fome chemical 'Experiments on Tabafheer. 373 
furface by means of fome of the allies of the charcoal fettling 
•upon it unobfefved, appeared by its undergoing the fame 
change when fixed to the end of a glafs tube, in the method 
of M. de Saussure *. 
With acids . 
§ V. (A) A piece of Tabafheer, weighing r.2 gr. was 
firft let fatiate itfelf with diftiiled water; its furface being 
then wiped dry, it was put into a matrafs with fome pure 
white marine acid, whofe fpecific gravity was 1.13. No effer- 
vefcence arofe on its immerfion into the acid ; nor did this 
menftruum, even by ebullition, feem to have any adion upon 
it, or itfelf receive any colour. The acid being evaporated 
left only fome dark coloured fpots on the 'glafs, Thefe 
fpots were diffolved by diftiiled water. No precipitation was 
produced in this water by vitriolic acid, or by a folution of 
cryftals of foda. The bit of Tabafheer wafhed with water, 
and made red hot, had not fuftained any lofs of weight. 
The pores of the mafs of Tabafheer were filled with water 
before it was put into the acid, to expel the common air con- 
tained in them, and which would have made it impoffible to 
afcertain with accuracy whether any effervefcence was pro-, 
duced on its firft contad with the menftruum. 
(B) Another portion of Tabafheer, weighing 10.2 gr. 
was boiled in fome of the fame marine acid. Not the leaf! 
precipitate was produced on faturating this acid with folution 
of mild foda. This Tabafheer alfo, after having been 
% Journal de Phyfique, Tom, XXVI. p. 409. 
boiled 
