T. S. Hunt on Lime and Magnesia Salts. 65 
carbonates would yield dolomite by ee ae For this pur- 
se a portion of the hydr®carbonate formed at the ordinary 
of iene acid of three per cent, by which it was at first en 
attacked. The last or fourth part was not perceptibly ac 
upon by cold dilute hydrochloric acid, but required heat and 
long digestion with this acid to effect its solution. The compo- 
sition of the successive portions was as follows: 
Calc. Carb. Mag. Carb. 
i, 21 parts, 90°36 9°64 
II. A ES ls 99°06 “94 
UI 20... St 82:09 17-91... 
IV. i aaehes 9°52 90°48 
These results show that as in the preceding section but little 
SO is formed, though the proportion of lime which still 
remains in Iv, 1 indicates a certain amount of the double salt. 
The presence of nearly ten per cent of magnesian aren (in 
with less ons one per cent in II, seems to be due toa partial 
decomposition of the magnesian carbonate during its dehydra- . 
tion, involving a loss of carbonic acid and the formation of 
hydrate of magnesia. A similar result is seen in the second ex- 
perumpens of the last section, while in the previous experiment 
is was to a mete extent prevented by the presence of bicar- 
bonate of 
§ 106. A neon of the hydrocarbonate with excess of lime- 
salt, described in n § 86, gave, when treated like the last, a some- 
what larger admixture of dolomite and when the hydrous double 
0°-9 
carbonate formed at 8 0° C. was gradually heated with water 
to 180° C., the fractional analysis of F the product showed that a 
large proportion of dolomite had oma on rmed. The composi- 
tion of the first and rong rtions follows, the second 
having been lest, and the third completely ani ed, 
Carb. Cal. Carb. Mag. 
i. 25 parts, 583 41°7 
i. PE AP undet. undet. 
Ill. va 46°5 53°5 
$107. In another trial with a granular double carbonate pre- 
pared at about 60° C., and then heated as before, the following 
results were wie 2 fractional analysis, a residue of pure 
ae of magnesia insoluble in acetic acid remaining. 
Carb. 
Calc, Carb. Mag. 
ce 66°7 33°3 
II. 55:4 44°6 
00°0 100°0 
It suffices to cahper the last two results with those o ot in 
Am. Jour. Sc1.—Srconp Series, Vou. XLII, No. 124.—Jury, 1866. 
9 
