44 METHODS OF ANALYSIS. 



(b) Determination in materials in which of the total sugars present, 1 per 

 cent or more is invert sugar and 99 per cent or less is sucrose : 



Prepare a solution of the material to be examined in such a manner that it 

 contains 20 grams in 100 cc after clarification and removal of the excess of 

 lead. Prepare a series of solutions in large test tubes by adding 1, 2, 3, 4, and 

 5 cc of this solution to each tube successively. Add 5 cc of the mixed copper 

 reagent to each, heat to boiling, boil two minutes, and filter. Note the volume 

 of sugar solution which gives the filtrate lightest in tint, but still distinctly 

 blue. Place twenty times this volume of the sugar solution in a 100 cc flask, 

 dilute to the mark, and mix well. Use 50 cc of the solution for the determina- 

 tion, which is conducted as described under (a). For the calculation of the 

 result use the following formulas and table of factors of Meissl and Hiller : 

 Let Cu=the weight of copper obtained ; 

 P=the polarization of the sample ; 

 W=the weight of the sample in the 50 cc of the solution used for deter- 



mination ; 



F=the factor obtained from the table for conversion of copper to invert 

 sugar ; 



~2-=approximate absolute weight of invert sugar =Z; 

 ZX^y-=approximate per cent of invert sugar=y; 



p , =R, relative number for sucrose; 



100 R=I, relative number for invert sugar; 



CuF 

 yy =per cent of invert sugar. 



Z facilitates reading the vertical columns ; and the ratio of R to I, the hori- 

 zontal columns of the table, for the purpose of finding the factor (F) for cal- 

 culation of copper to invert sugar. 



Example. The polarization of a sugar is 86.4, and 3.256 grams of it (W) 

 are equivalent to 0.290 gram of copper. Then : 



Cu0.290 



100 P 8640 951 _ R 

 == 



100-R=100-95.1=I=4.9 

 R : 1=95.1 : 4.9 



By consulting the table it will be seen that the vertical column headed 150 B 

 Is nearest to Z, 145, and the horizontal column headed 95 : 5 is nearest to the II 

 ratio of R to I, 95.1:4.9. Where these columns meet, we find the factor 51.2 jj 

 which enters into the final calculation : 



. 

 F 0.290X51.2 =456 ^ ^ ^ 



