VII. Non-existence of Ammoniacal Nitrites.
I attempted in different modes to combine nitrous acids with ammoniac, so as to form the salts which have been supposed to exist, and called nitrites of ammoniac; but without success.
I first decomposed a solution of carbonate of ammoniac by dilute olive colored acid; but in this process, though no heat was generated, yet all the nitrous gas appeared to be liberated with the carbonic acid.[75] I then combined a small quantity of nitrous gas, with a solution of nitrate of ammoniac. But after evaporating this solution at 70°-80°, I could not detect the existence of nitrous gas in the solid salt; it was given out during the evaporation and crystalisation, and formed into nitrous acid by the oxygene of the atmosphere. I likewise heated nitrate of ammoniac to different degrees, and partially decomposed it, to ascertain if in any case the acid was phlogisticated by heat: but in no experiment could I detect the existence of nitrous acid in the heated salt, when it had been previously perfectly neutralised.
When nitrate of ammoniac, indeed, with excess of nitric acid, is exposed to heat, the superabundant nitric acid becomes phlogisticated, and is then liberated from the salt, which remains neutral.[76]
We may therefore conclude that nitrous gas has little or no affinity for solid nitrate of ammoniac, and that no substance exists to which the name nitrite of ammoniac can with propriety be applied.
VIII. Of the sources of error in Analysis.
To compare my synthesis of nitrate of ammoniac with analysis, I endeavoured to separate the ammoniac and nitric acid from each other, without decomposition. But in going through the analytical process, I soon discovered that it was impossible to make it accurate, without many collateral laborious experiments on the quantities of ammoniac soluble in water at different temperatures.
At a temperature above 212°, I decomposed, by caustic slacked lime, 50 grains of compact nitrate of ammoniac in a retort communicating with the mercurial airholder, the moisture in which had been previously saturated with ammoniac. 22 cubic inches of gas were collected at 38°, and from the loss of weight of the retort, it appeared that 13 grains of solution of ammoniac in water, had been deposited by the gas.
Now evidently, this solution must have contained much more alkali in proportion to its water than that of 55°, otherwise the quantity of ammoniac in 50 grains of salt would hardly equal 8 grains.[77]
IX. Of the loss of Solutions of Nitrate of Ammoniac
during evaporation.