102 
ON A NEW DISPLACEMENT APPARATUS. 
sions or decoctions to be used as such, or to be made into 
extracts or fluid extracts it may be applied with advantage. 
Where the menstruum is homogeneous as water, or alcohol, 
the process works very well, but when mixed liquids like 
diluted alcohol are to be vaporized, the greater volatility 
of one than the other is a strong objection. 
A process somewhat like this has been patented in Eu- 
rope for extracting the coloring matter from dyewoods, 
which consists in saturating the wood in fine chips or shav- 
ings with steam, and when they are swelled with condensed 
vapour, boiling water is poured on and boiled. The ap- 
paratus under consideration will no doubt answer for the 
same use, with the additional advantage of givinga concen- 
trated infusion or rather decoction. N 
With reference to the working of the apparatus, apart 
from its principle of action, it may be remarked, that as the 
condensing surface is applied merely to the external surface 
of the ingredients in contact with the sides of the displacer, 
it follows that that portion of the substance receives the 
action of the largest portion of the condensed vapour. It 
may easily be conceived that the central portion of the in- 
gredients for some depth may become so hot as not to con- 
dense the vapour, and consequently to receive but little 
action from the condensed fluid, which is in accordance 
with experiment. In the case of black hellebore, above 
stated, while that portion of the root near the sides of the 
displacer was tasteless, the central portion, amounting to 
about one-fourth or one-fifth, of the whole, was strongly 
bitter, notwithstanding a larger amount of menstruum 
had been employed than was directed for that quantity 
of root. The same was found to occur in the case of the 
ginger, although to a less extent. This difficulty might be 
remedied by having the substance placed between two 
concentric cylinders with cool water applied to each sur- 
face, which would increase the surface of condensation. 
There is a decided advantage obtained by permitting the 
vapour to pass over and condense among the particles of 
