SOO VOLATILE MATERIALS IN SILICATES. 



of weight should be soluble in nitrate of ammonia, 

 with no other residue but the ashes of the filter. 2d. 

 By adding ammonia-phosphate of soda to the ammo- 

 niacal solution of magnesia, the bulky precipitate of 

 phosphate of ammonia and magnesia is formed. 3d. 

 The manganese is verified as above stated. 4th. The 

 chlorides of sodium and potassium are evaporated, 

 gently ignited, and when treated with a mixture of 

 alcohol and ether should not give any substance capa- 

 ble of coloring the flame red, which would indicate 

 the presence of lithia. 



The materials which are decomposed by acids are 

 treated directly in the same manner as those that are 

 rendered decomposable by lime ; but it is necessary to 

 do this in such a manner that the silica is always sepa- 

 rated in a gelatinous mass. If not, it is necessary to 

 ignite it with lime to bring it into this state. Thus 

 our condition is that the substance can be decomposed 

 by acid, producing gelatinous silica. The glass re- 

 sulting from the decomposition of the mineral by lime, 

 should have for its weight the sum of the weights of 

 the materials used, and the lime added. The difference 

 should be one milligramme, or two milligrammes at 

 most ; it is more frequently nothing. 



Examination of the volatile materials in silicates. 



It has been seen at the commencement of the analy- 

 sis of the silicates that it is necessary to heat the sub- 

 stance to a very high temperature to expel the volatile 

 materials. The water is freed at the temperature ob- 

 tained by the small lamp ; but when it is necessary to 

 use the large lamp, the presence of fluorides is indi- 

 cated. 



The better way to make the presence of water in a 

 mineral evident, is to place the material in a platinum 

 tube, and pass a current of dry gas through the tube 



