DHOBPS EARTH is a native carbonate of soda, called sajji matti in Hindustani, and ap placaram in Tamil and Telugu. It is a whitish grey, sandy efflorescence, which often covers miles of country where decayed white granite forms the surface soil. This earth begins to accumulate in the dry weather ; immediately after the rains, it can be scraped off the surface to the depth of two or three inches and by repeated boiling and the addition of a lietle quicklime the alkali is obtained of considerable strength. IVith a little care, very clean carbonate of soda can be obtained, fit for the manufacture of toilet soap, white glass, and glazes for pottery. The Nellore, Cuddapah, Masulipatarn, and Chingleput districts yield this earth in great quantities ; and it is also found largely at Puducottah, Hyderabad, Bellary, and Mysore. The richest in alkali is from the terri tories of the Nizam, the quantity of anhydrous carbonate being about 67 per cent. Repeated attempts have been made to prepare barilla from it for exportation and very fair specimens have been exported at different times, but the moderate price of the carbonate of soda bf England, prepared from sea salt, will always prevent this from being a remunerative article of export. The coloured frits for bangle glass, in making which it is used, have lately, however, become an article of export from the Madras Presidency. It exists in immense
quantities in many parts of India, in Bengal especially, in the districts of Zfo,n,ghir, Purniah, and Cawnpur. It contains from 40 to 50 per cent. of carbonate of soda, traces of sulphate of soda, organic 'natter, clay, Band, and oxide of iron. The salt eau be extracted by washing the mineral without incineration, but the organic 'natter is dissolved at tho same time, and gives a deep brown solution, froni which pure crystals cannot bo ob tained. Firing destroy' this substance, and then the solution is colourless. But care must be taken not to push the heat beyond low redness, for the alkali at a higher temperature combines with the sand and clay, and the whole runs into green glass, insoluble in water. In Europe, barilla is pre pared either by burning seaweeds and lixiviating the ashes, the product being termed kelp and barilla, or by decomposing common salt by sulphuric acid, and then roasting the resulting sulphate with chalk, sawdust, and fragments of iron. The mass when washed gives the carbonate of soda.—Mr. IL Reynolds in Pharmaceutical Journal, 1853, xii. ; M. E. of 1855 and 1857; Betty. Phar.