214 ACIDIFIABLE COMBUSTIBLES. 



Formation 1 atom sulphuric acid = 5 



l atom protoxide of iron = 4-5 

 7 atoms water . = 7'875 



17-375 



So that an integrant particle of it weighs 17*375, 

 and 4 integrant particles weigh 69*5 parts. If 

 we expose 69*5 parts of this salt to a sufficient 

 heat, it becomes white and loses 30*375 parts of 

 water. Now, the whole water contained in 69*5 

 parts of this salt is obviously 31 '5 parts ; conse- 

 quently, there still remains 1*125 parts of water 

 united to the salt ; and the salt thus heated is a 

 compound of 



4 atoms sulphuric acid = 20 

 4 atoms protoxide of iron =18 

 1 atom water . . =1-125 



39-125 



When these 39*125 parts are put into an earthen- 

 ware retort, and exposed to a strong heat, one 

 half of the sulphuric acid, amounting to 10 

 parts, is decomposed into 8 parts of sulphurous 

 acid, which flies off and is dissipated, and 2 parts 

 of oxygen, which, uniting to the 18 parts of pro- 

 toxide of iron, convert them into 20 parts of 

 peroxide of iron. The remaining 10 parts of 

 the sulphuric acid pass over into the receiver 

 united to the 1-125 of water. 



This is the process followed aj; Nordhausen in 



