CANE SUGAR. 



110 c.c., water added to the 100 mark and the volume completed to the. 110 

 mark with strong hydrochloric acid. After mixture the flask was placed in a 

 water bath and heated in such a way that at the end of fifteen minutes the 

 temperature had risen to 68. The flask was then removed, rapidly cooled, 

 and its contents polarized in a tube 220 cm. in length to allow for dilution. 

 Clerget found that a solution of 16-471 grms. of sugar per 100 c.c., which 

 polarized 100 in his polariscope, gave at a temperature of a reading to the 

 left of 44, the rotation decreasing '5 for every 1 rise in temperature. 



Hence followed the formula * = where s is the true percentage of 



sugar, and a and I are the readings before and after inversion referred to the 

 same concentration, and t is the temperature of the observation. 



This method of making the inversion is not now generally followed, 

 the official German instructions due to Herzfeld being as under 23 : 



The half-normal weight (13-024 grms.) is taken and dissolved in a 100 c.c. 

 flask in 70 c.c. of water, 5 c.c. of hydrochloric acid of 1-19 specific gravity is 

 added, and the flask and its contents warmed to 67 70C. and maintained at 

 that temperature for five minutes, at the expiration of which time the maximum 

 left rotation is obtained ; the flask is then rapidly cooled, its contents com - 

 pleted to 100 c.c., and polarized at a temperature as close to 20C. as possible. 

 A rise of temperature above 70C. or a prolonged heating invalidates the 

 results, and in the use of this process the directions must be exactly followed. 



Herzfeld found that the Clerget constant varied with the concentration of 

 the sugar, and constructed the following table : 



Por the half -normal weight the factor is 142-66, which is the now 

 generally accepted Clerget constant. The variation can also be expressed in 



the formula * = : -7- where i is the reading after inversion in 



141 ' 84 +To-l 



the 200 cm. tube without any correction. It will be observed that the 

 constant here given varies much from that found originally by Clerget. In the 



454 



