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poured off, and the undissolved mass washedand shaken in distilled water; the whole thrownon a filtre, and sweetened as long as the waterthat passes through has any taste. The con-tents of this water should be precipitated by asolution of mild mineral alkali: this precipitatealso being washed and dried in a heat belowredness, should then be weighed. Thus wehave another method of finding the weight ofthe calcareous matter.

11 0 ' The undissolved mass is next to be driedin the heat already mentioned, and the differ-ence between its weight and the weight of thewhole earthy mass before solution should benoted, as it furnishes a third method of dis-covering the weight of the calcareous matter ofwhich it is now deprived. Supposing this toamount to 150 grains, the weight of the undis-solved residuum should in the above case be383—150=235 grains.

12°' Reduce the dried mass into the finestpowder, throw it into a Florence flask or glassretort, and pour on it three times its weightof pure oil of vitriol, digest in a strong sandheat, and at last raise the heat so as to make