354 Mr. J. Davy’s Account of some Experiments 
destroyed; and a much larger quantity of gas is procured 
from the same materials, and with less trouble and less heat ; 
the action indeed at first is so powerful, that gas begins to 
come over before the application of heat is made, and a very 
gentle one only is required to continue its production. 
Previous to its analysis, it was necessary to ascertain the 
specific gravity of the gas. This I have endeavoured to do. 
The gas, the subject of experiment, was quite pure, being to- 
tally condensed by water. A Florence flask was exhausted ; 
in this state, weighed by a very delicate balance, it was 
= 1452.2 grains. 
Filled with common air - = 1452.2 -j- 10.2 
Again exhausted - = 1452.2 
Filled with silicated fluoric gas = 1452.2 + 36.45 
Hence as 10.2 : 31 : : 36.45 : : 110.78. 
Thus it appears, that 100 cubic inches of silicated fluoric acid 
gas, at ordinary temperature and pressure, are equal to 110.78 
grains. 
When silicated fluoric acid gas is condensed by water, it is 
well known that part only of the silex is deposited. To ob- 
tain the whole, in order to ascertain the proportion in the gas, 
I have employed ammonia in excess. 40 cubic inches of the 
gas (barom. 30, therm. 60) were transferred in portions of 
10 cubic inches, at a time to a solution of ammonia. The silex 
precipitated was carefully collected on a filter, and washed 
till the water that passed through it, ceased to be affected by 
nitrat of lime. It was next dried, and strongly heated in a 
platina crucible. It weighed 27.2 grains, and was pure silex. 
Supposing fluoric acid to be the remaining 17.1 grains, which 
added to 27.2 grains are equivalent to the weight of 40 cubic 
