This is a very important substance in homoeopathic pharmacy, and great care must be taken to insure its purity. It has been selected for the purposes to which it is applied for two reasons - 1st, because it is devoid of all medicinal action; and 2nd, because its crystalline particles are very hard, and hence are of great use in grinding down the particles of drugs submitted to the process of trituration. It is never found pure in commerce, and even that which is professedly prepared for homoeopathic use is very seldom free from adulteration. Starch is very commonly found mixed with it, and this will seriously interfere with its triturating power. The homoeopathic chemist should examine every sample when purchased, before attempting to use it for triturations. The powder should answer to the following

Characters and Test. - Scentl ess, gritty to the touch, faintly sweet. Boiled with water and cooled, it gives no blue colour with an aqueous Solution of Iodine.

The ordinary commercial article may be refined for our purpose by solution in distilled water and careful re-crystallization, until it assumes the requisite purity and whiteness. It is then pulverized as finely as possible in a perfectly clean mortar, and sifted through a fine hair drum-sieve, which must not be used for other purposes.

The sugar should be kept in a dry, cool place, in well-closed glass jars.

Having thus given an account of the menstrua employed in the preparation of homoeopathic drugs, it is necessary in the next place to lay down a few general rules for the selection of the remedies themselves.