DETERMINATION OF ALKALIES IN MINERALS. 205 



described, and without any particular care in levigating them. 

 One gramme of the zircon, for instance, after being crushed 

 in the diamond mortar, was rubbed up for fifteen minutes in 

 a large agate mortar, and used. Its complete decomposition 

 was not only shown by its solution in hydrochloric acid, but 

 by the amount of zirconia obtained, which was 64.8 per cent., 

 with little iron. This concludes the first point to be consid- 

 ered in this article — namely, the means necessary to render 

 the silicates soluble. The next point is the separation of the 

 alkalies. 



II. Separation of the other Ingredients from the Alkalies. 



19. The platinum crucible, with its fused contents, is laid 

 on its side in a capsule of platinum or porcelain. The latter 

 can be used with perfect safety to the accuracy of the result. 

 A quantity of dilute hydrochloric acid is poured into the cap- 

 sule, one part of acid to two of water. The whole is heated 

 over a lamp, when the contents of the crucible are rapidly 

 dissolved out; the crucible is taken out and washed over the 

 capsule; the contents of the capsule are then evaporated to 

 dryness over a sand-bath; and, if thought necessary, it may be 

 completed over the lamp without danger of the spitting which 

 occurs in the soda fusion. This evaporation to dryness is not 

 absolutely necessary; but the advantage of it is that any great 

 excess of hydrochloric acid is got rid of, and the precipitate in 

 the next operation is less bulky than it otherwise would be. 



20. To the dry mass a little hydrochloric acid is added, and 

 then three or four ounces of water, or more, as the occasion 

 may require It is then boiled for a short time in the same 

 capsule, allowed to cool down a little, and then a concentrated 

 solution of carbonate of ammonia is slowly added until there 

 is an excess of the same. The solution becomes at first quite 

 thick with the precipitate, but in a short time (especially with 

 a little warming over the lamp) the precipitate accumulates in 

 a more or less granular state, and afterward occupies less space 

 in the filter than the alumina it might contain (in a feldspar, 

 for instance) were this latter precipitated separately by am- 

 monia; and this circumstance is of much importance in dimin- 

 ishing the length of the operations and the amount of water 

 accumulated by filtering it from several precipitates. 



