VOL. XC.1 PHILOSOPHICAL TRANSACTIONS. 643 



muriatic acid gas, in its recent state, and after exposure to muriate of lime, con- 

 vinced me that it was impossible, by this method, wholly to deprive the muriatic 

 gas of water. The recent gas however, when electrified in smaller quantity than 

 in exper. I, gave a larger proportion of hydrogenous gas; which shows, that some 

 portion of its moisture was removed by exposure to muriate of lime. In order, if 

 possible, to procure the gas perfectly dry, another mode of preparing it was re- 

 sorted to. Alum and common salt were first well 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 experi- 

 ment, it still, after the usual electrization, 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 certain point, beyond which it could not 

 be carried by continuing the shocks. Gas also, which had been thus treated, 

 when transferred to another tube, and again electrified, did not exhibit any further 

 deposit. It became interesting therefore to know, whether the production of 

 hydrogenous gas had a similar limitation; because the decision of this question 

 would go far towards ascertaining its source. If the evolved hydrogenous gas arose 

 from the decomposition of the acid, it might be expected to be produced, 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. 



Exper. 3 and 4. Into 2 separate tubes, I passed known quantities of muriatic 

 acid gas. Through the one portion 200 discharges were taken ; and through the 

 other 400. On comparing the quantities of hydrogenous gas produced, it proved 

 to bear exactly the same proportion, in each tube, to the gas originally 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 appears also, 

 from the following experiments, to be exerted, not only in disuniting the elements 

 of water, but in promoting the union of the evolved oxygen with muriatic acid. 



Exper. 5. A mixture of common air and muriatic acid gas, in the proportion of 

 143 of the former to ll6 of the latter, was rapidly diminished by electrical shocks; 

 30 of which reduced the whole to 111*. The remainder consisted of muriatic 

 acid and azotic gases, with a small proportion of oxygenous gas. The deposit 

 formed on the tube was of the same kind as before, but much more abundant. 



Exper. 6. The same appearances were occasioned, much more remarkably, by 

 electrifying muriatic acid with oxygenous gas; and the contraction continued till 

 the mercury rose so as to touch the extremity of the platina conductor. At each 



* This experiment suggests an additional reason, to that already given, for the greater diminution of 

 the first, than of the subsequent portions of muriatic acid gas ; for the former may be presumed to have 

 been much more adulterated than the latter, with the atmospherical air of the vessels. — Orig. 



4 N2 



