360 
DE. E. DIVEES ON THE UNION OF 
prevented, increases its capability of dissolving more nitrate, and lessens that of 
condensing more ammonia. On cooling the liquid, saturated or nearly so with nitrate, 
some of the salt crystallizes out in long prisms, exactly like those that form in an 
aqueous solution ; on restoring the temperature these crystals redissolve. When the 
liquid is warmed, it gives off ammonia gas with the phenomenon of ebullition, not that of 
effervescence. Like many aqueous solutions, the liquid can be heated a little above 
its boiling-point without boiling, and be cooled below its crystallizing point without 
crystallizing, until it is disturbed, when ebullition or crystallization, as the case may be, 
takes place with suddenness. On boiling away the ammonia, or expelling it at a 
temperature below that of ebullition, the nitrate crystallizes out, just as it would do in 
similar circumstances from its aqueous solution. When the liquid is exposed to the 
air it instantly becomes crusted over with a film of nitrate, which is coherent, transparent, 
and apparently not crystalline. In consequence of this the liquid poured out on to a flat 
surface, sometimes even in the act of flowing from the mouth of the bottle, takes the 
appearance, though not the consistence, of jelly. On touching this apparent jelly, 
unchanged liquid breaks through the crust ; and by stirring the mass about in a dry 
atmosphere, nothing but solid ammonia nitrate at length remains. When the crust is 
not broken, it preserves the enclosed liquid for a long time from further evaporation in 
dry weather. 
The liquid is colourless, and as mobile as any aqueous saline solution. It smells very 
powerfully of ammonia, unless it be allowed to crust over, when this smell is almost 
wanting. It has not a slimy feel between the fingers like an alkali lye, and seems, 
indeed, to have no caustic power. It boils when poured on the skin, and gives rise to a 
slight feeling of crepitation, but it produces only a feeble sensation of cold. 
4. The quantity of ammonia that can be condensed by the nitrate varies with the 
pressure and temperature, and appears to be quite independent of the atomic relations 
of the two substances. At the pressure of the atmosphere and at a temperature of 
0°, ammonia nitrate can condense almost exactly half its weight of ammonia. Its 
condensing-power, therefore, exceeds that of water at the same temperature. The 
ratio of two parts nitrate to one of ammonia is about that of 3NO ;J H . NH 3 : 7NH 3 ; but 
there is nothing to support the view that the liquid is a definite molecular com- 
bination. 
To determine the limit just stated of the condensing-power of the nitrate upon 
ammonia gas, at 0° and the atmospheric pressure, the closed flask containing the nitrate 
was weighed, and from the weight found was deducted that of the empty flask, its 
stopper, and an iron wire that served both to suspend the flask to the balance and also 
afterwards to bind down the stopper. The flask generally employed was one adapted 
for taking the specific gravity of the liquid, and which shall be more particularly 
described in connexion with that operation. The quantity of nitrate employed weighed 
from 35 to 45 grains. When the ammonia had been passed into the flask, surrounded 
with ice, for some time after absorption had apparently ceased, the delivery-tube was 
