FREE BOOKS

Author's List




PREV.   NEXT  
|<   86   87   88   89   90   91   92   93   94   95   96   97   98   99   100   101   >>  
of London, undertook an analysis of tabasheer, the specimens being supplied from Brewster's collection (_Edinburgh Journal of Science_, vol. 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. While the ashes of the wood contained 0.0612 of the whole weight of the wood, the pith was found to contain 0.448 per cent., the inner wood much less, and the greatest proportion occurred in the external wood. On these determinations Guibourt founded a theory of the mode of formation of tabasheer based on the suggestion that at certain periods of its growth the bamboo needed less silica than at other times, and that when not needed, the silica was carried inward and deposited in the interior. In the year 1857, D.W. Host van Tonningen, of Buitenzorg, undertook an investigation of the tabasheer of Java, which is known to the natives of that island under the name of "singkara" (_Naturkundig Tijdschrift voor Nederlandsch Indie_, vol. xiii., 1857, p. 391). The specimens examined were obtained from the _Bambusa apus_, growing in the Residency of Bantam. It is described as resembling in appearance the Indian tabasheers. Its analysis gave the following result: Silica.
PREV.   NEXT  
|<   86   87   88   89   90   91   92   93   94   95   96   97   98   99   100   101   >>  



Top keywords:

tabasheer

 

silica

 

Guibourt

 
matter
 

obtained

 
Brewster
 

quantity

 
result
 

analysis

 

specimens


needed

 

undertook

 

Silica

 

Indian

 
varieties
 
Chalky
 
Transparent
 

Translucent

 

specific

 

bamboo


determinations
 

formation

 

periods

 
suggestion
 

composition

 

weight

 

greatest

 

founded

 
external
 
contained

proportion
 

occurred

 
theory
 

Bantam

 
Residency
 

island

 

natives

 

resembling

 

singkara

 

Naturkundig


examined

 

growing

 

Tijdschrift

 

Nederlandsch

 

carried

 

deposited

 

tabasheers

 
interior
 

Bambusa

 

appearance