222 SELECTED ARTICLES. 
other, they would be removed by the experiment of M. Vau- 
quelin, on the displacement of simple water mixed with sand 
by salt water poured on the surface of this latter. In practice, 
the advantages premised by theory are not always realized, be- 
cause the materials cannot be invariably in a proper state of di- 
vision; because they may be packed or pressed unequally, 
thus permitting the fluid to escape through some parts with 
too much rapidity; finally, because the different strata of fluid 
mix with each other. 
Lixiviation was not applied to pharmaceutic preparations, 
or rather this application was almost forgotten, when MM. 
Boullay pointed out the advantages of it. They gave it the 
name of displacement, because strata of the same fluid mu- 
tually displaced each other, or one fluid displaced another. 
It is true M. Payen had advised this process, and M. Robiquet 
had employed it in certain chemical investigations, but its real 
application to pharmaceutic preparations appears to be owing 
to MM. Boullay. Displacement is therefore lixiviation em- 
ployed on animal and vegetable substances, and affords results 
in most cases, more consonant to the theory, than processes in 
the arts, on account of the circumstances being more favourable; 
the powders employed are better prepared, and greater care is 
used in the process. 
MM. Boullay have generalized this method of displacement, 
but they have published but few facts with regard to it; M. 
Simonin applied it to the treatment of ratanhy and sarsaparil- 
la; W. Dublanc used it to prepare the extract of pomegranite 
root. The most important information on the subject is that 
published by M. Guillermond, jr. It is not that M. Guiller- 
mond applied the process to a great number of different sub- 
stances, but he was the first to make experiments on the ad- 
vantages it possessed over other methods of extraction, espe- 
cially over one long since proposed by Cadet Gassicourt, and 
which in some cases still merits the preference; this consists 
of moistening the powder with double its weight of water, 
and subjecting it to pressure after a few hours of maceration. 
M- Guillermond has also studied in a very satisfactory manner 
