40 | CHEMISTRY. 
The substance from which the extract is to be made, must be introduced 
into the cylinder, A, on a sieve bottom, d, covered by a cloth, and pressed 
upon by a second superimposed perforated bottom, e, lightly pressed against 
the substance during the operation by screws passing through the cover : 
this is attached by clamps. _The liquid by means of which the extract is te 
be made is poured upon the stamper, GE, by means of a measure (fig. 50), 
graduated on the inside. On raising the piston, E, this passes through the 
valve, e, into the lower space of the cylinder, and on depressing the piston, 
through the valve, a, into the canal, & presses against the sieve bottom, ), 
and the substance between d and e, and collects above e, in the space B, 
from which it can be readily removed. 
Fig. 68 is also an extract press, in which a pressure is exerted by means 
of the piston, DE, on the liquid in the space G, which covers the substance 
whose extract is to be obtained. B is a filtering apparatus. By opening 
the stopper, b, the liquid is introduced. It is removed by turning the 
cock c. \ 
Pl. 30, fig. 68. An apparatus for producing small quantities of illumi- 
nating gas from various substances. ‘The substances to be exposed to a dry 
distillation are placed in d. The gas passes through the connecting tube, C, 
into the receiver, 6, which may be removed at pleasure, or from which the 
gas may be let off by means of a cock, e, and the tube a, or else may be 
burned by means of a burner set on a. 
Pl. 30, fig.64. Argand’s Oil Lamp, for drying precipitates or filters. 
A movable arm slides on the stand A, and can be fixed by means of a screw. 
This arm carries the furnace, C. Bis an Argand lamp. A boiler is placed 
in C, having a lateral escape pipe for letting off the steam. D is a glass 
vessel with a rim, which rests on the edge of the boiler and closes it. In 
this vessel the filter to be dried is laid, and fixed by means of the piece E. 
When the water in the boiler has been made to boil by the lamp, the 
inside of the glass vessel becomes heated, and the filter dries rapidly. 
IX. Tue Cuemicat Laporatory at GIESSEN. 
The first requisite to a satisfactory pursuit of chemistry, is, in every 
‘instance, as well regulated and complete a laboratory as possible. No 
science is so dependent on experiment as chemistry, every fact requiring 
ocular demonstration. For this reason every facility rendered to chemical 
operations is a clear gain. Private laboratories are no guide to the general 
investigator, each individual arranging his own premises according to his 
particular line of study. Universities, however, and technical establish- 
ments, should not be without complete laboratories, in which all imaginable 
operations may be carried on. We have therefore concluded to present to 
our readers an idea of a chemical laboratory, the first one established in 
Europe on a large scale, and one in which, under the direction of its distin- 
guished founder, Liebig, a host of young chemists have been trained for 
years past, and in which some of the most important contributions to 
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