368 T. S. Hunt on Salts from Sea-water. 
Preparation of Sulphate of Soda.—¥or this process the cold of 
autumn and winter is required. The mixtures of sea-salt and 
sulphate of magnesia, (A and B,) together with the pure sulphate 
of magnesia obtained from the mother liquors at 32°, are dis- 
solved in water heated to 95° F., with the addition of such a 
quantity of common salt as shall make the proportions of the 
two salts equal to 90 parts of chlorid of sodium to 60 of anhy- 
drous sulphate of magnesia. The warm saturated solution is 
exposed in shallow basins to a cold of 82° F., when it deposits 
120 parts of hydrated sulphate of soda, equal to 54 of anhydrous 
sulphate, or three-fourths of the sulphuric acid of the mixture. 
In theory, about equal weights of the two salts are necessary for 
their mutual decomposition, but an excess of common salt dimin- 
ishes the solubility of the sulphate of soda, and thus augments 
the product. From the residual liquid, which contains chlorid 
of magnesium mixed with common salt and a portion of sulphate 
of Menecis, the latter salts may be separated by evaporation. 
The sulphate of soda is converted into carbonate of soda by the 
usual process of calcination with carbonate of lime and coal. 
The Potash Salts——The chlorid of potassium obtained by the 
The greater yest of chlorid of potassium as yet p 
uth ‘America, is decomposed by chlorid of potassium, y rc a 
ig Sea pe 
_ Yield of the Mother Liquors.—According to a calculation © ec 
Balard the proportion of sulphates in sea-water corresponds 
