MOHR AND REDWOOD'S PRACTICAL PHARMACY. 215 
In the last number of this Journal, a series of pretty 
copious selections are inserted, calculated to show its gene- 
ral scope and character ; and with these brief preliminary 
remarks, we will proceed to give further extracts from it, 
confining ourselves chiefly to the chapters on extempora- 
neous pharmacy, conscious that in this way we can give 
a better idea of the book, than by any observations of our 
own respecting it: 
" The presence of soluble salts in an emulsion generally 
tends to cause a separation of the oil. Much spirit will 
produce a similar effect, especially in emulsions made with 
mucilage ; and acids, in those made with alkali. Alkaline 
salts, however, in small quantity, are beneficial. Thus, a 
little borax will often be found greatly to improve an emul- 
sion. 
e * There are some substances which cannot be formed 
into good emulsions with an alkali or with mucilage. Sper- 
maceti and other solid fats belong to this class, and so also 
does oil of turpentine. In such cases yolk of egg is the best 
agent for effecting the admixture, the ingredients being 
rubbed together in a mortar ; and, should any difficulty be 
expected, the oily or fatty body should be added gradually 
to the yolk of egg, and the mixture diluted with a little 
water, from time to time, as it thickens. 
" Volatile oils are more readily emulsionized by previous 
admixture with a little fixed oil — especially those of the 
turpentine class, as oil of copaiba, cubebs, cajuput, etc. The 
yolk of egg owes its advantages over the white, for this 
purpose, to the fact that it is itself a natural mixture of fixed 
oil and albumen. A good spermaceti mixture may be 
made by triturating that substance with half its weight of 
olive oil, then adding the proper quantity of gum arabic, 
and after mixing them, adding the water gradually, in the 
usual manner of making an emulsion. Camphor is fre- 
quently prescribed in mixtures suspended with mucilage. It 
is usually pulverized by the addition of alcohol, triturated 
