LIXIVIATION OF VEGETABLE AND ANIMAL SUBSTANCES. 225 
diminishes the porosity of the substance, and consequently the 
rapidity with which the fluid passes through. The augmenta- 
tion of bulk, on the contrary, is a disadvantage, when it is too 
great, as happens with substances of an open texture, as well 
as with articles containing much mucus. I hence prefer em- 
ploying a method advised by M. Dausse for certain substances, 
but which is applicable to all. It consists in moistening the 
powder with half its weight of cold water, and letting it ma- 
cerate for some hours before introducing it into the apparatus. 
By this means, each article augments in bulk in proportion to 
its texture; the soluble portions are softened, and the powder 
is more speedily and completely exhausted. 
The quantity of w T ater indicated is sufficient to moisten 
most vegetable powders; it must be reduced to one-half with 
galls, but it is rarely necessary to augment it. Displacement 
is to be performed with cold water, except with certain sub- 
stances, as poppy flowers, senna, &c, the soluble portions of 
which are better acted upon by boiling water. As before 
mentioned, the powders are to be pressed or packed in the 
cylinders with a force which varies with almost every one of 
them; the following examples, however, may give some idea 
of the relative differences that exist, though it is by no means 
to be taken as an unvarying guide. 
The following are to be compressed forcibly: 
Arnica, Chamomile, 
Hops, Quassia, 
Pariera brava, and all other very ligneous substances. 
To be compressed tolerably firmly: 
Bistort, Kahinca, 
Dulcamara, Ipecacuanha, 
Cinchona, Ratanhy, 
Liquorice, Sarsaparilla, 
Valerian, and substances of a ligneous texture. 
To be moderately compressed: 
Wormwood, Belladonna, 
Aconite, Conium, 
Chicory, Rhus radicans, 
Stramonium, &c. 
vol. II. — no. in. 29 
