II 



BUTTER 



171 



the condenser and the distillation proceeded with. The flame 

 must be so regulated that the 110 c.c. of distillate pass over in 

 from 19-21 minutes, and the temperature of the condenser 

 must be so adjusted that the distillate is neither too warm nor 

 too cold, but enters 

 the flask at from 20- 

 23. Wiedemann 1 has 

 proposed the following 

 arrangement for easily 

 obtaining a constant 

 temperature : Rubber 

 tubing is put through 

 the inlet and outlet 

 tubes of the Liebig 

 condenser and pushed 

 along to within a few 

 centimetres of where 

 the side tubes are 

 fixed. Cold water en- 

 tering from below is 

 driven up the rubber 

 tubing into the upper 

 part of the condenser, 

 but sinks owing to its 

 greater density to the 

 lower part of the con- 

 denser, where it then 

 reaches the mouth of 

 the rubber tubing 

 going to the outlet, 

 and so flows away. By 



this means the temperature of the condenser water can be 

 kept almost constant at the desired temperature. 



As soon as the distillate reaches 110 c.c. the flame is removed, 

 and the receiving flask replaced by a 25 c.c. measuring cylinder. 

 The flask containing the distillate is placed, without being shaken, 

 for ten minutes in water of 15 C., and sunk until the 110 c.c. 

 mark is some 3 cm. below the water level. At the end of the first 

 five minutes the flask is moved to and fro but not so vigorously 



1 Molkerei-Zeitung, Hildesheim, 1904, p. 681. 



FIG. 65. Polenske's Distillation Apparatus. 



