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- 

 7on. 



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

 problem was first given by Apjohn^" in i86g. It has been developed 

 especially by Browne, ^^ 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 imity. The reducing power of 

 the commoner sugars investigated b\- Browne is given in Chapter XX\T. 



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

 the rotation of v.hich is put equal to unit}'. According to Browne these 

 are : — 



Fructose. — The rotation varies so much with temperature that special 

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

 from the formula of JungHeisch and Grimbert^^ are : — 



Temper- 

 ature. 



15 

 20 

 25 

 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 h = glucose ratio of sugar B. 



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



Then ax 4- hy = 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 "\'entzke scale in 20 cm. 

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



Then A-V + B3' -= 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 dextroFe and 

 levulose and P is the equation (2). 



