Siliceous Earth, 9 



3 d - It combines with no acid hitherto known, 

 except the fparry, which either in a liquid or 

 Aerial ftate, but particularly in the latter, is ca- 

 pable of holding much of it in folution, 

 which it depofits either on cooling or coming 

 in contaft with water, or fubftances with 

 which it has a greater affinity. But cauftic fixed 

 alkalis may even in the liquid way take up 

 from T V to -^ of their weight of this Earth 

 according as it is more or lefs fubtilly divi- 

 jded, and hence it is not improbable that even 

 lime-water has fome adtion on it. 



4 th - It is infufible^r/? in the ftrongeft heat, 

 neither does argillaceous or magnefian Earths 

 promote its fufion, the effeft of calcareous 

 Earth is fomew r hat more doubtful, for Mr* 

 Achard * and Mr. Schcffer^ aflert that thefe 

 Earths do not melt together, but Mr. Darcet^ 

 and alfo Mr. Bergman^ and Mr. Swab, \\ fay 

 that two parts lime melt one of quartz ; at leaft 

 there is no doubt but this may be effected in 

 veffels of clay, for an admixture of this will 

 make the other two Earths immediately 

 yield. Fixed alkalis, particularly the mineral, 

 readily melt double their weight of this Earth 

 with effervefcence, borax affects it more dif- 

 ficultly, and with fcarce any effervefcence, 

 and microcofmip fait has hardly any aftion 



* Mem. Berlin, 1780, p. 32. f Foreles. 174, b< 

 ; 22 Koz. p. 27. ScheiT. Foreles, 175, b, 2 Anmerk. 

 |) 2 Memoires d'LJpfal, p. 443, 



on 



