Part 6 (1/2)
Hey, an ingenious surgeon in Leeds a case presently occurred, in which he had an opportunity of giving it a trial; and mentioning it to Dr.
Hird and Dr. Crowther, two physicians who attended the patient, they approved the scheme, and it was put in execution; both by applying the fixed air by way of clyster, and at the same time making the patient drink plentifully of liquors strongly impregnated with it. The event was such, that I requested Mr. Hey to draw up a particular account of the case, describing the whole of the treatment, that the public might be satisfied that this new application of fixed air is perfectly safe, and also, have an opportunity of judging how far it had the effect which I expected from it; and as the application is new, and not unpromising, I shall subjoin his letter to me on the subject, by way of _Appendix_ to these papers.
When I began my inquires into the properties of different kinds of air, I engaged my friend Dr. Percival to attend to the _medicinal uses_ of them, being sensible that his knowledge of philosophy as well as of medicine would give him a singular advantage for this purpose. The result of his observations I shall also insert in the Appendix.
FOOTNOTES:
[5] Some time after these papers were first printed, I was pleased to find the same proposal in _Dr. Alexander's Experimental Essays_.
SECTION V.
_Of AIR in which a mixture of BRIMSTONE and FILINGS of IRON has stood._
Reading in Dr. Hales's account of his experiments, that there was a great diminution of the quant.i.ty of air in which _a mixture of powdered brimstone and filings of iron, made into a paste with water_, had stood, I repeated the experiment, and found the diminution greater than I had expected. This diminution of air is made as effectually, and as expeditiously, in quicksilver as in water; and it may be measured with the greatest accuracy, because there is neither any previous expansion or increase of the quant.i.ty of air, and because it is some time before this process begins to have any sensible effect. This diminution of air is various; but I have generally found it to be between one fifth and one fourth of the whole.
Air thus diminished is not heavier, but rather lighter than common air; and though lime-water does not become turbid when it is exposed to this air, it is probably owing to the formation of a selenitic salt, as was the case with the simple burning of brimstone above-mentioned. That something proceeding from the brimstone strongly affects the water which is confined in the same place with this mixture, is manifest from the very strong smell that it has of the volatile spirit of vitriol.
I conclude that the diminution of air by this, process is of the same kind with the diminution of it in the other cases, because when this mixture is put into air which has been previously diminished, either by the burning of candles, by respiration, or putrefaction, though it never fails to diminish it something more, it is, however, no farther than this process alone would have done it. If a fresh mixture be introduced into a quant.i.ty of air which had been reduced by a former mixture, it has little or no farther effect.
I once observed, that when a mixture of this kind was taken out of a quant.i.ty of air in which a candle had before burned out, and in which it had stood for several days, it was quite cold and black, as it always becomes in a confined place; but it presently grew very hot, smoaked copously, and smelled very offensively; and when it was cold, it was brown, like the rust of iron.
I once put a mixture of this kind to a quant.i.ty of inflammable air, made from iron, by which means it was diminished 1/9 or 1/10 in its bulk; but, as far as I could judge, it was still as inflammable as ever.
Another quant.i.ty of inflammable air was also reduced in the same proportion, by a mouse putrefying in it; but its inflammability was not seemingly lessened.
Air diminished by this mixture of iron filings and brimstone, is exceedingly noxious to animals, and I have not perceived that it grows any better by keeping in water. The smell of it is very pungent and offensive.
The quant.i.ty of this mixture which I made use of in the preceding experiments, was from two to four ounce measures; but I did not perceive, but that the diminution of the quant.i.ty of air (which was generally about twenty ounce measures) was as great with the smallest, as with the largest quant.i.ty. How small a quant.i.ty is necessary to diminish a given quant.i.ty of air to a _maximum_, I have made no experiments to ascertain.
As soon as this mixture of iron filings with, brimstone and water, begins to ferment, it also turns black, and begins to swell, and it continues to do so, till it occupies twice as much s.p.a.ce as it did at first. The force with which it expands is great; but how great it is I have not endeavoured to determine.
When this mixture is immersed in water, it generates no air, though it becomes black, and swells.
SECTION VI.
_Of NITROUS AIR._
Ever since I first read Dr. Hales's most excellent _Statical Essays_, I was particularly struck with that experiment of his, of which an account is given, VOL. I, p. 224. and VOL. II, p. 280. in which common air, and air generated from the Walton pyrites, by spirit of nitre, made a turbid red mixture, and in which part of the common air was absorbed; but I never expected to have the satisfaction of seeing this remarkable appearance, supposing it to be peculiar to that particular mineral.
Happening to mention this subject to the Hon. Mr. Cavendish, when I was in London, in the spring of the year 1772, he said that he did not imagine but that other kinds of pyrites, or the metals might answer as well, and that probably the red appearance of the mixture depended upon the spirit of nitre only. This encouraged me to attend to the subject; and having no pyrites, I began with the solution of the different metals in spirit of nitre, and catching the air which was generated in the solution, I presently found what I wanted, and a good deal more.
Beginning with the solution of bra.s.s, on the 4th of June 1772, I first found this remarkable species of air, only one effect of which, was casually observed by Dr. Hales; and he gave so little attention to it, and it has been so much unnoticed since his time, that, as far as I know, no name has been given to it. I therefore found myself, contrary to my first resolution, under an absolute necessity of giving a name to this kind of air myself. When I first began to speak and write of it to my friends, I happened to distinguish it by the name of _nitrous air_, because I had procured it by means of spirit of nitre only; and though I cannot say that I altogether like the term, neither myself nor any of my friends, to whom I have applied for the purpose, have been able to hit upon a better; so that I am obliged, after all, to content myself with it.
I have found that this kind of air is readily procured from iron, copper, bra.s.s, tin, silver, quicksilver, bis.m.u.th, and nickel, by the nitrous acid only, and from gold and the regulus of antimony by _aqua regia_. The circ.u.mstances attending the solution of each of these metals are various, but hardly worth mentioning, in treating of the properties of the _air_ which they yield; which, from what metal soever it is extracted, has, as far as I have been able to observe, the very same properties.
One of the most conspicuous properties of this kind of air is the great diminution of any quant.i.ty of common air with which it is mixed, attended with a turbid red, or deep orange colour, and a considerable heat. The _smell_ of it, also, is very strong, and remarkable, but very much resembling that of smoking spirit of nitre.
The diminution of a mixture of this and common air is not an equal diminution of both the kinds, which is all that Dr. Hales could observe, but of about one fifth of the common air, and as much of the nitrous air as is necessary to produce that effect; which, as I have found by many trials, is about one half as much as the original quant.i.ty of common air. For if one measure of nitrous air be put to two measures of common air, in a few minutes (by which time the effervescence will be over, and the mixture will have recovered its transparency) there will want about one ninth of the original two measures; and if both the kinds of air be very pure, the diminution will still go on slowly, till in a day or two, the whole will be reduced to one fifth less than the original quant.i.ty of common air. This farther diminution, by long standing, I had not observed at the time of the first publication of these papers.