ox y

O X Y

( 190 )

tun’s rays. Of thefe the green confervaof ponds is a remarkable inftance, as Dr.Ingenhoufz has {hewn by experiment.

The fpecific gravity of oxygen gas accordingto Kirwan is 0.00135, or 740 times lighter thanwater, (at 30 inches bar. and 60° therm), and itis heavier than common air in the proportionof 1103 to 1000. The weight one hundred cubicinches of it is equal to 34 grains; but Mr. Davymakes it 35.06. The expanfion or contractionwhich it undergoes by changes in prefiure andtemperature, will be given in the appendix.

This gas is only in a very fmall degreeabforbed by water. According to Mr. Henry’sexperiments, 100 cubic inches of well boiledwater abforb 3.55 of oxygen. This folutionhas no particular fenfible qualities.

The characters that peculiarly diftinguifhoxygen gas, are the eminent degree in which itfupports combuftion and refpiration; and it isproved that neither of thefe can go on withoutoxygen, and that it is folely owing to its prefencethat atmofpheric air and the other compoundgaffes are fitted for maintaining thefe grandproceffes of the material world. The functionof refpiration will not be treated of in thiswork, it may therefore be merely mentioned inthis place, that if a fmall animal is immerfedin oxygen gas, it will live much longer than inthe fame quantity of common air, and if thecarbonic generated in the procefs be occa-fionally removed by alkalies, the animal willremain in the gas uninjured for a much greaterlength of time. In this and in many otherrefpecfs the proceffes of refpiration and com-buftion agree, but ftill there are fome circum-ftances which render it probable that the diluterftate of oxygen, (fuch as it exifts in commonair) is altogether fitter for animal refpirationthan a purer oxygen.

The burning of the feveral combuftible bodiesin oxygen gas, forms a number of molt beauti-ful and inftruCtive experiments, and has con-tributed more than any thing eli'e to giveaccurate ideas on the nature of combuftion ingeneral. Some of the experiments are thefollowing:

Immerfe a lighted taper in the gas, and itwill burn with a prodigious encreafe of rapidity,and a dazzling light.

Heat the top of a bit of charcoal red-hot,(which if merely left in the open air willfoon be covered with a white alh, and beextinguilhed) ; introduce it into oxygen gas,and the kindled part will fuddenly glow witha bright heat, and emiffion of brilliant fparks

for a certain time, after which it will go out.The bulk of the remaining gas is not muchaltered, but a large quantity of the oxygenwill be confirmed, and in its (lead muchcarbonic acid gas will be generated, whichwill inftantly render lime water milky whenfhaken with it, and may be removed by limeor alkalies. The weight of carbonic acid willbe found to equal the lofs fuftained by thecharcoal and by the oxygen united.

Introduce a fmall piece of phofphorus intoa large jar of oxygen, with an atom of lightedtinder in contaft with it. (,The belt apparatusfor thefe experiments will be mentioned in theappendix.) The phofphorus will burn with avaft body of bright light, fo brilliant that theeye can hardly fupport it, and with intenfe heatand rapid emiflion of white fumes. The heatat firft expands the gas, and if the jar is quitefull throws part of it out, but prefently thereis a rapid abforption, the water being fuckedup into the jar, and if the gas were quite purenone would be left. The white vapours arephofphoric acid , the product of the combuftion,and obvioully compounded of phofphorus andoxygen, as in the former experiment the car-bonic acid gas was produced by the union ofcharcoal and oxygen.

Provide a bottle with a cork perforated toadmit a glafs tube drawn out to a tolerably finepoint, and bent at right angles in the middie.Fill the bottle nearly full with very dilute ful-phuric or muriatic acid, and throw in feveralfmall bits of zinc. This will produce a copiousftream of hydrogen gas, which (when it has runto wafte for a Ihort time to expel the commonair of the bottle) kindle at the end of the glafstube, and immediately introduce it into the fideopening of a fmall tubulated receiver, full ofoxygen, through the perforation of a cork cutto fit exa£Hy, whilft the neck of the receiveris inverted over water. The ftream of hydrogenwill burn with an enlarged flame, and withoutany fmoke, and all the infide of the receiverwill be covered with a watery dew. The gaswill gradually difappear and the water rife.In this procefs (and others more accurate willbe mentioned under the article Water ) the foieprodudt is water, which therefore is producedby the union of hydrogen and oxygen at a hightemperature.

Make a fpiral coil of iron wire, and kindle it,and introduce it into oxygen gas. (The man-ner of performing the experiment is defcribedunder the article Iron, and in the Appendix )..After a moll brilliant combuftion the iron will