FLUOBORIC ACID. 179 



very tedious, and the quantity of gas obtained 

 but small. 



The specific gravity of this gas was found by Specific 

 Dr. Davy to be 2-3709- I took its specific^ 

 gravity two different times with great care, and 

 obtained 2'3984. This, as will appear immedi- 

 ately, exceeds the theoretical specific gravity by 

 a quantity rather too great to be ascribed to 

 error in experimenting. I was long unable to 

 account for this difference ; I could perceive no 

 mistake in the process, and a repetition of it 

 gave me almost exactly the same result. I found 

 that the gas contained a slight mixture of fluo- 

 silicic acid gas. The volume of this being de- 

 termined, and allowed for, reduced the specific 

 gravity of fluoboric acid gas to 2'38833, which is 

 still above the theoretical gravity. At last I 

 discovered that this gas carries along with it a 

 little sulphuric acid, which, of course, increases 

 its gravity somewhat. According to the most 

 accurate experiments which I could make, 100 

 cubic inches of the fluoboric acid gas which I 

 examined, contained about 0'8 grain of sulphu- 

 ric acid. Now, if from 7^*844 grains, which I 

 found to be the weight of 100 cubic inches of 

 this gas, we subtract 0'8, there will remain 72*044 

 grains for the true weight of fluoboric acid gas. 

 This will make its specific gravity 2 '3622. Now, 

 we shall see immediately, that the theoretical 

 specific gravity, which undoubtedly must be ex- 



M * 



