BY DOLOMIEU.
199
and untainted with inflammable matter. And the process was twice
performed with this crystal : The firſt time the heat was not raised so
high as to bring over the third product of gases, but the second was
completed. The residuum in the retorts, after the first and last ex
periment, was a white, vitrified, opaque, blown-up matter; that of the
second experiment was perfectly vitrified, and proved a greenish glass.
But all these three were very diffolvable and even deliquescent; and
were diffolved by water into a liquor silicum, which by rest deposited
a fuliginous-like matter.
8. The author is of opinion that the inflammable and azotic gas
come from the quartz, for these reasons : 1/, The alkali is not decom
pounded or destroyed, but can be separated again entire from the
silica by acids. But the quartz is certainly very much changed, for
it is become soluble in all the acids, even the acetous, provided these
are added in a fufficient quantity as soon as it is precipitated from the
liquor silicum. The sulphuric acid sometimes redissolves it so quickly
that the precipitation or separation of it from the alkali is not percept
ible ; and the same thing happens with any other acid, if the solution
of the liquor filicum be largely diluted. That there is a real solution
hére by the acid, becomes evident when we add enough of alkali to
saturate the acid, for then the filiceous earth is precipitated again,
especially when the alkali we uſe is a mild alkali, and moſt certainly
if the volatile alkali. For if we uſe a cauſtic alkali, it is necessary to
take care that no more be added than just enough. A little superfluity
of it redifsolves the silica very quickly again; and thus it can be
redissolved by acid or alkali as often as we please.
The author believes that the inflammable and phlogisticated airs
come from the quartz; and that the boiling and blowing of it up in
to a spongy glaſs, when it is melted by the heat of vital air, is occa
sioned by the extrication of those airs from it; that the fire or light,
and the smell of burnt air, produced by striking pieces of quartz against
one another, are to be imputed to the bases of thoſe airs in its compo¬