ioo An ANALYSIS of 



union with which they had loft their ftrong attraction for 

 water. 



The conftituent parts of thefe extracts were next to be inve- 

 ftigated. I foon perceived that they contained a portion of al- 

 kaline fait not faturated with acid, which became evident when 

 a fmall quantity of them was wetted and applied to paper 

 ftained with the juice of violets, or the colouring matter of the 

 common purple radifh ; the colour in either cafe was changed 

 to a green, I further collected and fcraped thefe extracts out 

 of the glafTes, and placing each in a fmall filtre, I dropped di- 

 flilled water on them repeatedly, until the water came away 

 from them infipid. The waters which had been thus filtrated 

 through them were put into china cups, and the greater part 

 evaporated with a gentle heat, the reft was allowed to evapo- 

 rate fpontaneoufly in a dry room. Thus, a number of fmall 

 faiine cryftals were formed, which were partly regular cryftals 

 of common fait, and partly cryftals of an oblong and flatted 

 form, larger than thofe of the common fait. Thefe larger 

 cryftals were diltinguifhable, not only by their form, but by 

 fome of their properties. They became white, opaque and 

 mealy in dry air, and being taken out, and tafted and tried in 

 different ways, were found to contain fome of the fofhl alkali 

 in a cryftalized ftate. 



The undiffolved matter which had remained on the filtrating 

 paper, appeared by its properties to be totally or principally 

 made up of filiceous earth. It was white and exceedingly 

 fpungy and light. A fmall portion of it was triturated, and 

 made into a pafte with water ', which pafte being laid on a piece 

 of charcoal and dried, was heated intenfely with the blowpipe. 

 No part of it was melted ; it was only contracted in its dimen- 

 fions, and acquired a weak degree of cohefion. Another fmall 

 portion was triturated dry, with an equal weight of aerated and 

 exficcated fofTil alkali j and being put into a fmall platina fpoort, 

 againft the bottom of which the flame of the blowpipe was 



ftrongly 



