Experiments on Ammonia. 371 



The avidity with which ammonia retains moisture, and 

 again absorbs it when artificially dried, is very remarkable, 

 A confined quantity of common air may be completely de- 

 siccated, in the space of a few minutes, by pure potash, or 

 by muriate of lime; so that no ice shall appear in the inner 

 surface of the containing vessel when exposed to a cold of 

 — 26° of Fahrenheit. But ammonia requires exposure 

 during some hours to potash, to stand the test even of O" 

 Fahrenheit ; and a single traasfer of the dried gas, through 

 the mercury of a trough in ordinary use, again communi- 

 cates moisture to it. Muriatic acid gas, freed merely from 

 visible moisture, deposits no water at the temperature 

 of 26^ Fahrenheit. This is probably owing to its strong 

 affinity for water; for electricity, after the full action of 

 muriate of lime, evolves, as I have lately ascertained, about 

 l-3jth its bulk of hydrogen gas; the recent muriatic acid 

 gas giving about I -14th after the same treatment*. 



From the average of a great number of experiments on 

 the decomposition of ammonia by electricity, I was for 

 some time led to believe that you had rather under-stated 

 the proportion of permanent gases obtainable from it by 

 this process (viz. 103 measures of permanent gas from 60 

 of ammonia, or ISO from 100). For the most part, I had 

 found the bulk of ammonia to be doubled by decomposi- 

 tion, even when the gas was previously dried with extreme 

 care. In one instance a small bit of dry potash was left in 

 tlie tube, along wiih the ammonia, during electrization, 

 with the view of its absorbing water, which I supposed at 

 that time to be generated by the process. In this case, 5y 



any water thrit may have been generated by electricity. But though this 

 supposition may exulain the non-appearance of visible moisture, it does not 

 account for the ineniclency of a powerful cooling cause to discover traces of 

 watery vapour ; for this is a test which renders apparent very minute quan- 

 tities of water in gases. 



• In a course of experiments, which I have described in the PhilosophjcaJ 

 Transactions for 1800, it appeared that muriatic acid gas, after being dried 

 by muriate of lime, gave nearly as much hydrogen by electrization as ga» 

 which had not been thus exposed. I was not however aware, at that time, 

 of the extreme caution necessary in experiments of this icind ; and was sa- 

 tisfied with transferring the acid gas from a large vessel, in which it had 

 been dried, into the electrizing tube, a mode of proceeding which I now 

 find to be quite iuadmishible. The action of muriate of lime, which has 

 undergone fusion, on muriatic acid gas, is rendered very sensible, wheD 

 consid'.rable quantities are used, by the evolution of much heat, and by a 

 dimiiiutio!! of the volume of the gas. Ammonia aUo is contracted in bulk 

 bv dry ciiiutic potash. Muriate of lime eaimot be employed for its desic- 

 cation, since this substance ra|)idly absorbs the alkaline gas, even when the 

 gas li.:?. been previously exposed to quicklime. \u this case tht ammonia 

 attract . a portion of muriatic acid from the earthy salt agreeably to the law 

 of altiniiy, which has been 6U ably iUustratcd by Uertbollct. 



A a 2 measures 



