METHODS OF OBTAINING POTASH.

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muriate of potash, with the portions of earth and even of car-bonic acid, which it obstinately retains, or which it may haveacquired from the air during the evaporation, remain at the bot-tom of the solution. Afterwards decant the pure liquor, and dis-til it in a retort till it becomes colourless. It must then be eva-porated in a silver bason! On cooling, it crystallizes in whitelaminae, which are sometimes three-tenths of an inch in length:or,-instead of suffering it to crystallize it may be evaporated todryness.

2. I.owitz has given another method.* According to thischemist the whole of the operation for obtaining potash of thegreatest purity, and without the least colour, consists in this: _Alixivium of potash, freed from carbonic acid in the usual manner,is evaporated to a thick pellicle. After the cooling, the foreignsalt which has crystallized is to be separated, and the evaporationof the lixivium continued in an iron pot. During this secondevaporation die pellicle of foreign salts, particularly of carbonateof potash, which continues to be formed, must be carefully takenoff with an iron skimmer. When no more pellicle is formed,and the matter ceases to boil up, it is removed from the fire andsuffered to cool, continually stirred with an iron spatula. It isthen to be dissolved in double the quantity of cold water, and thesolution filtered, and evaporated in. a glass retort, till it begins todeposit regular crystals. If the mass should consolidate ever solittle by cooling, a small quantity of water is to be added, andit must be heated again to render it fluid. After the formationof a sufficient quantity of regular crystals, the fluid, "which isvery brown, is to be decanted, and the salt, after being sufferedto drain, must be re-dissolved in the same quantity of water.The decanted fluid must be kept in a well-closed bottle, andsuffered to become clear by subsiding during several days. Itmust then be decanted for a second evaporation and crystalliza-tion. The process must be repeated as long as the crystals af-

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* Nicholson’s Journal, vol. i. p. 1 4.