288 spina Intelligence. 
quartz, but on repeating the treatment of the same quartz with a second 
portion of the apn re only ‘35 per cent was dissolved. The object of 
this process was to r move any soluble silica, and the quartz thus purified 
was employed Sy thie following experiments, which were performed in a 
vessel of platinu 
I. 1000 parts of quartz and 200 of carbonate of soda were boiled with 
water for ten hours, and the mixture was several times evaporated to dry- 
ness, and exposed for a few minutes to a temperature of about 300° F, 
The amount of silica taken into solution was 12 parts. 
drocarbonate of magnesia was prepared by mingling boiling 
solutions of sulphate o of magnesia and carbonate of potash, the latter in 
excess ; the precipitate was washed by boiling with successive portions of - 
water. 1000 parts of quartz were mixed with about as pos of this 
magnesian carbonate and boiled as above for ten lou cess ’ 
a 
hydrochloric acid was then added, the whole evaporated to dr #2 oat 
e magnesian salt washed out with dilute acid. The residue was then 
boiled for a few minutes with carbonate of soda, and gave 33 parts 
soluble silica. 
IIL. A mixture of 1000 da of quartz, 200 of carbonate of soda with 
water, and an excess of carbonate of magnesia was boiled for ten hours, 
and the residue, treated as in the is experiment, gave 148 parts of solu- 
ble silica. The alkaline liquid contained a little magnesia, but no silica 
in solution. That the soluble silica was really combined with magnesia 
was shown by boiling the insoluble mixture with sal-ammoniac, which, 
dissolving the carbonate, left a large amount of magnesia with the silica. 
This silicate was readily decomposed by hydrochloric acid, the greater 
part of the silica separating in a pulverulent form 
The third experiment was suggested by some observations on the bie 
tions a silicate of soda with earthy carbonates. Kuhlmann has remar 
the power of carbonate of lime to abstract the silica from a boiling see 
tion of soluble glass,* and it is known that chee exerts & — 
ae ion. I have found that when artificial carbonat magnesia in a 
Is boiled with a solution of silicate - —s the batter’ js completely ae 
wet soda, and a silicate hier” 
result, If we boil for some pay a mixture of. sgnived “silic 
from the decomposition of a silicate by an acid (and edi “A 
oni In all alkaline carbonates), with a small portion peer a dente 
and an excess of hydrocarbonate of magnesia, we obt oe y be | 
. a 
powder which contains all the silica united with magnesia, and peer 
iled with carbonate of soda and er nae without decompo 4 
aie may be : 
It is obvious from the above experiments that ped res éit rs! doubt- 
tained with quartz, although the process is much slo 
ess be accelerated under | pressure at a somewhat atin ated tem 
which would dediana the solvent power of the alkaline restate 
her® 
Comptes Rendus de l’Acad. des Sciences, Dec. 8rd and Dee. se 1855, W 
will be found many important observations on the alkaline si 
t Reports of the Geol. Surrey o of Canada, 1851-53-54. 
