357 
on different Combinations of Fluoric Acid. 
the water in a jar over mercury, as fast as it was absorbed. 
The experiment was stopped, when the gas, after having re- 
mained in contact with the water a whole night, ceased to be 
diminished. According to this result, the proper correction 
being made for the additional pressure, water decomposes 
about 263 times its bulk of silicated fluoric acid gas. 
Dr. Priestley observed, that muriatic acid gas reproduced 
silicated fluoric gas from the crust of silex formed, when the 
latter is condensed by water.* This experiment I have re- 
peated, and as it appears to show more correctly the quantity 
of gas water can condense, I shall describe the result. 2.4 
cubic inches of muriatic gas were added to a drop of water, 
that had previously absorbed one cubic inch of silicated fluoric 
gas, in a jar over mercury. There was an immediate absorp- 
tion equal to ~ of a cubic inch. The mixture of silex and 
subsilicated fluoric acid eifervesced, and from an apparent 
solid became fluid, the whole of the silex gradually disappear- 
ing. After the first mentioned absorption, there was no far- 
ther. The gas produced was silicated, as appeared from the 
crust it deposited when removed to water, and the liquid 
formed was pure muriatic acid, for decomposed by concen- 
trated sulphuric, it afforded merely muriatic acid gas, without 
any silicated fluoric. The evident conclusion from the pre- 
ceding result is, that water condenses equal quantities of the 
muriatic and silicated fluoric acid gasses, and consequently 
that the first estimate is too low, and instead of 2 63 times its 
bulk, it is probably more correct to say that water to be satu- 
rated requires at least 365 times its volume. Neither will this 
estimate appear inconsistent with the former result, when the 
* Vide Pr’iestley on Air, Vol. II. p. 202. 
3 A 
MDCCCXII. 
