290 EXPERIMENTS AND OBSERVATIONS 



was repeated, obviating these sources of error as far as pos- 

 sible, the water obtained was in larger quantity. And as no 

 fallacy belongs to the conducting the experiment in the more 

 favourable mode in which it was first performed, (the assertion 

 of the absorption of water from the air being altogether un- 

 founded), the quantity procured in that mode is to be regarded 

 as the real result *. 



The argument was maintained, that the water might be deri- 

 ved from hygrometric vapour in the gases submitted to expe- 

 riment. Tins it was easy to refute. Dr Henry had shewn, 

 that ammonia after exposure to potash, and muriatic acid after 

 exposure to muriate of lime, retain no trace of vapour what- 

 ever. And these precautions had been very carefully observed. 

 The assertion was brought forward, too, only to account for the 

 minute quantity of water obtained in that mode of conducting 

 the experiment which affords the least favourable result, and 

 were it even admitted to all the extent to which it can be sup- 

 posed to exist, is inadequate to account for the larger quantity 

 obtained, in the other. 



That the entire quantity of water contained in the muriatic 

 acid gas, is not to be looked for, is evident from the nature of 

 the ammoniacal salt, particularly its volatility, whence the due 

 degree of heat to effect the separation of the water cannot be 

 applied. If the other muriates yield the greater part of their 

 water, only when raised nearly to a red heat, (which is the 

 case), it is not to be supposed that muriate of ammonia shall 

 do so at a temperature so much lower, as that which it can su- 

 stain without volatilization. What is to be expected, is a cer- 

 tain portion of water, greater as the arrangements employed 

 are better adapted to obviate the peculiar difficulty attending 



the 



* Nicholson's Journal, vol. xxxii. p. 1S6, &c. ; vol. xxxiv. p. 271. 



