The solution was now pale green, that is, of its natural color, and a considerable quantity of red oxide of iron had been deposited.
Solid caustic potash was introduced into it, till all the green oxide of iron had been precipitated, and till the solution rendered green, red cabbage juice.
A tube was now accurately connected with the mattrass, bent, and introduced into a small quantity of diluted sulphuric acid. Nearly half of the fluid in it was slowly distilled into the sulphuric acid, by the heat of a spirit lamp. The impregnated acid evaporated at a heat above 212°, and gave a small quantity of crystalised salt, which barely amounted to two grains and quarter: it had every property of sulphate of ammoniac. Sulphuric acid in excess was poured on the residuum, and the whole distilled by a heat not exceeding 300°, into a small quantity of water. This water, after the process, tasted strongly of sulphuric acid; it had no peculiar odor. Tin thrown into it when heated, was not perceptibly oxydated; mingled with strontitic lime water, it gave a copious white precipitate, and after the precipitation became almost tasteless. Hence it evidently contained no nitric acid.
The 12,5 cubic inches of undecompounded gas that came over were examined; and accounting for the small quantity of common air previously contained in the airholder, must have been almost pure.
l. Now supposing 927 grains of the impregnated solution (including the weight of the nitrous gas), to have been operated upon, this must have contained about 16,7 cubic inches of nitrous gas. But 12,5 cubic inches escaped undecompounded: hence 4,2 were decomposed; and these weigh 1,44 grains, and are composed of,8 oxygene, and,64 nitrogene.[117]
Consequently, the nitrous gas must have furnished,8 of oxygene to the green oxide of iron.
But,64 of nitrogene require,15 of hydrogene to form,79 of ammoniac:[118] consequently 1 of water was decompounded, and this furnished,85 of oxygene to the green oxide of iron.
The green oxide of iron contains ²⁷/₁₀₀ oxygene; the red ⁴⁸/₁₀₀. But the whole quantity of oxygene supplied from the water and nitrous gas is 0,8 + 0,85 = 1,65; and calculating on the difference of the composition of the red and green oxide of iron, 5,7 grains of red oxide must have been deposited, and consequently these would saturate as much acid as,79 grains of ammoniac, or 4,1 grains of green oxide of iron.[119]
And supposing the ammoniac in sulphate of ammoniac to be to the acid as 1 is to 3,[120] 3.2 grains of sulphate of ammoniac must have been formed, containing about 2,4 grains acid; and then 6,5 grains of green sulphate of iron must have been decomposed.
Hence we gain the following equation: