252 



The Philippine Journal of Science 



1918 



W 



means of regulating the maximum pressure of the water under 

 the filter floor. The assembled apparatus in use is represented 

 by fig. 3. 



In use the bend of the U tube is first filled with distilled water 

 to a level somewhat above the filter floor. Then, with the inlet 

 mouth and side tube closed, the tube is inverted with the filter 

 side lowermost, and shaken if necessary, to release all air bub- 

 bles from below the filter. It is returned to the upright posi- 

 tion and hung on a suitable sup- 

 port. Next, the open side is 

 filled with water up to the level 

 of the outlet, and the liquid con- 

 taining the specimens is quickly 

 poured into the other side, the 

 object being to prevent any fix- 

 ing fluid from passing through 

 the filter. In practice it is pref- 

 erable to decant superfluous fix- 

 ing fluid and dilute before pour- 

 ing into the washing apparatus. 

 After the specimens have been 

 allowed to settle, a narrow wick 

 of several layers of filter paper, 

 pointed at the outer end, is in- 

 serted in the outlet tube to in- 

 sure a steady outflow. The bent 

 tube on the side tube of the inlet 

 arm is provided with a similar 

 wick and adjusted to provide 

 for the maximum limit of pres- 

 sure. Washing water is allowed 

 to drop into the inlet mouth of 

 the U tube. 



A form of this apparatus having a larger capacity is made 

 by using an Erlenmeyer flask from which the bottom has been 

 cut with a diamond, the edges smoothed by heating over a flame, 

 and a spout, like that of a beaker, shaped in the larger end 

 as shown in fig. 4. The flasks used have a nearly cylindrical 

 neck about 4 cm long and 33 mm inside diameter, and it is 

 preferable that this inside diameter be smallest near the union 

 of the neck with the conical body of the flask. A ring dia- 

 phragm to fit tightly in the neck is cut from a cork or rubber 

 stopper. The aperture in the diaphragm should be large enough 

 to permit the exit of bubbles which may form between the dia- 



c 



Fig. 4. Larger washing apparatus made 

 from a flask. Diaphragm of cork or rubber, 

 d; filter paper, /; material, m; plug, p; 

 supporting rod, n; rubber stopper with two 

 holes, s; glass tubes, t and ('; rubber con- 

 nection, e; base, 6; filter paper wicks, w 

 and w' ; supply of water, x; wick in front 

 view of lip, w." X i. 



