A HISTORY OF THE SODA MANUFACTURE. 



255 



on carbonate of soda, which could not have been effected without the 

 disintegration of the supposed insoluble compound. 



Assuming these views to be correct, and omitting the minor pro- 

 ducts of the black ash operation ; also assuming the decomposition of 

 the sulphate of soda and formation of carbonate to be perfect, we may- 

 form this diagram as exhibiting the reaction of the materials employed, 

 and of the products obtained : — 



MATERIALS 

 EMPLOYED. 



EQUIVALENTS. 



EQUIVALENTS. 





PRODUCT IN 

 EQUIVALENTS. 



144 of Sul- ) 





' 2 Fa 

 1 2 S 

 I 60 

 20 



2Na 



) =2XaOC0 2 



phate of > 

 Soda. ) 



2 Na 3 3 j 



20 i 

 60 



> Carbonate of 

 \ Soda. 





1 



r 2Ca 



2Ca] 



1 =2CaS 







j 1 Ca 



2 S 



Sulphide of 







2C 



; l c 



j 20 





I Calcium. 



150 of 1 





1 c a ; 



| =1 CaO 



Limestone > 



3CaOC0 2 i 



1 



Oxide of 



or Chalk. ) 







| Calcium. 







1 



[ 60 



10 C | 

 10 1 



| =10 CO 

 ► Carbonic 

 ) Oxide. 



54 Carbon 9 C 





...9 C 







In this formula I have assumed pure carbon to have been used ; also 

 that the gas evolved is entirely carbonic oxide, whilst, in fact, a large 

 proportion of carbonic acid is produced. Small coal is also used, in 

 practice, instead of pure carbon ; and it is desirable that the finished 

 black ash should contain a considerable proportion of unconsumed 

 pieces of coke ; therefore, a proportion of small coal is used in the 

 mixture, about double the quantity indicated for carbon. 



I have already referred to the presence of caustic soda in the liquors 

 obtained by the lixiviation of black ash. In the ordinary course of 

 manufacturing soda ash, as this was formerly effected, these liquors were 

 boiled down in open furnaces, and the salt obtained was roasted, so as 

 to produce a salt consisting mostly of dry carbonate of soda. During 

 these operations much of the caustic soda was converted into carbonate, 

 but the product still retained sufficient caustic to give it the objection- 

 able property of deliquescing when exposed to air. For some years 

 past the evaporation of black ash liquors has been conducted in iron 

 pans, so as to yield crystals of mono-hydrated carbonate of soda, which 

 are transferred to open furnaces to be desiccated ; also yielding residual 

 liquors containing a great part of the caustic soda originally present in 

 the black ash liquors. These residual liquors were the cause of addi- 

 tional expense to the manufacturer, and a course was pursued with 

 them which was very similar to " advancing backwards ;" inasmuch as 

 great labour and expense was applied to convert the ready-made caustic 

 into carbonate, and this product being sold to the soap manufacturer, 

 he incurred much expense to re-convert the carbonate of soda into 



