THE OPTICAL ASSAY OF SUGARS. 



Specific Rotation of Bodies other than Cane Sugar, 

 Dextrose, and Levulose, occurring in Sugar Analysis. 



For convenience of reference some of these are here collected : 



Eaffinose ...... [ a ] j) 104 ' 2 t = 2Q (t = temperature.) 



Maltose ...... [a] * = 140-375 -01837^ '095 



(p = per cent, of material.) 

 Isomaltose gallisin . . c= 10-60 [a] 2 ? = 82-76 



e= 27-29 L a ] 2 ? = 80 * 10 



c 54-58 [a] 20 = 77-32 

 Lactose ...... HJ)~ 52 ' 5 t = 20 



Mannose ...... [] * = 12-96 t = 20 



Galactose ..... [a] * = 83037 + -199p (-276 -0025^?) t, 



5 per cent, to 35 per cent, and t =: 4 C to 40 0. 

 Arabinose ...... [a] = 104-4 = 10 * = 18 



(c = concentration in grms. per 100 c.c.) 

 Xylose ...... WT> = 18-095 + -06986^ p = 3 to 34 



Dextran ...... [a] = 230 



Levulan ...... [] = -221 = 20 c = 5 to 30 



Xylan ........ [] = 70 to 85 



Direct Polarization. The optically active constituents of the cane 

 sugar factory consist essentially of cane sugar, of dextrose, of levulose, and of 

 small amounts of other sugars ; in many cases the combined optical effect of 

 the reducing sugars is small and may even altogether vanish, so that it is very 

 general to calculate the result of the analysis as if cane sugar was the only 

 active body present. Results so obtained are referred to as sugar from direct 

 polarization. The effect of optically active bodies other than sugars can be 

 eliminated by the Clerget process described in the next section. 



The Determination of Sugar by Cler get's Process. 



A solution of cane sugar when heated with acids is quantitatively converted 

 into equal parts of dextrose and of levulose, and a solution of cane sugar 

 originally dextro-rotatory is after such treatment found to be levo-rotatory. 

 Clerget observed that the two rotations bore a fixed ratio to each other when 

 the conversion of the cane sugar into dextrose and levulose was performed 

 under fixed conditions. His original process was as under 22 : 16-471 grms. of 

 sugar were dissolved in water, transferred to a flask graduated at 100 and at 



453 



