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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, rre; filter paper wicks, w, and w' ; glass tube, t; 

 rubber connection, r; cork hanger, c; supply of water, s; base of stand, b. X 1. 



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 diaphragm and paper are then withdrawn and the paper trim- 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 



