56 



FRUITS AND FRUIT PRODUCTS. 



together, while in the presence of glucose the calculated polarization 

 to the left on the sugar scale is larger than the actual reading, the 

 difference depending on the amount of glucose present. The difference 

 between the calculated reading and the actual reading is marked plus 

 (+) when the former is the greater and minus (— ) when the actual 

 reading is greater than that calculated. If all the sugar in the fruits 

 were present as invert and cane sugar it would be possible to make 

 quite exact calculations, but, as has been shown in Tables Itt and 16, 

 there is often a small excess of either levulose or dextrose. This 

 is not sufficiently marked, however, to make any serious difference, 

 especially as in nearly all the fruits examined the levulose is in excess, 

 which lessens the difference mentioned above. A small difference of 

 one or two degrees either one way or the other should be disregarded, 

 as it may be caused by the slight excess of levulose or dextrose in the 

 fruit. The following table illustrates this point very plainly: 



Table 19. 

 POLARIZATION OF JAxMS NOT CONTAINTNG GLUCOSE. 



Serial 

 number. 



Per cent 



total 



sugar as 



cane 



sugar. 



Tem- 

 pera- 

 ture in 



de- 

 grees C. 



Invert po- 

 larization. 



Calculated 



invert 

 polariza- 

 tion. 



Difference. 



20446 



53.36 



18 



-13.00 



-18.7 



-H5.7 



20183 



62.95 



20 



-20. 80 



-21.4 



+ .6 



20414 



46.77 



18 



-14. 60 



-16.4 



+ 1.8 



20175 



51.47 



20 



-18. 00 



-17.5 



- .5 



21081 



60.97 



20 



-20.00 



-20.7 



+ .7 



21082 



63.01 



21 



-12.40 



-21.1 



+8.7 



20163 



67.16 



21 



-17.00 



-20.4 



+ 3.4 



20416 



43.06 



18 



-11.80 



-15 



+3.2 



20445 



51.27 



18 



-14.00 



-17.9 



+3.9 



21083 



76.61 



21 



-25.20 



-25.6 



+ .4 



20245 



62.65 



21 



-19.80 



-20.9 



1.1 



20025 



59.33 



20 



-19.00 



-20.1 



1.1 



20196 



57.85 



21 



-18.80 



-19.4 



+ .6 



20443 



67.16 



18 



-17.50 



-23.5 



+4.0 



20589 



66.58 



20 



-23. 00 



-22.6 



- .4 



20968 



60.05 



20 



-18.80 



-20.4 



+ L6 



20448 



46.28 



18 



-13.20 



-16.2 



+3.0 



20181 



57.82 



20 



-19.40 



-19.6 



+ .2 



20967 



59.54 



20 



-19. 80 



-20. 2 



+ .4 



20179 



60.75 



20 



-18.30 



-20. 6 



+2.3 



20421 



36.58 



18 



-10.00 



- 12. 8 



+ 2.8 



20423 



r)0.60 



18 



-17.50 



-17.71 



+ .2 



20591 



55.38 



20 



-18.05 



-18.8 



+ .75 



20182 



66.72 



22 



-22.80 



-22 



- .8 



20590 



69.14 



20 



-21.50 



-22.5 



+2.0 



P0LARIZ.\T10N OF JAMS CONTAINING GLUCOSE. 



20166 

 20165 

 21021 



57. 45 

 59.08 

 66.16 



- 7.70 



- 3.80 



- 1.60 



-19.5 



-20 



-22.5 



+ 11.8 

 +16.2 

 +20.9 



