THE DIALYSATIOX PROCESS 153 



closed at its upper extremity by the finger and rapidly 

 passed through the layer of toluol, 10 c.c. of the 

 dialysate are taken out, and placed in a test-tube 

 bearing the same number as the corresponding 

 Erlenmever flask. This is the best way to avoid 



/ 



mistakes. Of course, for each dialysate a separate 

 and absolutely clean pipette must be used. We do 

 not recommend transferring the dialysates to the 

 test-tubes by means of the same pipette, rapidly 

 cleansed each time after use, because by this means 

 some impurity or other may easily be introduced into 

 the dialysate. Some saliva may very easily enter 

 that part of the pipette which, during the so-called 

 cleansing, remains untouched by the water, alcohol 

 and ether. On the contrary, new saliva is drawn in 

 at each operation if the suction is made by the mouth. 

 Xo\v, when the dialysate is taken up, it is almost 

 certain to be drawn above the level marked upon the 

 pipette, and may then become mixed with the saliva. 

 If test-tubes, graduated to 10 c.c., are to hand, then 

 these tubes may be employed in the following man- 

 ner : After removing the dialvsing tubes, the toluol 

 is drawn off and the dialysate is poured directly into 

 the test-tube. It is of no great importance, in the 

 biuret reaction, to consider quantities to the minutest 

 exactness, nor does a little toluol do any harm. 



Now, to each test-tube is added about 2*5 c.c. of a 

 33 per cent, caustic soda solution. The whole is shaken 



