POLENSKE METHOD. 



321 



the condenser is washed out with 18 c.c. of water, this 



being collected in the cylinder, poured into the flask, and 



used to wash the filter ; the last 10 c.c. of filtrate should be neut- 



N 

 ralised by one drop of — alkali solution. The funnel is removed 



to the flask in which the distillate was collected, and three suc- 

 cessive portions of neutral 

 '10 per cent. alcohol 

 (methylated spirit will 

 serve) are poured through 

 the condenser, cylinder, 

 and filter, and the com- 

 bined alcoholic filtrates 



N 

 titrated with , baryta 



solution ; the number of 

 cubic centimetres used 

 gives the Poleiiskc figure. 



This method has been 

 investigated liy many 

 observers, and it is found 

 that the specification of 

 the method is not quite 

 sufficient to allow of 

 absolutely concordant re- 

 sults being obtained. The 

 iiuthor's investigations lead 

 him to conclude that a 

 \er>- important factor, the 

 temperature of the air 

 around the flask, and the 

 rate of conduction through 

 the walls of the flask and 

 bulb tube is left to chance, 

 and he, therefore, proposes 

 to support the flask on a 

 piece of asbestos cardboard 

 in which a, hole •"> cm. in 

 diameter is cut, and to 

 surround the flask with a 

 vessel in which water is 

 boiled (see Fig. 45). Using 

 this apparatus, it is found that with butters the length of time 

 of distillation can be varied to a considerable extent without 

 ;if!ecting the results, but with coco-nut oil the time given should 

 be adhered to. 



21 



Fig. 45. — Steam Jacket. 



