ACIDIFIABLE COMBUSTIBLES. 



crystals, which fall into the water at the bottom 

 of the chamber. The moment they come in 

 contact with that liquid, a decomposition takes 

 place; the sulphurous acid is converted into 

 sulphuric acid, and the nitrous acid into deutox- 

 ide of azote. This last substance makes its es- 

 cape in the gaseous state ; but immediately comes 

 in contact with the common air of the chamber, 

 and is converted into nitrous acid, which, unit- 

 ing with a new dose of sulphurous acid, falls 

 again into the water. These decompositions 

 and new formations continually go on as long as 

 the air of the chamber contains oxygen gas and 

 sulphurous acid. The water, when sufficiently 

 impregnated with sulphuric acid, is drawn off 

 from the bottom of the chamber, and concen- 

 trated as far as possible in leaden boilers. It is 

 then put into glass or platinum retorts, and kept 

 in a heat of at least 600, till as much concentrat- 

 ed as possible.* 



tioTofihe Acid, thus prepared, is a clear, transparent, 

 acid ot colourless liquid like water, with a certain degree 

 of consistency, so as to adhere to the sides of a 



* The acidulous water, when taken out of the leaden chambers, has a 

 specific gravity of about 1-22. It is a compound of about 1 atom sulphu- 

 ric acid, and 15 atoms water. Jt is concentrated in the leaden boilers till 

 its specific gravity becomes 1 '75. In this state it is nearly a compound of 

 1 atom acid, and 2 atoms water ; the boiling point of acid of this strength 

 is 4-35. Beyond this strength it cannot be conveniently carried in leaden 

 vessels, because its corroding action on the lead increases at a great rate as 

 the boiling point rises. 



9 



commerce. 



