160 Report on the Soda Soils of the Barramahai. [No. 110.. 



soil is sandy and incapable of supporting vegetation, no herb growing on 

 them, but a scanty scrubby grass. In general they lay upon a bed of 

 Kunkur, which is sometimes, as near Paulcode, of considerable depth. 



These beds of soda soil are well known to the natives, who call them 

 in Tamul, Chour Munno— -and extract the soda for the purpose of fluxing 

 powdered white quartz to make bangles with. The Dhobees also collect 

 the earth, and by lixivating it make a solution of soda which they use in 

 washing clothes by adding quick lime, to make the solution caustic. But 

 so ignorant are they in general of the principle of the mode of use, that 

 they often convey the earth sometimes fifty miles, not being aware that 

 the labour of carriage might be decreased by extracting the salt. 



The Bangle makers extract the impure soda by mixing the earth with 

 water in a pit, and allowing it to settle, the solution is then drawn off, 

 and evaporated by sprinkling it on cowdung spread upon the surface of a 

 granite rock. When the cake has become about half an inch in thick- 

 ness, it is taken off and is broken into pieces, in which state it is called 

 Chour Billah and is stored in houses for use, sometimes to the amount of 

 400 maunds. 



The Chour Billah is sold at the rate of 17 i Rupees per ton, and con- 

 tains 23 per cent, of insoluble matter, the soluble part being in greatest 

 part all carbonate of soda with a little vegetable and extractive matter, 

 and some muriate and sulphate of soda in small quantity. A solution of 

 it will not crystallize in consequence of the extractive matter, and the 

 natives are quite ignorant of the mode of crystallizing it, and do not 

 even know that it contains a salt. 



In Bengal soda soils are also found, but according to Dr. O'Shaughnessy,. 

 (Manual of Chemistry, page 227) it contains 15 per cent, of sulphate of 

 soda, which salt being more soluble in hot than cold water cannot be se- 

 parated by crystallization from the carbonate, and the product of these 

 soils in Bengal cannot therefore be applied to any useful purpose unless 

 the very expensive process of decomposing the sulphate by fusion in a 

 furnace is resorted to. 



Being engaged in an extensive chemical examination of the minerals 

 of this district in which pure carbonate of soda is required in consider- 

 able quantity as a flux, and as the price of the salt as vended in retail at 

 Madras is very great, it has occurred to me to endeavour to supply the 

 want from the mineral resources of the country. 



I have found by experiment that a very pure carbonate of soda may be 

 separated from the crude soda, which the soils of Barramahal yield by 

 simply charring the Chour Billah, or the residue, after evaporating to dry- 



