58 



FEUITS AND FRUIT PRODUCTS. 



Table 20 — Continued. 



POLARIZATION OF COMMERCIAL JELLIES CONTAINING NO GLUCOSE. 



Serial 

 number. 



Per cent 

 total 



sugar as 

 cane 

 sugar. 



Tem- 

 pera- 

 ture in 

 degrees 



Invert 

 polariza- 

 tion. 



Calculated 



invert 

 polariza- 

 tion. 



Difference. 



Polar- 

 ization 

 at 86°. 



20023 



57.83 



20 



-17.9 



-19.8 



+ 1.9 





20226 



60.47 



20 



-22.3 



-20.5 



- 1.8 





21062 



53.75 



20 



-20.6 



-18.2 



- 2.4 





19890 



56.35 



20 



-18.1 



-19.1 



+ 1.0 





20024 



57. 26 



20 



-18.7 



-19.4 



+ .7 





20169 



62.99 



20 



-21.3 



-21.3 



0.0 





20170 



62.93 



20 



-20.0 



-21.3 



+ 1.3 





20180 



66.95 



20 



—22.3 



-22.7 



+ -4 



20210 



61.80 



20 



-22.0 



-21.0 



- 1.0 





20214 



52. 50 



20 



-18.2 



-17.9 



- .3 





20184 



61.63 



20 



-19.2 



-20.9 



+ 1.7 





20189 



64.53 



20 



-21.9 



-21.9 



0.0 





20246 



73.31 



20 



-24.8 



-24. 9 



+ .1 





21084 



73.39 



20 



-24.1 



-24. 9 







20173 



58.79 



20 



-19.8 



-19.9 



+ .1 





20185 



60.93 



20 



- 8.8 



-20.7 



-M1.9 





20188 



67.31 



20 



-20.8 



-22.8 



4-2.0 





20172 



61. 52 



20 



-17.6 



-20.9 



-t- 3.3 





20186 



60.34 



20 



-16.8 



-20.5 



+ 3.7 





POLARIZATION OF JELLIES CONTAINING GLUCOSE. 



20213 



51. 55 



20 



- 5.35 



-17. 55 



+12.20 





20966 



64.59 



20 



- 4.00 



-21. 95 



+17. 95 





20212 



49.57 



20 



- 5.00 



-16.86 



+11.86 





20211 



51.76 



20 



- 4.00 



-17. 60 



+13.60 





20185 



60.93 



20 



- 8.80 



-20. 70 



+ 12.90 





Sample 20185 is especially to the point. It has an invert reading 

 of —8.80 and no dextrin was found by fermentation, but the differ- 

 ence of +12.90 indicates the presence of a dextrorotatory sugar, in all 

 probability dextrose. It is in such cases that the method of compari- 

 son shows the great value of polarization after inversion for the detec- 

 tion of a small amount of added dextrose which may not contain enough 

 dextrin to be detected by the fermentation process. 



The polarization after fermentation with yeast, by which all the 

 sugars are removed, is approximately zero and does not vary more 

 than =h0.3° in the case of products which contain no glucose, but 

 in the glucose products the right-handed polarization of the dextrin 

 is unchanged. Great care must be used, however, to secure com- 

 plete fermentation or ver}^ erroneous results will be obtained. Dex- 

 trose is more easily fermented than levulose, so that a zero reading 

 could be obtained even though a considerable amount of dextrin were 

 present, the left-handed reading of the levulose neutralizing the right- 



