106 On the Extraction of Salts from Sea-Water. 



has led the manufacturers of alum to replace this alkali wholly 

 or in part hy ammonia, hut the potash salts from sea-water will 

 furnish potash so cheaply as to render the use of ammonia no 

 longer advantageous. 



The greater part of chloric! of potassium as yet produced in the 

 salines in the south of France is now however, employed chiefly 

 in the Imperial manufactories of saltpetre or nitrate of potash. 

 The nitrate of soda which is so abundant in some parts of South 

 America, is decomposed by chlorid of potassium, yielding com- 

 mon salt, and pure nitrate of potash for the fabrication of gun- 

 powder. 



Yield of the Mother Liquors. — According to a calculation of 

 Mr. Balard the proportion of sulphate in sea-water corresponds to 

 a quantity of anhydrous sulphate of soda equal to one-eighth that 

 of the common salt, but on a large scale the whole of this cannot 

 be economically extracted ; the saline of Baynas yields annually 

 besides 20,000 tons of sea-salt, 1550 tons of dried sulphate of 

 soda, or 7 - 75 per cent., instead of the 12*50 per cent, indicated by 

 theory. Estimating the yield at 7-0 per cent, according to Payen, 

 the cost of the sulphate will be 30 francs the ton, which will make 

 the cost of the crude carbonate of soda 50 francs, while it brings 

 in France from 80 to 120 francs the ton. 



The amount of chlorid of potassium obtained is equal to one- 

 hundredth, or to 200 tons for the above amount of sea-salt, and 

 the value of this salt is 360 francs the ton. By its decomposition 

 it will yield 185 of pure carbonate of potash, which sells for 1000 

 or 1100 francs the ton. Thus it appears that for 20,000 tons of 

 sea-salt, worth at 10 francs the ton, 200,000 francs, there is ob- 

 tained chlorid of potassium for the value of 72,000 francs. The 

 potash being a secondary product from the residues of the pro- 

 cesses for sea-salt and sulphate of soda, is obtained almost with- 

 out additional cost. It has been shown by careful calculations 

 that the sulphate of soda and the potash from the waters of the 

 Mediterranean, will alone repay the expense of extraction, the 

 sea-salt first deposited, being re-dissolved and carried back to the 

 ocean. A powerful company is now erecting works on a great 

 scale in the vicinity of Marseilles, where the marshes of the Ca- 

 margue offer a great extent of waste lands, valueless for cultiva- 

 tion, but well adapted for this manufacture. Here it is proposed 

 to evaporate the sea-water solely for the sake of the sulphates, 

 the potash and the magnesia which it contains. Basins which are 



