216 ACID1FIABLE COMBUSTIBLES. 



that it smokes violently when exposed to the air, 

 and is dissipated so speedily that it cannot be 

 weighed. But, by dropping a piece of it into a 

 known weight of water, and then determining 

 the increase of tlfe weight of the liquid, I was 

 enabled (by throwing down the acid by means of 

 muriate of barytes) to show that, when solid, 

 it consists of pure acid, totally destitute of water. 

 I have obtained it crystallized in flat rhomboids, 

 quite transparent, the large faces deviating only 

 a few degrees from 90. 



It is converted into vapour at a temperature 

 which must be low, though I have not determin- 

 ed it with accuracy. The specific gravity of this 

 vapour is 2*7777> that of common air being 

 unity. One volume of it is capable of uniting 

 with, and condensing, just 2 volumes of ammo- 

 niacal gas. A volume, therefore, is equivalent 

 to an atom of the acid, for 2 volumes of ammo- 

 niacal gas are just equivalent to 1 atom of am- 

 monia. 



II. Let us now determine the atomic weight 

 of sulphurous acid. 



1. This acid contains less oxygen than sul- 



tion oi sul- 

 phurous phuric ; for when the alkaline sulphites are dis- 

 solved in water, they are gradually changed into 

 sulphates, while at the same time a quantity of 

 oxygen gas is absorbed. Its atomic weight, 

 then, is less than that of sulphuric acid. 



2. Sulphurous acid is a gaseous compound, 



