C. A. Goessmann on the Onondaga Mineral Springs. 217 
I. How does carbonate of magnesia act yin sulphate of lime in 
the presence of free carbonic acid ?—To test the degree of this ac- 
tion, I adopted the ipl course. T mixed in a suitable 
vessel ten grams of well washed carbonate of magnesia, twenty- 
five grams of sulphate of jeer (gypsum,) and five hundred 
cubic centimeters of distilled water : which mixture I afterwards 
treated for a short time each day during four weeks, with well 
washed carbonic acid gas, soas to secure a constant supply of 
bicarbonate of magnesia to the solution of gypsum. The solu- 
tion thence resulting, after being separated by filtration from 
the white residue, was equal to four hundred and fifty cubic 
centimeters. I place ced it in a flat glass dish, and left it to grad- 
ual Phd aecpae at the ordinary temperature. 
few days rest the bottom of the vessel began to be 
covered with a small amount of sediment. No further note- 
worthy change took place, until the whole liquid gradually 
formed into a solid crystalline mass, consisting in the main of a 
net-work of needles. The solution, being tested before its so- 
lidification, was of a slightly alkaline reaction; the crystals re- 
sulting from. its evaporation were transparent, a crumbled 
readily to a white powder when exposed to dry 
One hundred parts of an apparently sidered aiuls of the 
saline mass, contained— 
Carbonic acid, - . - 16721 
Sulphuric acid, - - 31°4803 
Calcium oxyd (lim e), - - 0°7988 
Magnesium oxyd (magnesia), - 17-0327 
One hundred parts of the same mass, heated to a dull red 
heat, lost 51:0593 parts of its weight; leaving therefore 48-9407 _ 
parts of a white residue. 
abe of lime, . 1°4268 
¢ hydrated pa aires of magne 
“3(Mg0, CO?)-++-(Mg0, HO), 2°4911 
Sulphate of magnesia (MgO, 03-4710), 96°8020 
As the oe amount of the saline compound obtained in the 
t d 
progress its co. noentration as carbonate of pee The ap- 
parently slow decomposition of gypsum must be attributed to 
the limited solubility of that compound. It is not uareasonable 
