The preparation of this powerful medicine requires the greatest care. A mixture containing a few particles of phosphorus the size of a pin's head may easily occasion fatal gastritis. It is, therefore, most important that when it is ordered in a mixture it should be perfectly divided. Some pharmacists have recommended the solution of phosphorus in hot mucilage. It is liable, however, in cooling to form small particles like wax, which makes this method highly dangerous. It should be dissolved in 100 times its weight of almond or poppy oil in a test-tube by frequent dipping into hot water, and the oil solution emulsified in the proper way.

[The best plan to follow in such a case as this is to emulsify the proper quantity of the official ol. phosphorat. in the same manner as almond oil is emulsified with acacia. Fortunately, emulsions of this kind are seldom ordered in this country.-Ed.]

Wax, Spermaceti, and Cocoa-butter are emulsified like the fixed oils. The wax is melted and poured into a hot mortar, the pestle also being heated. To 10 grammes of wax an equal weight of gum is added, and 15 grammes of hot water is added gradually. After well mixing the mortar is partly cooled, and 85 grammes of cold water is stirred in gradually. Yellow wax should always be used for an emulsion. It gives a perfectly white emulsion. White wax cannot always be well emulsified, and the small proportion of tallow which it not infrequently contains is likely to impart to it a rancid taste.

[The rule may be safely laid down that fixed oils require the mortar and pestle, while volatile oils are better, as well as more quickly, emulsified by agitation.-Ed.]