T. S. Hunt on the Chemistry of Natural Waters. 187 
the greater portion of the chlorid of sodium crystallizes out in 
anearly pure state. ‘The mother-liquor of specific gravity 1-24, 
having lost about four-fifths of its chlorid of sodium, still con- 
y 
phate of magnesia and chlorid of sodium of the or een to 
phates may be separated in this form from the mother-liquor of 
124, previously diluted with one-tenth of water; without which 
addition a mixture of hydrated chlorid of sodium would sepa- 
Tate at the same time. If, on the other hand, the temperature of 
the mixed solution be raised above 50° C., the sulphate of soda 
crystallizes out in the anhydrous form, as thenardite. By the 
Spontaneous evaporation during the heats of summer of the 
mother-liquors of density 1:35, a double sulphate of potassium 
and magnesium separates. These reactions are taken advantage 
of on a great scale in Balard’s process, as modified by Merle,” 
for extracting salts from sea-water. 
23. The results of the evaporation of sea-water would how- 
ever be widely different if an excess of lime-salts were present. 
Tn this case the whole of the sulphates present would be depos- 
ited in the form of gypsum at an early stage of the evaporation, 
and the mother-liquor after the separation of the greater part of 
the common salt, would contain little else than the chlorids of 
Sodium, potassium, calcium, and magnesium. : ; 
~ $24. A consideration of the conditions of the ocean in earlier 
arte age double chlorid of potassium and magnesium (erpad of rock ealt 100 
feet thick, at Stassfurth in Prussia. It is associated with considerable quantities of 
te of magnesia, According to Clemm this sulphate of magnesia, to whi 
Es 
r 
oe 
= 
z. 
2 
= 
te 
Ss 
= 
o 
co 
e 
2 
- 
= 
ae 
& 
& 
5 
ce 
a 
3 
> 
7 
= 
in a current of steam, the acid assing off undecompose it is 
beac} took quantities as to be of economic importance. (Bull. Soc. Chim. de 
aris, + Pp. 297, : 
bites’? MY Paper in this Journal, [2], xxv, 361 ; also Report of Juries of the Ex- 
of 1862, class I, p. 48. 
