XIII, C, 4 
Shaw: Microtechnical Methods 
251 
rubber tube with one of the side tubes, as shown in fig. 3. A 
perforated cork fitted over the same side tube serves as means 
of hanging the apparatus on a rack. Water is supplied 
from an aspirator bottle on a shelf and controlled by a screw 
compressor clamp on a rubber supply tube having a glass nozzle. 
The U tube has an inside diameter of about 18 mm and a cap- 
acity below the side tubes of about 58 cc, and in one arm be- 
tween the side tube and the filter floor holds about 15 cc. The 
diaphragm is a piece of cork or rubber stopper about 7 to 10 
mm high with the smaller end slightly smaller and the larger 
end slightly larger than the bore of the U tube, perforated with 
Fig. 3. Smaller washing apparatus made from a calcium chlorid tube. Diaphragm of 
cork or rubber, d; filter paper, /; material, m; filter paper wicks, w, and w' ; glass tube, t; 
rubber connection, r; cork hanger, c; supply of water, s; base of stand, b. X &. 
a hole about one-third the diameter of the stopper. A piece 
of dry filter paper is placed over one mouth of the U tube and 
pressed into the tube with the larger side of the diaphragm, 
the margin of the paper being crimped and bunched. The 
diaphragm and paper are then withdrawn and the paper trim- 
med to leave a suitable margin, after which the diaphragm with 
its paper cover is inserted into the mouth of the tube, smaller 
side first, and pressed down almost to the bend of the U tube 
with the blunt end of a cork borer of larger diameter than 
the perforation of the diaphragm. The bent tube has its longer 
arm about equal in length to the distance from the mouth of 
the U tube to the side tube, is connected with the side tube of 
the open arm of the U tube, the inlet arm, and serves as a 
