304 EXPERIMENTS AND OBSERVATIONS 



view under which it may be regarded as present, as an adven- 

 titious ingredient. The acid having a strong attraction to 

 water, may be supposed, in the processes in which it is usually 

 prepared, to retain a portion not strictly essential to its con- 

 stitution as muriatic acid gas, but still chemically combined, — 

 that is, combined with it with such an attraction as to be libe- 

 rated only when it passes into other combinations, and it may 

 be this portion which is obtained in the action of metals on 

 the gas ; the other portion, that essential to the acid, being suf- 

 ficient to produce the requisite oxidation of the metal. 



The question with regard to the existence of water in this 

 state, Gay Lussac and Thenard ' have already determined. 

 From an extensive series of experiments, they found reason to 

 conclude, that muriatic acid gas, in whatever mode it is pre- 

 pared, is uniformly the same. From the quantity of hydrogen 

 gas which combines with oxymuriatic gas in its formation, it 

 follows, that it contains 0.25 of water, essential to its constitu- 

 tion. But the gas obtained by the usual processes, afforded, 

 they found, exactly 0.25 of water, when transmitted over oxide 

 of lead, or combined with oxide of silver ; and the same com- 

 pounds are formed, as by the action of oxymuriatic acid on sil- 

 ver and lead in their metallic state. They prepared muriatic 

 acid gas, by heating fused muriate of silver with charcoal mo- 

 derately calcined. It contained just the same quantity of wa- 

 ter as muriatic acid obtained from humid materials, as it af- 

 forded the same quantity of hydrogen from the action of po- 

 tassium. And instead of being capable of receiving the small- 

 est additional portion of water, a single drop of water being in- 

 troduced into three quarts of it, did not disappear, nor even 

 diminish, but, on the contrary, increased in volume *. These 



facts 



* Recherches Physico-chimiques, t. ii. p. 133. 



