Oe Se ete he SP EES ey ATE ee Fe Ch eh 
T. S. Hunt on Lime and Magnesia Salts. : 57 
although — = represented one of the neutral carbonates 
obtained by s containing three atoms of soda, eight of 
wid of = dr wa eight of water, I should prefer, padi 
farther investigation, to regard the above described substance as 
and magnesia. It is worthy of note that while the simple 
carbonate of magnesia retains in crystallizing 6HO, the com- 
pound of one equivalent each of lime and magnesia contains 
only 5HO, and the last, in which the lime predominates, is much 
less hydrated. These double carbonates deserve a more careful 
ditions analogous to the double carbonates of lime and mag- 
nesia just described. The amorphous paste obtained by mix- 
ing a solution of sulphate of magnesia with a slight excess of 
carbonate of soda undergoes a change precisely similar to that 
of the mixed carbonates, and is transformed into small prisms 
aggregated into spherical masses, like the double carbonates of 
lime and magnesia. It is tolerably permanent in the air, and 
yielded me 29:0 per cent of magnesia; which exactly corres- 
ponds with the above formula 
Supersaturated solutions of carbonates of lime and magnesia. 
§ 88. In $78 allusion was made to om coed experiments on 
the solubility of carbonate of lime in presence of an excess of 
carbonic aci ound that by the addition of re oghiag ag of 
soda to a solution holding chlorids of sodium, calcium - 
nesium (with or without sulphate of soda), and saariited with 
carbonic acid, it is possible to obtain transparent solutions hold- 
ing from 3-40 to 416 gr. of carbonate of lime to the liter. Of 
of lime which water is capable of holding permanenily in solu- 
tion; although, as pointed out in §56 of my recent paper on 
a Waters (this —* Ae xl, 196), it would seem from 
mparative experiments f Boutron and Boudet that these 
chlorids favor the formation of unstable supersaturated solutions. 
89. have now to speak of supersaturated solutions of 
carbonates of lime and magnesia without any excess of carbonic 
acid, of which a brief notice is given in the section of that paper 
an. Jour. Sci1.—Seconp Serres, Vou. XLII, No. 124.—Juxy, 1866, 
8 
