$50 EXPERIMENTS ON THE RELATION 
experiments very carefully conducted ; and we shall find, that 
though this salt, is not, perhaps in strict chemical language, 
deliquescent, yet it is capable of absorbing or attracting from 
the atmosphere a very notable portion of water. This, how- 
ever, may be totally expelled, by keeping the salt for a short 
time in a temperature of from 200° to 300° of Fahrenheit, 
when it resumes exactly its pristine weight. 
Pulverised sal ammoniac was desiccated in a platina capsule, 
at a heat somewhat below that of its sublimation. It was then 
found to weigh 49 gr. I placed the capsule on a shelf in my 
apartment. On re-weighing it, at the end of two days, the 
salt was found to have become heavier by 3.1 gr.; which 
amounts to more than six parts in the hundred. Sal ammo- 
niac from gaseous combination exhibits the same phenome- 
non; and probably, from the extreme comminution of the 
powder, to a still greater degree. It even becomes pasty. The 
quantity of this adhering or hygrometric water, will vary no 
doubt with the weather or climate, as is the case with muriate 
of soda *. 
It may be said, Since our sole object in decomposing sal am- 
moniac, by metallic lamina, is to obtain from its acid consti- 
tuent the water which it is supposed intimately to contain, and 
to carry into that salt ; why not employ directly dry muriatic 
acid gas, in such researches? My only answer is, that in de- 
siccated sal ammoniac, we conveniently find the acid in a state 
hygrometrically 
* In clear frosty weather, or in a very dry apartment, where muriate of lime 
would crystallise, the ammoniacal salt acquires weight very slowly. Fifty grains 
of that from gaseous combination, just heated in a platina capsule, to near its 
subliming temperature, being put into the scale of a sensible balance, became 
heavier by half a grain in two minutes ; after which, in the above circumstances, 
no further absorption of moisture was perceptible for an hour. The experiments 
detailed in the text were made, when the air was considerably loaded with mois- 
ture. 
