Chemical Examination of American Minerals. 15 



nese, still contains lime and a fixed alkali. It is to be heated, 

 and oxalate of ammonia added to it as long as any precipi- 

 tate falls. Let this precipitate, which is oxalate of lime, col- 

 lect at the bottom of the vessel ; decant off the pure liquid, 

 and throw the oxalate of lime upon a double filter, wash it 

 completely, then dry it, and determine the weight on the filter. 

 As much of it as is convenient, is to be put into a balanced 

 platinum crucible, and heated over the spirit-lamp till the 

 oxalic acid is destroyed, and the charcoal at first evolved 

 burnt away. Then mix the residual matter with a little car- 

 bonate of ammonia, and expose the mixture to the heat of 

 the lamp, till the ammoniacal fumes are dissipated. It is 

 now carbonate of lime containing Vths of its weight of lime. 

 It is easy from the weight of carbonate thus obtained, to de- 

 duce that of the whole lime contained in the mineral. 



/. The liquid thus freed from lime, still retains the fixed 

 alkali. Evaporate it to dryness, and heat the residual salt in 

 a platinum crucible (taking care not to fuse it) till all ammo- 

 niacal fumes are dissipated ; what remains is an alkaline 

 chloride. To determine its nature dissolve it in a little water, 

 and add to the solution some muriate of platinum. If the 

 alkali be potash, a yellow precipitate will fall ; but none will 

 appear if the alkali be soda ; ^^, or Ifths of the weight, indi- 

 cates the quantity of potash, if the salt was a chloride of po- 

 tassium ; j^, or T^ths of the weight, is the quantity of soda 

 contained in chloride of sodium. Chloride of potassium, and 

 chloride of sodium, are permanent in the air ; but chloride of 

 lithium deliquesces. 



2. When the mineral requires heating with an alkaline 

 carbonate, an additional step in the analysis is requisite. 

 Either carbonate of potash, or carbonate of soda, may be used 

 at pleasure. I always make use of carbonate of soda, merely 

 because I can easily procure it sufiiciently ptire for the pur- 

 pose ; whereas the carbonate of potash in this country would 



