1888.] Mr A. Johnstone on Carhonic Acid Water. 
439 
procured a decided residue, which after chemical examination I 
found to be almost entirely magnesium carbonate ; there was, how- 
ever, a trace but only a trace oi ferrous carbonate. 
In order to make certain that the solvent action was due to the 
presence of the carbonic gas in the water, I allowed a litre of 
carefully distilled water to act for two months on the same weight 
of the same variety of olivine crystals which I had used in the above 
experiment, and at the expiration of that time I tested a portion of 
the li(|uid by the methods already stated for magnesia and iron ; I 
could not detect even the faintest trace of those substances, and 
after evaporating the rest of the liquid to dryness, I was equally 
unsuccessful — observing no indication of any residue whatever. 
I analysed a variety of practically fresh olivine similar to that 
taken for the above experimental investigation, and I also submitted 
to analysis the crystals of olivine which had been subjected to the 
action of the carbonic acid water as described. The two analyses I 
give below : — 
I. Analysis of practically Fresh Olivine. 
Silica, 
41*25 ] 
Magnesia, 
50*74 
Protoxide of 
Alumina, 
Calcium, 
Manganese, 
iron, 
1 
j 
7*88 
. Traces 
Nickel ^ 
Chromium, 
J 
Total, 
99'87 per cent. 
II. Analysis of Olivine (originally of the same quantitative composi- 
tion as I.) which had lam for two months in distilled ivaier 
saturated with carbonic acid, gas : — 
Silica, . ■ . . 41*989 per cent. 
Magnesia, . . . 50*008 ,, 
Protoxide of iron, and ( 
Ferric Oxide, j < ^ 
Total, 99*876 per cent. 
When the olivine crystals were removed from the liquid their 
physical characters were observed to have changed slightly. 
Originally of a pale olive-green colour, and transparent to semi- 
