152 THE DIALYSATION PROCESS 



conclusion of the test some parts of this albumen 

 may fall into the dialysate and pollute it. During 

 the operation of cleansing the inside of the tubes, 

 care must be taken to prevent water from entering 

 the tubes. Before touching the tubes the hands 

 should be thoroughly cleansed. The use of forceps 

 is much recommended, and these must have wide, 

 parallel, smooth arms. 



The rinsed tubes are again put into Erlenmeyer 

 flasks which contain 20 c.c. of sterile distilled water. 

 The filling of the dialysation tubes must never be 

 done in the same flasks in which it is intended to 

 carry out the dialysation ; something out of the 

 pipette may too easily get into the flask. In order 

 to prevent contamination the surrounding fluid, as 

 well as the contents of the tubes, is covered with a 

 layer of toluol about \ cm. thick (fig. 7, p. 151). It 

 is best to cover the flasks with watch glasses, unless 

 one is prepared to use stoppered vessels. The 

 dialysation is carried on at the temperature of the 

 room, or, better still, in a closed space at a constant 

 temperature i.e., in an incubator. 



After about sixteen hours time is of no import- 

 ance in this test, since the tubes are in this case 

 merely tested for their permeability towards colloids 

 -the dialysation is interrupted. The Erlenmeyer 

 flasks, which should bear corresponding numbers, 

 are placed in a row. By means of a pipette, which is 



