and the formation of Gypsum and Magnesian Rocks. 181 
of magnesia, equal to 8°63 p.c. of dolomite, oonmey oe 43°5 p.c. 
of magnesian carbonate). At a temperature of 60° F., the same 
acid caused a slow but continued lancaatiaans of gas bubbles 
from the powdered dolomite, which after 30 hours lost 28-0 p. c. 
of its weight, the dissolved portion containing 45°0 p. c. of car- 
bonate of magnesia. At 120° F. the action of the acid upon the 
powdered dolomite was Be with gentle effervescence, 
and the amount dissolved after two hours digestion, was 13° 6 
per cent. 
A white crystalline aly from Styria, whose only impu- 
rity was a portion of carbonate of iron “ae ual to 0°9 p. c. of per- 
oxyd, and which was slowly but completely soluble in hot hy- 
drochloric acid, was also slightly attacked by dilute acetic acid 
at 60° F.; after twelve hours digestion there were dissolved 0°63 
‘ c. of the carbonate. At 125° F. however a distinct efferves- 
cence was produced with the acid, and “ the end of three hours 
11-0 p. c. of the magnesite were dissolv 
From these experiments it was evident that although not insol- 
uble in acetic acid of 15-0 p.c. at 82° F., this liquid might serve 
to separate dolomite from carbonate of lime, and also at a higher 
maperere to effect a partial separation of dolomite from mag- 
“30, “The insolubility of the acca ne ser of lime and 
magnesia in carbonic acid water important fact in the 
history of dolomite. Bischof Suns eur on the prolonged action 
of a solution of carbonic acid upon a limestone containing 11°54 
p. c. of magnesian carbonate, anees were dissolved 4:29 p. c. 
Achsonte of lime and not a trace of nh EVES In like manner - 
& manganesian iron-spar, which contained 14:0 p. c. of carbonate 
of lime and 15:0 p. ¢. of carbonate of magnesia, gave to carbonic 
acid water four parts of carbonate of lime for one part of magne- 
~ ee onaie —(Lehrbuch, ii, 1176. 
1. Accepting the idea that dolomites have been formed by 
the e alteration of beds of carbonate of lime, hail long 
Suggested that a solution of sulphate of magnesia at 
gh. temperature might produce this change, giving rise ee 
deable decom: sition to. carbonate of magnesia 8 and s ues of 
ha:iectee:to- bate , regarded as forming with the excess 
of carbonate of lime a double earbonate—(Liebig and Kopp, 
