on the Muriatic and Oxymuriatic Acids. 339 



■only when the muriate of lime has attracted moisture, either 

 from the atmosphere or the mercury, and is then owing to 

 a condensation of a part of -the gas. 



Essentially, the changes produced by electrifying muriatic 

 acid over mercury are those which I have stated ; viz. a con- 

 traction of the volume of the gas, the formation of muriate 

 of mercury (calomel), and the evolution of hydrogen. Re- 

 cent experiments, also, have confirmed the accuracy of the 

 observation*, that when a certain effect has been produced 

 by electricity, nothing is gained by continuing the process j 

 for neither is more hydrogen evolved, nor can the con- 

 traction of bulk be carried any further. 



I have lately applied, to experiments on muriatic acid, an 

 apparatus which I used advantaeeously for the analysis of 

 ammonia f. It consists of a spherical glass vessel, into 

 which are hermetically sealed two small tubes containing 

 I)latina wires, the points of which approach within the 

 striking distance. To the globular part is attached a neck, 

 which may be closed, as occasion requires, either by a glass 

 stopper or by a metal cap and stop-cock. Into a vessel of 

 this kind I introduced 4| cubic inches of muriatic acid 

 gas, and passed through it 3000 discharges from a Leyden 

 jar; at the close of the process, no traces of moisture could 

 be perceived on the inner surface of the vessel, nor could I 

 discover, on opening the stopper, that any change of bulk 

 had taken place. After absorbing the unchanged muriatic 

 acid gas by a small quantity of wat^r, a volume of gas re- 

 mained, in which there were present 100 measures (each 

 equal to one grain of mercurv) of oxynmriatic acid gas, 

 and 140 measures of hydrogen. Two causes might, per- 

 haps, contribute to diminish, in some degree, the propor- 

 tion of the former. It was difficult to exclude from the 

 apparatus, on admitting the muriatic acid gas into it, two 

 or three very niinute globules of mercury, which became 

 tarnished during the experiment, exactly as they would 

 have been by oxynmriatic acid ; and a small portion of the 

 latter gas was probably also taken up by the water employed 

 to absorb the muriatic acid. 



With the intention of uiving greater effect to the electri- 

 city, I repeated the experin)eni in a vessel capable of con- 

 taining not more than 1400 grains of quicksilver (about '4 J 

 of a cuijic inch), the neck of which, being only -J- of an 

 inch in diameter, was better calculated to show any minute 

 change in the volume of the gas. On removing the stop- 



• Phil. Trans. ISOO, p. 192. — Phil. Mag. vol. vii. p. 214. f Phil. 



Trani. 18U9. — Phil. Mdg.vul. xxxiv. 



Y 2 per^ 



