SA Te OS Le CREE Mena EEN FTAA eM VON eee ney hg See Ree ye CREE EE TLS 
T. S. Hunt on Lime and Magnesia Salts. 61 
days, when the filtrate, freed from gypsum by evaporation and 
the addition of alcohol, gave no trace of magnesia. The resi- 
due was then treated for the same time with water holding car- 
bonie acid in solution, and the filtrate having been evaporat 
to dryness, gave to water an amount of sulphate corresponding 
to a 0 of carbonate of magnesia for the 200 ¢.c., equal to 
rssath of the weight of the dolomite. The digestion of a simi- 
lar iS of dolomite and gypsum with pure water — r six 
days at from 50° to 60° C., with frequent agitation, gave no appre- 
— amount of soluble magnesian salt. When lesadiesade dol- 
mite was digested at this temperature with a solution of pate 
of calcium for twenty-four hours, an amount of chlori mag- 
nesium equal to ;4;;ths of the dolomite was formed. 
It was evident from these and similar experiments that no re- 
nmi puey place between dolomite and solutions of gypsum 
ev ° C., except in the presence of carbonic acid, whose 
renee ation on pocerae ($79) causes the formation of a small 
amount of s e of magnesia. It was then necessary to 
search stools for an explanation of the origin of the magne- 
sian sulphate found in the conditions observed by Haidinger 
and Suckow. 
- 98. The hydrous aoe e magnesia are — attncla 
sulphate of magnesia when digested for twelve hours in the 
cold with a solution of gypsum, This hydrated carbonate also 
completely decomposes protosulphate of iron in the cold. 
bsence of any hydrous carbonate of magnesia from 
the Galt dolomite was i by its complete indifference to the 
action of gypsum solutions. It was, however, possible that some 
other dolomites might contain portions of such a carbonate inter- 
mixed. Accordingly a white earthy magnesian limestone from 
Chaumont,’ belonging to the gy psiferous series of the Paris 
basin, was selected for experiment, pulverized, washed and dried. 
Of this 100 gr. were digested for six days with 1-0 gr. of gyp- 
sum and 250 c.e. of water at from 15°-18° C. At the end of 
this time sulphate of magnesia equal to 0 025 of carbonate was 
* Ina note published in 1860 in this Journal, [2], xxix, 284, I showed for the 
first eine that the gypsum of the basin of Paris, France, is immediately overlaid 
by dolomite. fi was there stated that two specimens of the so-called white marls 
