Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/410

 the alkali by pure nitric acid, and subjecting the solution to the ordinary tests.

Fifty grains treated in the usual way, with nitrat of barytes, &c. furnished an alkaline salt, which when united with sulphuric acid, assumed the figure of sulphat of soda by crystallization. But the quantity of this salt was too small to admit of being weighed.

One hundred grains exposed to a red heat for a quarter of an hour, were diminished in weight one grain. Pure alkalies do not effect the decomposition of this mineral so easily as they do in the state of carbonate.

One hundred grains were mixed and fused with 400 grains of dried carbonat of soda, in a platina crucible. Treated with muriatic acid spongy Rocks of siliceous earth subsided. Ammonia precipitated from the decanted fluid a gelatinous matter of a reddish brown, which was sufficiently edulcorated; and after ignition, was treated with muriatic acid, which left a small portion of silica undissolved.

Sulphuric acid separated some gypsum. The contents of the solution were now thrown down by means of an alcoholic solution of potash, and the brown precipitated matter was boiled with a superabundant quantity of the precipitant. The clear alkaline fluid was treated with muriat of ammonia, which separated some alumina, but in a quantity too minute for collection. Though this circumstance occurred twice, I am disposed to think that the presence of alumina should be considered as an accidental intrusion. The brown precipitated matter consisted of oxide of iron with a trace of manganese. The first solution from which ammonia could precipitate nothing further, was assayed with carbonat of soda, which separated a white matter, which was increased by boiling the fluid, even to dryness. It consisted of carbonat of lime and magnesia.