viii., 1828, p. 335). His
determinations of the specific gravities of different varieties were as
follows:
Chalky tabasheer. 2.189
Translucent tabasheer. 2.167
Transparent tabasheer. 2.160
All the varieties lose air and hygroscopic water at 100 deg. C., and a larger
quantity of water and organic matter (indicated by faint smoke and an
empyreumatic odor) at a red heat. The results obtained were as follows:
Loss at 100 deg. C. Loss at red heat.
Chalky tabasheer. 0.838 per cent. 1.277 per cent.
Translucent tabasheer. 1.620 " " 3.840 " "
Transparent tabasheer. 2.411 " " 4.518 " "
Dr. Turner found the ignited Indian tabasheer to consist almost entirely
of pure silica with a minute quantity of lime and vegetable matter. He
failed to find any trace of alkalies in it.
In 1855, Guibourt (_Journ. de Pharm_. [3], xxvii., 81, 161, 252; _Phil.
Mag_, [4], x., 229) analyzed a specimen of tabasheer having a specific
gravity of 2.148. It gave the following result:
Silica. = 96.94
Potash and lime. = 0.13
Water. = 2.93
Organic matter. = trace
Guibourt criticised some of the conclusions arrived at by Brewster, and
sought to explain the source of the silica by studying the composition of
different parts of the bamboo.
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