16 Mr. J. Brown oJi the Products of the Soda Manufacture. 



the alkali from sulphate of soda by fusing with charcoal, and 

 digesting the fused mass in acetic acid, evaporating the acetate 

 of soda thus formed to dryness, and calcining the residue. 



Margraff" endeavoured to decompose sulphate of soda by 

 limestone, but without success. In 1768 Hagen showed that 

 salt might be decomposed by means of potash, chloride of 

 potassium and caustic soda being formed. 



Bergmann succeeded in decomposing salt by caustic barytes. 



In 1775 it was shown by Scheele that salt was partially 

 decomposed by oxide of lead. 



In 1782 Guy ton and Carny decomposed salt by fusion with 

 felspar. 



In 1781 Constantini succeeded in decomposing salt by 

 means o^ alum. 



The sulphates of lime^ magnesia, ammonia, potash, S^c. de- 

 compose salt, as also iron pyrites. 



To convert the sulphate of soda into caustic or carbonated 

 alkali was, however, the process of greatest importance. The 

 first step, viz. the conversion of soda into sulphuret of sodium, 

 was known to Glauber, Stahl, Du Hamel, Margraff and 

 others. The difficulty was to get rid of the sulphur. Du 

 Hamel effected this by means of acetic acid. But in the year 

 1784 the present process was discovered by Le Blanc and 

 Dize, and in the beginning of 1791 it was patented by Le 

 Blanc. He used carbonate of lime to convei't the sulphuret of 

 sodium into carbonate of soda. 



The proportions used by him were — 



2 parts dry sulphate of soda. 

 2 ... carbonate of lime. 

 1 ... ground charcoal. 



These were intimately mixed and introduced into a rever- 

 beratory furnace, where a strong heat was applied to it. After 

 this had been continued for about an hour, the fused mass was 

 raked out of the furnace and allowed to solidify. When this 

 cooled, it was broken up and exposed to the action of moist 

 air, which caused it to crumble down. In this way the caustic 

 soda was converted into carbonate of soda, the carbonic acid 

 being derived from the atmosphere. After being ground it 

 was ready for use. 



The soda process, as at present carried on, will be best 

 considered under the four following heads : — 



1st. The production of sulphate of soda from salt and sul- 

 phuric acid. 



2nd. The conversion of sulphate of soda into crude carbo- 

 nate of soda or British barilla. 



