Discovery of Oxygen Part 3

I filled a bladder with the air which one obtains from iron filings and vitriolic acid (- 30, _c._), and respired it in the manner previously described (- 84). I was only able to inhale it 20 times, and after I had somewhat recovered, I expelled the air once more from my lungs as completely as possible, and again inhaled this inflammable air: after 10 inhalations I was compelled to desist from it, and observed that it could no longer be kindled, and also would not unite with lime water.

In one word it was a vitiated air.

I kept a piece of sulphur in continuous ebullition over the fire in a retort, capable of holding 12 ounces of water, with an empty bladder attached in place of a receiver, the retort also placed so that the sulphur which rose into the neck could run back again. After all had become cold, I found the air neither increased nor diminished: it smelt slightly hepatic, and extinguished a burning candle. I shall prove further on that sulphur can unite with more phlogiston; and it seems to me to follow from this experiment that something inflammable from the air had deposited itself upon the sulphur, and that the air had thereby acquired the property of a vitiated air. It is, however, also remarkable that other bodies which attract the inflammable substance more strongly, as for example, the fuming acid of nitre, do not abstract it from the air. It is likewise strange that I was able to inhale the inflammable air into my lungs only 20 times; and I observe here as something peculiar that, if I mistake not, I became very warm a quarter of an hour afterwards. It is also to be observed that fire-air, vitiated by the lungs, extinguishes fire; why does not the aerial acid attract the phlogiston again? why not also the vitiated air? Mr. Priestley indeed has accomplished this, but it did not succeed with me however much I also wished it. He has converted aerial acid into wholesome air by means of a mixture of iron filings, sulphur, and some water. When I desired to repeat this experiment, the aerial acid was always absorbed by the iron filings. I likewise powdered finely some iron filings which had been fused together with excess of sulphur, moistened this with water, and preserved it in a bottle which was filled with aerial acid: but with the same result. After 2 two days the aerial acid was almost entirely absorbed. This philosopher also says that he has made vitiated air wholesome again by agitation with water. I must admit, however, that with me this likewise failed. I filled a flask one fourth part with vitiated air, and the remainder with fresh water; I closed the flask very tightly, and shook it up and down for almost a whole hour. Then when I collected this air in a bladder, and from this in a bottle, I found that the candle was extinguished afterwards as it was before. He mixed with water, by agitation, the inflammable air from metals; this also would not succeed with me, although I used only little inflammable air, and much water. He also observed that plants made vitiated air wholesome again. It follows from my experiments that they vitiate air. I kept plants, in the dark as well as exposed to sunlight, in a flask which was filled with vitiated air and carefully secured (which careful securing must really be attended to). I tested a little of this air every 2 days, and always found it vitiated.

+94.+ Water has the peculiar property of separating the proximate const.i.tuents of air; of uniting with fire-air; and of entering into no kind of union with vitiated air. (1.) I filled a large bottle with boiled water which had been cooled shortly before, and permitted the tenth part to run out. I then placed the bottle, inverted and open, in a vessel with water. I observed the quant.i.ty of air to diminish a little every day, and when this diminution ceased, I collected the remaining air first in a bladder (- 30, _h._), and from the bladder in a bottle (- 30, _c._), and brought a burning candle into the bottle; it had scarcely reached the mouth when it went out. (2.) I then took the same kind of water freed from air, filled a bottle with it, and permitted the tenth part of it to run into a bladder filled with vitiated air. I next placed the bottle, inverted, in a vessel with water, and observed the s.p.a.ce which the air occupied in it. I found, 14 days afterwards, that the water had not absorbed the smallest quant.i.ty of it. (3.) I placed a large bottle, from which the bottom was knocked out, in a deep kettle with water, so that the water outside reached above the top of the bottle. I then tied a bladder, empty of air, over the top of the bottle, and made the water boil up once over the fire. The air which was in that portion of the water contained under the bottle rose into the bladder; and after I had tied up the bladder, and detached it front the bottle, I filled a phial with it, and put a small burning candle into it; it burned there more brightly than in ordinary air.

This fire-air, dissolved in water, must be as indispensable for aquatic animals as for those which live upon the earth. They must draw it into their bodies, and convert it either into aerial acid or into vitiated air. Into whichever kind it is, however, it must always become separated from the water again, for as aerial acid it does not remain with the water in the open air, and vitiated air cannot unite with water at all (No. 2), the water is then in a condition again to absorb fire-air anew, and to convey it to the animals. My experiments made with respect to this matter agree with this entirely. I allowed a few leeches to remain in a bottle, which was half filled with water and well closed, until they died. I then examined the air standing over this water. It had no smell, nor had the water; it appeared to have increased a little and it extinguished fire. It seems that these creatures live only upon the phlogiston in fire-air, perhaps also upon the heat. I have preserved them alive in water, and that the same water, for two years; the bottle was only tied over with gauze. I have a convenient method to ascertain whether fire-air is present in water or not. I take, for example, an ounce of it, and add to it about 4 drops of a solution of vitriol of iron, and 2 drops of a solution of alkali of tartar which has been somewhat diluted with water. A dark green precipitate is immediately formed, which, however becomes yellow in a couple of minutes if the water contains fire-air; but if the water has been boiled, and has become cold without access of air, or if it is even a recently distilled water, the precipitate retains its green colour, and does not become yellow sooner than an hour afterwards, and not yellow at all if it is protected from access of air in full bottles. I have already shown (- 15) that the green precipitate of iron owes its colour to phlogiston which still adheres to the earth, and it follows from this that fire-air, although not in the elastic condition, is able to attract phlogiston. The following experiment likewise shewed me that aquatic animals take fire-air from the water. I placed a leech in a bottle which was completely filled with water, and was protected from every kind of air. After two days it was almost dead. I then examined the water in the manner described above, and found that the earth of iron retained its green colour. The swelling up of peas in cold water is to be ascribed mainly to the fire-air present in the water. If a bottle is filled full of water and a few peas are placed in it, after 24 hours the water contains aerial acid it is true, but no fire-air. In water boiled and become cold, peas swell up only a little. I perceive in this the reason why the waters distilled from plants not only lose their smell, but why also a mucilaginous substance settles to the bottom, when the bottles are frequently opened, whereas the same waters, in perfectly full bottles, retain their smell and clearness unchanged. All plants communicate to water some mucilaginous material which is carried over along with it. Fire-air is the chief cause of this corruption; if this enters the water again, it attracts to itself the inflammable substance from the subtle oily and mucilaginous matter, and alters the whole of the water.