As a cheap mode of obtaining nitrate of ammoniac, Dr. BEDDOES proposed
to decompose nitre by sulphate of ammoniac, which is a well known
article of commerce. From synthesis of sulphate of ammoniac, compared
with analysis made in August 1799,[74] I concluded that 100 grains of
prismatic salt were composed of about 18 grains ammoniac, 44 acid, and
38 water; and supposing 100 grains of nitre to contain 50 acid, 100
grains of sulphate of ammoniac will require for their decomposition 134
grains of nitre, and form 90,9 grains of compact nitrate of ammoniac.
[74] And which will be published, with an account of its perfect
decomposition at a high temperature, in the _Researches_.
To ascertain if the sulphate of potash and nitrate of ammoniac could be
easily separated, I added to a heated saturated solution of sulphate of
ammoniac, pulverised nitre, till the decomposition was complete. After
this decomposition, the solution contained a slight excess of sulphuric
acid, which was combined with lime, and the whole set to evaporate at
a temperature below 250°. As soon as the sulphate of potash began to
crystalise, the solution was suffered to cool, and then poured off from
the crystalised salt, which appeared to contain no nitrate of ammoniac.
After a second evaporation and crystalisation, almost the whole of
the sulphate appeared to be deposited, and the solution of nitrate of
ammoniac was obtained nearly pure: it was evaporated at 212°, and gave
fibrous crystals.