10 



C H R M I S T R V. 



Iti specific gravity, according to Kirwan, i 1.103; 

 according to Davy, 1.127; according to Fourcroy, 

 Vlu queliii, and Srguin, 1.087 ; according to Saus- 

 ure, junior, 1.114, that of air being 1.000. At 

 the temperature of 60, nd when the barometer 

 stands at 30 inches, 100 cubic inches of common air 

 weigh very nearly 30.5 grains troy. 100 cubic 

 inches of oxygen in the same temperature and pres- 

 sure, wfi^h, according to these results, 33. grain', 

 34.37 grains, 33.15 grains, and 33.97 grains troy. 



It is not sensibly absorbed by water. 100 cubic 

 inches of water freed from air by boiling, absorb 



>~> inches of this gas, according to the experiments 

 of Dr Henry. 



Oxygen is capable of combining with a great num- 

 ber of bodies, or it has an affinity for them, and 

 forms compounds with them. 



SECT. II. Of Chhrine. 



This substance was first discovered by Scheele, 

 and called by him depklogi<ticated muriatic acid. 

 Berthollet, who made many important experiments 

 on it, and who conceived it to be a compound of 

 muriatic acid and oxygon, gave it the name of oxy- 

 Mow pro muriatic acid. Mr Davy has lately made it the sub- 

 cured. : ect o f investigation, and has published some very 

 important dissertations on it. He has shewn, by 

 decisive experiments, that we have no proof of its 

 containing oxygen. This has induced him to re- 

 vive the original opinion of Scheele respecting its 

 nature, and convinced of the impropriety of the old 

 names by which it was distinguished, and aware of 

 the hazard of giving it a name from theoretical con- 

 siderations, he has contrived the term clilorinc, de- 

 rived from the green colour, by which it may be dis- 

 tinguished from all other gaseous bodies. 



Chlorine may be obtained by distilling a mixture 

 of muriatic acid and the black oxide of manganese ; 

 or by mixing together three parts of common salt, 

 and two parts of black oxide of manganese in a glass 

 retort, and pouring over them two parts of diluted 

 sulphuric acid. When this mixture is heated, a grei-n 

 coloured gas makes its appearance, which may be 

 collected in glass phials over water. This gas is the 

 substance in question. 



Its proper- This gas has a yellowish green colour, its odour is 

 tie*. extremely offensive and suffocating, and it cannot be 



breathed. When drawn into the lungs mixed with 

 common air, it occasions a violent cough, which lasts 

 for some time, accompanied with a sense of oppres- 

 sion and of weakness. It is capable of supporting 

 combustion. Indeed, many substances, as phospho- 

 rus, antimony, Sec. take fire m it of their own ac- 

 cord, without being kindled. Its specific gravity is 

 2.713, that of air being 1.000. 



It is not altered by exposure to light, or to a red 

 heat. 



Water absorbs it slowly, and acquires a green co- 

 lour, and the smell and properties of the gas. It 

 may be frozen without losing the gas, but it is easi- 

 ly extricated by heat. When this liquid ia exposed 

 to the light, the chlorine disappears, oxygen gas es- 

 capes, and a portion of muriatic acid is found dis- 

 solved in the water. 



r, 



Chlorine has the property of destroying vegetable Elements 

 blues, and other vegetable colours. This property , , ' 

 has rendered it a valuable article in bleaching. ^iimnt^y. 



Oxygen has the property of combining with chlo- E,, c |J r ; c 

 rim-, and of forming with it a peculiar yellow-co- gav. 

 loured gas, hitherto not much examined. It was 

 discovered by Mr Davy. To obtain it, the salt 

 formed by pasting a current of chlorine through a 

 solution of carbonate of potash, a salt formerly dis- 

 tinguished by the name of hyper-oxymuriate of pot- 

 ash, is put into a flask, and diluted muriatic acid 

 oured upon it. An effervescence takes place ; and, 

 y the cautious application of a very moderate heat, 

 the combination in question comes over. Mr Davy 

 proposes to dibtinguisli this new gas by the name of 

 euthloric gas, in consequence of the great intensity 

 of its colour. Combustible substances do not act 

 upon this gas so powerfully as upon chlorine. In- 

 deed, the metals do nut act upon it at all till it is de- 

 composed. When expo.-ed t i a moderate heat, it is 

 decomposed, and the expansion is accompanied by 

 an explosion. 



As far as we know at present, chlorine, like oxy- 

 gen, is a simple substance ; and it is, in some re- 

 spects, a more powerlul supporter of combustion 

 than oxygen itself. 



Like oxygen, it has an affinity for a great num- 

 ber of bodies, and forms peculiar compounds by 

 uniting with them. 



CHAP. II. 

 Of Simple Combustibles. 



BY combust i MK is understood a substance capable simple 

 of burning ; and by simple combustibles, bodies of combusti. 

 that nature not yet decomposed. They are five in Wei. 

 number, namely, hydrogen, carbon, plxixpliomi, sul- 

 phur, and boracittm. It is not impossible that the 

 bases of all or most of these substances are metals ; 

 but the opinion has not yet been made out in a satis- 

 factory manner. 



SECT. I. Of Hydrogen. 



Hydrogen, like oxygen, is a gas. It was first n y arogen. 

 called inflammable air, and Mr Cavendish must be 

 considered as its real discoverer. 



It may be procured by putting some clean iron or HOW pro- 

 zinc filings into a glass retort, and pouring over them cured, 

 sulphuric acid diluted with thrice its bulk of water. 

 A violent boiling takes place, or, as chemists term 

 it, an effervescence ; gas issues abundantly from the 

 beak ofthe retort, and may be received like the oxy- 

 gen in glass vessels standing in a trough of water. 



It is invisible and colourless, and possesses the me- lit proper- 

 chanical properties of common air. ** 



When prepared by the above process, it has a pe- 

 culiar smell, ascribed at present to the presence of a 

 little oil, formed by the action of the acid on the 

 iron filings. 



It is the lightest gaseous body known. Its spe- 

 cific gravity, according to Kirwan, is 0.0843 ; ac- 

 cording to Lavoisier, 0.0756 ; according to Four- 

 3 



