192 Mr. Henry's Account of Experiments 



calcined, separately, to expel their water of crystallization, and, 

 being then mixed, were distilled together in an earthen retort. 

 The gas proceeding from these materials, was received over 

 dry mercury ; but, though only the last portion that came over 

 was reserved for experiment, it still, after the usual electriza- 

 tion, afforded a product of hydrogenous gas. 



In the course of the preceding experiments, I observed that 

 the diminution of the muriatic acid gas stopped always at a cer- 

 tain point, beyond which it could not be carried by continuing 

 the shocks. Gas also, which had been thus treated, when trans- 

 ferred to another tube, and again electrified, did not exhibit any 

 further deposit. It became interesting, therefore, to know, whe- 

 ther the production of hydrogenous gas had a similar limitation ; 

 because, the decision of this question would go far towards ascer- 

 taining its source. If the evolved hydrogenous gas arose from 

 the decomposition of the acid, it might be expected to be pro- 

 duced, as long as any acid remained undecomposed. But, if 

 water were the origin of this gas, it would cease to be evolved, 

 when the whole of the water contained in the gas had been 

 resolved into its constituent principles. 



Experiments 3 and 4. Into two separate tubes, I passed known 

 quantities of muriatic acid gas. Through the one portion, 200 

 discharges were taken ; and through the other, 400. On com- 

 paring the quantities of hydrogenous gas produced, it proved to 

 bear exactly the same proportion, in each tube, to the gas origi- 

 nally submitted to experiment. Hence it may be inferred, that 

 the hydrogenous gas, evolved by electrifying the muriatic acid, 

 has its origin, not from the acid, but from the water which is 

 intimately attached to it. The agency of the electric fluid ap- 

 pears also, from the following experiments, to be exerted, not 





