FLUOSILICIC ACID. 175 



of it at the temperature of 60, and when the 

 barometer stands at 30 inches, weigh 110*1385 

 grains. 



When this gas is placed in contact with liquid 

 ammonia it is rapidly absorbed, while the silica 

 which it contains is deposited in a gelatinous 

 state. Dr. Davy found that 40 cubic inches of 

 the gas, when thus treated, deposited 27*2 grains 

 of silica. Upon repeating the experiment, I 

 obtained 27*1 grains of silica ; but having pro- 

 cured an apparatus by which I could measure 

 the volume of the gas to within 10*00 th of a cubic 

 inch, the weight of the silica obtained from 40 

 cubic inches of the gas was 27-14 grains, or 

 more nearly 27*145 grains.* Now, the weight 

 of 40 cubic inches of this gas is 44*0554 grains. 

 Consequently, it appears from this experiment, C 



i a -,- . . 1 1 . tionoffluo- 



tnat nur-iiicic acid is a compound of silicic acid. 



Fluoric acid 1 6-9 104 or 1-25 

 Silica 27-1450 - 2-006 



44-0554 



1-25 is the atomic weight of fluoric acid, and 



* This experiment is of very difficult execution, and cost me much 

 labour and time before I was able to execute it with the requisite precision. 

 The silica is very bulky and light, and is apt to be dissolved by the water 

 employed to wash it. In consequence of this, I obtained always too little 

 silica at first, till I discovered the source of the diminution. I have omitted 

 all the unsuccessful experiments. Those given in the text I consider as 

 very near the truth 



9 



