14 Chemical Examination of American Minerals. 



c. Collect the precipitate on a filter as before, wash it, dry 

 it, and expose it to a red heat, and then determine its weight. 

 Let it be a. 



Put it into a flask, and digest it in muriatic acid till a solu- 

 tion is obtained. A few white flocks of silica commonly re- 

 main. They are to be collected, edulcorated, ignited, and 

 weighed. This weight is to be added to that of the silica 

 already found, and deducted from the weight of a, which in- 

 dicates the alumina and oxide of iron in the mineral. To the 

 muriatic solution previously made nearly neutral by evapo- 

 ration, add a considerable excess of potash-ley, which need 

 not be very concentrated. • Heat this mixture in a flask, boil 

 it for some time, and the alumina will dissolve ; but the per- 

 oxide of iron will remain behind in the state of red flocks. 

 Collect the iron on a filter, wash it, dry it, and expose it to a 

 red heat, then weigh it ; let its weight be b. It is obvious 

 that the weight of the alumina is a — b. 



d. Sometimes manganese is also present in the liquid as 

 well as iron. In such cases, the precipitated peroxide of iron 

 (if we proceed in the way above directed) will contain the 

 manganese. The presence of manganese is easily detected 

 by a solution of chloride of lime. A drop of it let fall into a 

 liquid containing manganese, will immediately produce a red 

 precipitate in flocks. To separate the manganese from the 

 iron, the easiest way is to dissolve the mixture in muriatic 

 acid, and to pour into the solution, rendered as neutral as 

 possible by concentration, a solution of chloride of lime ; the 

 manganese falls in the state of a red powder. After edulco- 

 ration and ignition, 6 of this matter is equivalent to 4*5 pro- 

 toxide, or to 5 deutoxide of manganese. This amount being 

 subtracted from the original weight of the mixture of iron and 

 manganese, will leave the weight of the peroxide of iron con- 

 tained in the mineral under analysis. 



e. The liquid thus freed from alumina, iron, and manga- 



