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37° ]
In this manner I have found that
the white zeolite defcribed above,
contains 48 in 100 o f Iiliceous earth,
22 of pure argillaceous earth, and
from 12 to 14 of calcareous earth. I f
thefe numbers are added together,
and reckoned with what it contains of
water, the produce is fomething more
than 100. This furplus proceeds
from the calcareous earth that enters
into the zeolite without fixed air, with
which it is afterwards impregnated
during the precipitation. Other zeolites
contain exactly the fame fubftan-
ces, only in different proportions.
O f thofe which I have hitherto examined,
the Jemtland zeolite contains
the greateft quantity o f calcareous
earth, that is to fay, 1 6 parts in i co,
and that from Feroe the lead, namely,
8 in 100. The red zeolite from
Adelfors contains the greateil quantity
o f iiliceous earth, to wit, 80 in
100, and the Icelandic the leail, to wit,
48 in 100. The zeolite from Feroe
contains moil argillaceous earth, namely,
about 25 in 100, and that from
Adelfors the leail, or about 9 in 100.
I When
37i ]
When the original compoiition o f any
kind o f ilone is thus known, it is not
difficult to determine its qualities.
The zeolites at firil froth and fwell
in the fire, the caufe o f which has been
already explained.
They afterwards fufe more or lefs
perfectly. The fwapparara kind may
be reduced to a clear glafs, and the
Upland red zeolite can hardly be
brought to give any figns o f vitrification
on the furface.
It is well known that quarzj pure
argillaceous earth, and lime cannot fe-
parately be made to fufe, nor two and
two mixed together in many cafes; but
wdien all three are compounded, they
are more or lefs inclined to fufion. One
part o f pure argillaceous earth, with
one part o f lime, and two and a half to
three parts o f quarz, afford a mixture
which is eaiieil brought to fufe. I f the
compoiition o f the zeolites is compared
with this mixture, they are found to
be fufible in the fame meafure as the
proportion o f their conftituent parts
approaches more or lefs to the above-
mentioned compoiition.
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