26G Klaproth on the Chemical Anali/sis 



Prussiateof. potassa and tincture of galls gave characteristic 

 green and red precipitates in the muriatic solution of the above 

 carbonate. 



b. The alcaline washings of the carbonate did not become in 

 the smallest degree turbid when neutralized by sulphuric acid. 



This mineral therefore is to be regarded as pure oxide of 

 titanium. 



Analysis of the Topaz. 



This mineral is especially characterized by the changes which 

 it undergoes when subjected to a white heat ; it then com- 

 pletely loses its original appearance, becomes soft, dull-white, 

 and opaque, and loses considerably in weight. 



[Here follows an account of the causes to which this loss of 

 weight have been erroneously attributed, and to the experi- 

 ments of Margraaf, Bergman, Wiegleb, Vauquelin, and Lowitz ; 

 the author also alludes to the probable existence of fluoric acid 

 in the topaz, and then proceeds with his Analysis.] 



Analysis of the Saxon Topaz. Sp. gr. 3.545. 

 A. 



100 parts of coarsely -powdered topaz heated till the frag- 

 ments began to fuse, in a coated retort, connected with the mer- 

 curio-pneumatic apparatus, afforded no gaseous matter, and 

 lost little in weight. 



The same portion, heated to whiteness in a blast-furnace for 

 an hour, became white and pulverulent, and lost 22 per cent, in 

 weight. 



B. 



300 grains of powdered topaz, distilled to dryness with sul- 

 phuric acid, produced a corrosion in the neck of the retort, 

 resembling that of fluoric acid. 



C. 



200 grains of powdered topaz were projected into an ounce 

 of nitre, fused in a platinum crucible; the mixture after a time 

 concreted. The alcaline mass was then softened in water 



