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Indiana University Studies 



process which will be discussed later. The LeBlanc Process 

 consists of treating common salt with sulphuric acid to produce 

 hydrochloric acid and acid sodium sulphate, or at higher tempera- 

 ture the normal sodium sulphate. The first reaction is as follows: 



2NaCl + H0SO4 = 2HC1 + 'Na^SO, 



This sodium sulphate is mixed with limestone and coal or 

 charcoal and calcined in a reducing flame forming a mixture of 

 calcium sulphide and carbonate of soda. This reaction takes place 

 as follows: 



Na2S04 + 2C + CaCOs = NaoCO^ + CaS + 200. 



The sodium carbonate and calcium sulphide can be readily 

 separated by leaching with moderately warm water because the 

 sulphide is practically insoluble, while the carbonate is easih^ 

 soluble. This industry has been able to hold its own with the 

 newer processes because hydrochloric acid and bleaching powder 

 are produced as by-products of the process. At least one-half 

 of the world's supply of carbonate of soda is produced by the 

 LeBlanc process at the present time. 



The manufacture of chloride of lime, or muriate of lime, 

 can be carried on along with the process of soda manufacture 

 since the only chemicals needed are limestone and weak solutions 

 of hydrochloric acid. When limestone is treated with a dilute 

 solution of hydrochloric acid and the solution concentrated by 

 evaporation and allowed to cool, crystals of lime chloride are 

 deposited. These crystals have the composition (CaCl2, 6 H2O), 

 but when they are heated they lose two-thirds of the water, 

 leaving a porous lime chloride which has a wide use as a drying 

 and dehydrating agent in chemical laboratories. At the present 

 a large supply of this compound is produced as a by-product 

 of the Solvaj^ process of soda manufacture 



Limestone in the Solvay Process of Soda Manufacture. 



The reactions of the ammonia process, later known as the Solvay 

 process, were discovered by Dyar and Hemming in 1838, but 

 no use was made of them till Solvay, a Belgian, constructed an 

 apparatus for their use in 1863. Its advantage over the LeBlanc 

 process lies in the fact that there are no troublesome by-products 

 such as ''tank waste" formed. No hydrochloric acid or chlorine 

 is formed in the process, since these all pass into the form of 

 calcium chloride. The process depends upon the fact that sodium 



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