Chemical Examination of American Minerals. 17 



well known to analytical chemists. If it be heated to red- 

 ness, and then moistened with water, it becomes very hot. 

 This may be repeated as often as you please : pure alumina 

 has no such property. 



Let us suppose a mineral to be composed of silica, alumina, 

 lime, magnesia, and oxide of iron ; that it has been heated 

 with carbonate of soda, dissolved in muriatic acid, the acid 

 solution evaporated to dryness, and the residue digested in 

 water acidulated with muriatic acid, by which means every 

 thing is dissolved except the silica. The liquid containing 

 the lime, magnesia, alumina, and oxide of iron, dissolved in 

 an excess of muriatic acid, is put into a cylindrical glass jar, 

 furnished with a square of window glass large enough to 

 cover its mouth. Into this is poured (by small portions at a 

 time) a solution of bicarbonate of potash, or bicarbonate of 

 ammonia. After every addition a violent effervescence takes 

 place ; the glass plate must be put over the mouth of the 

 vessel, to prevent the loss which might be occasioned by the 

 little drops of liquid thrown out of the glass during efferves- 

 cence. This addition is to be continued till the liquid is su- 

 persaturated with the bicarbonate. The alumina and oxide 

 of iron are precipitated ; but the lime and magnesia remain 

 in solution, in the state of compound salts or bicarbonates. 

 The precipitated alumina and oxide of iron, are to be treated 

 and analyzed in the way already described. 



Let the liquid containing the lime and magnesia be satura- 

 ted with muriatic acid ; add a little caustic ammonia, and 

 then precipitate the lime by oxalate of ammonia. Treat the 

 oxalate of lime as before directed, in order to obtain the lime 

 in a separate state. 



The liquid thus freed from lime is to be made boiling hot, 



and while in that state, mixed with an excess of carbonate of 



soda. Boil it for two hours on the sand, and then separate 



the precipitated carbonate of magnesia by the filter. Evapo- 



VoL. III. 3 



