TOL. LXXXI.3 PHILOSOPHICAL TKANSACTIONS. 107 



4.5 gr, and seemed to be the tabasheer unaltered. The liquor which had come 

 through, being saturated with mineral alkali, yielded only a very small quantity 

 of a red precipitate, which was the colouring matter of the pink blotting paper 

 through which it had been passed. 



(c) 10 gr. of tabasheer, reduced to powder, were mixed with an equal weight 

 of soda, deprived of its water of crystallization by heat. This mixture was put 

 into a platina crucible, and exposed to a strong fire for I 5"^. It was then found 

 converted into a transparent glass of a slight yellow colour. This glass was 

 broken into pieces, and boiled in marine acid. No effervescence appeared; but 

 the glass was dissolved into a jelly. This jelly, collected on a filter, well 

 washed, and dried, weighed 7-7 gr. The acid liquor which came through, on 

 saturation with soda, afforded not the least precipitate; but, after standing a 

 day or two, it changed into a thin jelly. This collected on a filter was washed 

 with distilled water, and then boiled in marine acid, but did not dissolve. Being 

 again edulcorated, and made red-hot, it weighed 1 .6 gr. The filtered liquor (b) 

 would in all probability have changed similarly to a jelly, had it been kept. 

 These precipitates were analogous to those ^ 9. (i). 



(c) An equal weight of vegetable alkali and tabasheer were melted together 

 in the platina crucible. The glass produced was transparent; but it had a fiery 

 taste, and soon attracted the moisture of the air, and dissolved into a thick 

 hquor. But two parts of vegetable alkali, with 3 of tabasheer, yielded a trans- 

 parent glass, which was permanent. 



Treated ivith other fluxes. — § 13. (a) A fragment of tabasheer put into glass 

 of borax, and urged at the blow-pipe, contracted very considerably in size, the 

 same as when heated per se; after which it continued turning about in the flux, 

 dissolving with great difficulty and very slowly. When the solution was 

 effected, the saline pearl remained perfectly clear and colourless, (b) With 

 phosphoric ammoniac (made by saturating the acid obtained by the slow com- 

 bustion of phosphorus with caustic volatile alkali) the tabasheer very readily 

 melted on the charcoal at the blow-pipe, with effervescence, into a white frothy 

 bead, (c) Fused, by the same means, on a plate of platina, with the vitriols of 

 tartar and soda, it appeared entirely to resist their action; the little particles 

 employed continuing to revolve in the fluid globules without sustaining any 

 sensible diminution of size, and the saline beads on cooling assumed their usual 

 opacity, (d) A bit of tabasheer was laid on a plate of silver, and a little litharge 

 was put over it, and then melted with the blow-pipe. It immediately acted on 

 the tabasheer, and covered it with a white glassy glazing. By the addition of 

 more litharge the mass was brought to a round bead, though with considerable 

 difficulty. This bead bore melting on the charcoal, without ally reduction of 

 the lead, but could not be obtained transparent. 



p 2 



