on different Combinations of Fluoric Acid. 355 
inches of the gas, it appears that 100 parts by weight of this 
gas consist of 
O 
6 1.4 silex 
38.6 fluoric acid 
100.0 
That this estimate may be correct, it is evident, that am- 
monia should have the property of precipitating the whole of 
the silex of silicated fluoric gas ; which I shall not now en- 
deavour to prove, but leave it to be considered in another 
part of the paper. 
There is no improbability attached to the idea, that silicated 
fluoric acid gas may, from the manner in which it is prepared, 
contain a proportion of alkali. To discover whether this was 
the case, a solution of nitrat of lime was added to the ammo- 
nia cal solution neutralized by nitric acid, from which the silex 
in the preceding experiment had been removed. The preci- 
pitate of fluat of lime was separated by filtration. The filtered 
liquid was evaporated to dryness ; and the ammoniacal salt 
heated in a platina crucible till it was entirely dissipated. The 
residue had the appearance and taste of quick lime. It w 7 as 
dissolved in acetic acid, and the solution yielded sulphat of 
lime on the addition of sulphat of ammonia. The liquid was 
evaporated to dryness, and when the residuum had been 
heated to dull redness, nothing remained but a little white 
powder, weighing about a grain, and having all the properties 
of gypsum. Thus it appears that silicated fluoric acid gas 
contains no alkali. 
My next object was to ascertain the composition of common 
liquid fluoric acid — that acid obtained by the decomposition of 
