THE DETERMINATION OF CANE SUGAR 523 



with kieselguhr or alumina cream ; where, however, the sucrose is especially 

 sought, more disturbing elements will be eliminated by the use of basic lead 

 acetate. The principles discussed in the chapter on the Determination of 

 Reducing Sugars are equally applicable here. 



Although quite logical and academically correct, this method does not 

 seem to have been subjected to a critical survey. Some careful analyses 

 of cane juices once made by the writer gave such discordant results as to 

 lead to the supposition that some disturbing factors enter into the determina- 

 tion. 



The Separation of Sugars in Mixtures. The method of solution of this 

 problem was first given by Apjohn 90 in 1869. It has been developed 

 especially by Browne, 91 whose treatment is followed here. 



1. The reducing power of the sugars is expressed in terms of glucose, 

 the reducing power of which is put equal to unity. The reducing power of 

 the commoner sugars investigated by Browne is given in Chapter XXVI. 



2. The optical rotation of the sugars is expressed in terms of cane, sugar, 

 the rotation of which is put equal to unity. According to Browne these 

 are : 



Cane Sugar . . . . . . i -ooo 



Glucose . . . . . . . . o -793 



Galactose . . . . . . 1-21 



Arabinose . . . . . . 1-571 



Xylose . . . . . . . . o -283 



Fructose. The rotation varies so much with temperature that special 

 numbers have to be calculated for each temperature. The factors calculated 

 from the formula of Jungfleisch and Grimbert 92 are : 



CONCENTRATION. 



Temper- i per 2 per 3 per 4 per 5 per 10 per 25 per 



ature. 



15 

 20 



25 V. 

 30 



Let x = per cent, of a given sugar A. 



Let y = per cent, of a given sugar B. 



Let a = glucose ratio of sugar A . 



Let b = glucose ratio of sugar B. 



Let R = per cent, of reducing sugars as dextrose. 



Then ax + by = R (i) 



Let A = polarization factor of sugar A. 



Let B = polarization factor of sugar B. 



Let P = polarization of mixture, i.e., reading in Yentzke scale in 20 cm. 

 tube for 26 grms. of sugar in 100 c.c. 



Then Ax + By = P (2) 



Suppose, as is the most general case, that the mixture is one of cane sugar, 

 glucose and fructose. The cane sugar is determined by the process of double 

 polarization. The difference between the value of the double polarization 

 and the single polarization is the sum of the polarization of dextro?e and 

 levulose and P is the equation (2). 



