INFLAMMABLES. 311 



6. DECOMPOSITION. 



(a.) Driven in vapor through a red hot platinum tube, or a small 

 tube of glass or porcelain, this acid is decomposed, and affords sul- 

 phurous acid gas, two volumes, and oxygen gas one volume. 



(b.) Its decomposition is best effected upon one of its salts, as will 

 be mentioned under sulphate of baryta, from which we can obtain the 

 sulphur. 



(c.) Heated with charcoal powder, it is decomposed, and various 

 gases are evolved, as will be mentioned farther on. 



(d.) When it chars any animal or vegetable substance, it suffers 

 decomposition. 



Se.) Decomposed by galvanism sulphur appears at the negative, 

 oxygen at the positive pole, platinum wires being used. 

 (/.) By being passed through an ignited porcelain tube along with 

 hydrogen, which unites with its oxygen and precipitates the sulphur, 

 and perhaps evolves sulphurous acid gas. 



7. PROPORTION OF ITS CONSTITUENTS AND COMBINING WEIGHT. 

 (a.) Centesimal ratio. Writers vary between 43.28 sulphur, and 



56.72 oxygen, and 40 sulphur and 60 oxygen. Dr. Wollaston ad- 

 mits the latter numbers, and Berzelius those that approximate to 

 them ; 40 and 60 are probably correct. Murray. 



(b.) Equivalent numbers. The proportions of 40 and 60, corres- 

 pond with 1 6 of sulphur, 1 proportion, and 24 of oxygen, 3 propor- 

 tions, making 40 for the representative number of the dry acid, and 

 liquid sulphuric acid = 1 real acid, 40, and 1 of water 9 49. 



It is supposed that by volume, the sulphur would be represented 

 by 100, and the oxygen gas by 150, for oxygen gas is considered as 

 combining in the proportion of half a volume which would be 50, if 

 the 1 proportion of sulphur is called 100, and there are 3 of oxygen, 

 which would of course be 150. 



8. ANHYDROUS ACID. 



(a.) The dark fuming acid, already mentioned as being obtained 

 by distilling green vitriol, has a sp. gr. of 1.896 or 1.90, and boils 

 from 102 to 122 Fahr. 



(b.) Heated in a glass retort to which a receiver is attached, sur- 

 rounded by snow and salt, half of the acid passes over in a state re- 

 sembling asbestos, and is regarded as sulphuric acid without water, 

 or the anhydrous acid, and the acid remaining in the retort is like 

 the common oil of vitriol, composed of acid one proportion, and water 

 one. 



(c.) It is the pure acid without water. 



(d.) It smokes violently when exposed to the air, and is dissipated 

 too speedily to admit of being weighed. It is less corrosive than 

 common sulphuric acid. It crystallizes in tough silky filaments like 



