20 Mr. J. Brown on the Products of the Soda Manufacture. 



Per 1000 grs. 

 200 grs. of sulphate of soda lost 1*70 8*50 grs. free acid. 



1-84. 9-20 



Average 8*85 



Composition of Crude Sulphate of Soda. 



Sulphate of soda . 

 Sulphate of lime 

 Sulphate of magnesia 

 Chloride of sodium 

 Iron peroxide . . 



Sand 



Free acid . . . 



962-170 

 9-731 

 2-893 

 10-956 

 2-300 

 3-100 

 8-850 



1000000 



II. This brings us to the consideration of the second part of 

 the process, namely, — the conversion of sulphate of soda into 

 crude carbonate of soda or British barilla. 



This is effected by the combined action of coal and carbo- 

 nate of lime. The following table shows the proportions 

 commonly used : — 



These, after being intimately mixed, are introduced into a 

 reverberatory furnace and strongly heated. The mass soon 

 becomes soft, when care must be taken to stir it frequently in 

 order to expose a fresh surface to the heat. When it becomes 

 of the consistence of dough the chemical action commences, and 

 jets of inflamed carbonic oxide begin to issue from it. The 

 evolution of gas soon becomes very rapid, so much so, that 

 the whole mass appears to be in a state of ebullition. When 

 this ceases the operation is completed, and the fused mass is 

 raked out of the furnace and allowed to solidify. The cake 

 thus obtained is the crude carbonate of soda, or, as it is tech- 

 nically called, " soda ball " or " black ash." 



This process consists of two subprocesses, which might be 

 carried on in separate furnaces. 1. The coal is consumed at 

 the expense of the oxygen of the sulphate of soda, causing the 

 formation of sulphuret of sodium and carbonic oxide — 



NaO, S03 + 4C=NaS + 4CO. 



2. The sulphuret of sodium thus formed is decomposed by 



