106 PHILOSOPHICAL TRANSACTIONS. [aNNO IJQl. 



then added to the acid, (b) This tabasheer was put back into the alkaline solu- 

 tion, which seemed not impaired by the foregoing process, and again boiled for 

 a considerable time. The liquor was then poured from it while hot, and the 

 tabasheer edulcorated with some cold distilled water, which was afterwards mixed 

 with this hot solution, in which it instantly caused a precipitation. On heating 

 the mixture it became clear again; but as it cooled it changed wholly into a thin 

 jelly; but in the course of a few days it separated into 2 portions, the jelly 

 settling in a denser state to the bottom of the vessel, leaving a limpid liquor 

 over it. 



(c) The tabasheer remaining (b) was boiled in pure marine acid; the acid 

 was then poured off, and the tabasheer edulcorated with some distilled water, 

 which was afterwards mixed with the acid, (d) The remaining tabasheer col- 

 lected, washed, and dried, weighed 24 gr. and seemed not to be altered, (e) 

 The acid liquors (a and c) were mixed together, and saturated with soda, but 

 afforded no precipitate, (f) The alkaline mixture (b) was poured on a filter, 

 the clear liquor came through, leaving the jelly on the paper. Some of this 

 clear liquor, exposed to the air in a saucer, at the end of some days deposited a 

 small quantity of a gelatinous matter ; after some days more, the whole fluid 

 part exhaled, and the saucer became covered with regular crystals of soda, 

 which afforded no precipitate during their solution in vitriolic acid. What had 

 appeared like a jelly while moist, assumed on drying the form of a white 

 powder. This powder was insoluble in vitriolic acid, and seemed still to be 

 tabasheer. Some of this clear liquor, mixed with marine acid, effervesced ; did 

 not afford any precipitate ; but on standing some days the mixture became 

 slightly gelatinous, (g) Some of the thick jelly remaining on the filter, being 

 boiled in water and in marine acid, appeared insoluble in both, and seemed to 

 agree entirely with the above powder (p). 



With dry alkalis. — § 12. (a) Tabasheer melted on the charcoal at the blow- 

 pipe with soda, with considerable effervescence. When the proportion of 

 alkali was large, the tabasheer quickly dissolved, and the whole spread on the 

 coal, soaked into it, and vanished; but, by adding the alkali to the bit of taba- 

 sheer in exceedingly small quantities at a time, this substance was converted 

 into a pearl of clear colourless glass. 



(b) 3 gr. of tabasheer, reduced to fine powder, were melted into a platina 

 crucible with 100 gr. of crystals of soda. The mass obtained was white and 

 opaque, and weighed 40.2 gr. Put into an ounce of distilled water, it wholly 

 dissolved. An excess of marine acid let fall into this solution produced an effer- 

 vescence, and changed it into a jelly. This mixture was stirred about, and then 

 thrown into a filter. The jelly left on the paper did not dissolve in marine acid 

 by ebullition; collected, washed with distilled water, and dried, it weighed 



