ON THE EXTRACT OF HEMLOCK. 
171 
3rd. Whether proof spirit, or rectified spirit, was the best men- 
struum for hemlock leaves. 
The evaporating processes, whose comparative merits were test- 
ed, were, 1st, Exposure in shallow vessels to the open air in warm 
dry weather. 
2nd. Exposure in shallow vessels to the influence of a continu- 
ous current of warm dry air. (In this instance an apparatus was 
employed precisely similar to that recommended in Mohr and Red- 
wood's Practical Pharmacy t p. 78, fig. 72.) 
3rd. Exposure to the heat of an ordinary water-bath. 
The result obtained by the first process is very satisfactory, so 
far as regards the quality and appearance of the extract obtained ; 
but there is a great obstacle to the adoption of this process, especi- 
ally on a large scale, viz: the uncertainty of the weather. It ap- 
pears probable that no more efficient and generally applicable 
means of effecting the inspissation of hemlock juice, and other 
analogous fluids, will be met with, than is afforded by the appli- 
cation of the principle of the hot-air closet before mentioned. 
In the use of such an apparatus we have the following advan~ 
tages : — 
The evaporating liquid requires no stirring or other attention 
from the commencement until the conclusion of the process. 
The temperature of the closet is perfectly at command, within a 
certain range; the evaporating liquid maintaining a temperature 
about 40° F. below the temperature of the air passing over it. 
For instance, we can easily obtain a current of air at 140° F. in 
the upper part of the apparatus, while the temperature of the li- 
quid placed there does not exceed 100° F. The rate of evapora- 
tion is quicker than might have been expected, though perhaps 
not so expeditious as many would deem desirable; still it was 
found that the evaporation might be greatly accelerated if means 
were provided for forcing the current of heated air more quickly 
over the surface of the liquid by the use of a blowing apparatus, 
similar in construction to those employed at iron-foundries and 
smelting houses. 
Evaporation by means of a water-bath is too well known to need 
any remark. 
It was thought likely that the chlorophylle and albumen contain- 
ed in the juice of hemlock might be removed with advantage, in 
