The most concentrated solution of nitrate of ammoniac capable of existing at 60°, is of specific gravity 1,304, and contains 33 water, and 67 fibrous salt, per cent. When this solution is evaporated at temperatures between 60° and 100, the salt is increased in weight by the addition of water of crystalisation, and no portion of it is lost.
During the evaporation of solutions of specific gravity 1,146 and 1,15, at temperatures below 120°, I have never detected any loss of salt. When the temperature of evaporation is 212°, the loss is generally from 3 to 4 grains per cent; and when from 230° to the standard of their ebullition, from 4 to 6 grains.
In proportion as solutions are more diluted, their loss in evaporation at equal temperatures is greater.
DIVISION III.
Decomposition of NITRATE of AMMONIAC: preparation of RESPIRABLE NITROUS OXIDE; its ANALYSIS.
I. Of the heat required for the decomposition of
NITRATE of AMMONIAC.
The decomposition of nitrate of ammoniac has been supposed by Cornette[78] to take place at temperatures below 212°, and its sublimation at 234°.
Kirwan, from the non-coincidence in the accounts of its composition, has imagined that it is partially decomposable, even by a heat of 80°.[79]
To ascertain the changes effected by increase of temperature in this salt, a glass retort was provided, tubulated for the purpose of introducing the bulb of a thermometer. After it had been made to communicate with the mercurial airholder, and placed in a furnace, the heat of which could be easily regulated, the thermometer was introduced, and the retort filled with the salt, and carefully luted; so that the appearances produced by different temperatures could be accurately observed, and the products evolved obtained.
From a number of experiments made in this manner on different salts, the following conclusions were drawn.