62 T. S. Hunt on Lime and Magnesia Salts. 
found in solution. The residue was then farther digested for 
the same time with 250 c.c. of a solution of gypsum satura 
with carbonic acid, and gave a farther amount of sulphate equal 
to 0.052 gr. carbonate of magnesia. That the first action of the 
g n a hydrous carbonate appears from the fact 
that the residue from the above processes, when farther digested 
for ten days in the cold with a fresh portion of pure gypsum so- 
lution and ers caeeres. agitated, gave only traces of sulphate of 
magnesia. 
°100. It was, haieova, possible that besides hydrous a 
ate of magnesia an admixture of hydrate of magnesia might 
also in some cases intervene to effect the decomposition of gyp- 
sum. The native crystalline hydrate, brucite, in presence of a 
—_ of gypsum containing carbonic acid readily gives rise 
ulphate of —— and the rock known as + sae is 
ka at 15° C. took up from the mineral 8-95 p. c. of magnesia 
and 0:30 p.c. of lime. 100 gr. of ate: and carefully 
washed predazzite and 1:0 gr. of gypsum were digested for five 
days with 250 c.c. of water at 15°-18° C., snd the tiquid’* then 
bly in the cold, aia a ae acetic acid was employed for its analysis. The two 
spec imens gave as fi 
. 
Carbonate of — 364 367 = 593 P. ¢. 
magnesia, 25°9 25:2 = 40°7 
302 
Inso. tu ble, 
Water, alumina and loss, 17°6 
1000 ig 0 
m 
wit any einarveeceis ast and gave ‘a8 aout aaa 53-2, alumina and 
cules iron-oxyd 19-5, magnesia a trace, water and loss 17:0, insoluble 
41=1 ats This clay See ae. Neg oe argillites which I have de- 
seri the Geology vd Canada, page 601, a portion of a magnesian silicate, 
which nin either exist asa double silicate with alumina analogous to chlorite, or 
as a simple hydrous ete: like the sepiolite or magnesian marl which is com 
gypsum inly lamina ted and enclose allie of menilite. It efferv 
pala cold acai is da pete ig mi it _ fps cent of carbonate of lime, siphare 
The’ analysis gave silica 58°4, m slong 20°9, li ren a trac igen and i 
3-0, volatile 17:0==99°3. This silicate is readily sisiosivacal by sulphuric acid, eve 
after ignition. In my paper on Natural Walkers, tl this Journal, : xl, 49, will be 
found some observations on the artificial fo a (8 a, subject 
which I edt Ness to discuss in a separate paper. 
