264 Dr Turner on Lithion-Mica. 



curs in all the micas I have hitherto examined. The method 

 employed by Berzelius in his analysis of the topaz was 

 therefore resorted to ; but as it is one of some delicacy, I 

 shall describe the various parts of the process carefully. 



A 

 29.38 grains of the mica, in powder, were mixed with three 

 times their weight of carbonate of soda, and ignited during the 

 space of half an hour in a moderate red heat. The mass 

 had contracted greatly, and was of a dirty-yellow colour, 

 stained green in parts by manganese. It was treated by suc- 

 cessive portions of hot water, till all the soluble alkaline mat- 

 ter was completely removed. 



B 

 Carbonate of ammonia was now added to the alkaline solu- 

 tion, and it was then exposed to a temperature of about 100°F., 

 till the ammoniacal odour had completely ceased, by which 

 means the portion of alumina and silica, at first dissolved by 

 the soda, was deposited. The liquid, after filtration, was 

 exactly neutralized by muriatic acid, and the fluoric acid 

 precipitated by muriate of lime. The fluate of lime, after 

 being ignited, weighed 5.41 grains, equivalent (on the suppo- 

 sition that 100 fluate of lime contain 27.86 of fluoric acid) to 

 1.509 grains, or 5.138 per cent., of fluoric acid. 



C 

 The matter that was undissolved by water in A, together 

 with what separated from the alkaline solution in B, was dis- 

 solved by muriatic acid. The solution was evaporated to 

 dryness ; the soluble parts were taken up by water acidulated 

 with muriatic acid, and the silica collected on a filtre. After 

 ignition, it weighed 15.07 grains, which is 44.277 per cent. 



D 

 To the acid liquid, while cold and moderately diluted, a 

 solution of carbonate of soda was gradually added, till the 

 alumina and iron were precipitated. They were separated 

 from one another, after filtration, by pure potash. The alu- 

 mina, after exposure to a white heat, weighed 8.349 grains, 

 which is 24.532 per cent. The ignited peroxide of iron 

 amounted to 3.709 grains, equivalent to 3.329 grains, or 





