which manifest themselves in so many operations, how advanced should we now be! They desired to see everything in corporeal form, and to collect everything as drops in the receiver. This is now for the first time better inquired into, and the air has begun to be carefully examined: and who is there who does not perceive the advantage which the results of such experiments carry with them?

* * * * *

+35. Fourth Experiment.+--I put an ounce of purified nitre into a glass retort for distillation and made use of a bladder, moistened and emptied of air, in place of a receiver (Fig. 3). As soon as the nitre began to glow it also began to boil, and at the same time the bladder was expanded by the air that passed over. I proceeded with the distillation until the boiling in the retort ceased, and the nitre was about to force its way through the softened retort. I obtained in the bladder the pure fire-air which occupied the space of 50 ounces of water. This is the cheapest and best method of obtaining fire-air.

* * * * *

+38. Fifth Experiment.+--I took a silver solution prepared with acid of nitre, and precipitated it with alkali of tartar; I washed the precipitate thus obtained and dried it. I then placed this calx of silver in a small glass retort on the open fire for reduction, and fastened an empty bladder to the neck. The bladder was immediately expanded by the air which passed over. After the end of the distillation I found the calx of silver half melted together in the retort, with its metallic lustre; however, as I had effected the precipitation with alkali of tartar, and this is always united with a quantity of aerial acid which attaches itself to the calx of silver in the precipitation, so this acid was necessarily present also in the bladder. This acid was removed from it by milk of lime (Sec. 30, letter _i._), and there remained behind one-half of pure fire-air.