JAMS. 



57 



The pure fruit jams prepared in the hiboi'atory for coinpari.soii and 

 those commercial products that contained no glucose are arranged 

 first. The difference between the calculated and determined polariza- 

 tion is, as a rule, less than 3^. Among the jams of known origin 

 there are three exceptions to this, the maximum being +5.7 on apple 

 jam 20446. The commercial goods which would ordinarily be passed 

 as free from glucose afford one exception, and this is probably due 

 to the addition of a small amount of commercial dextrose which 

 contained no dextrin, or possibh^ to the use of cane sugar adulterated 

 with dextrose. There is said to be on the market at present cane 

 sugar mixed with cr3^stallized dextrose, often as high as 20 per cent of 

 the latter being present. In some cases this is also mixed Avith sac- 

 charin in order to secure the desired sweetening power. The value of 

 this calculation is brought out very plainly when these results are 

 compared with those o))tained with the three samples of jam which 

 have a minus polarization but which contain a small amount of glucose, 

 viz, 20166, 20165, and 21021, in which the minimum difference between 

 the calcidated and determined polarizations is +11.8 and the maxi- 

 mum +20.9. 



In pure jellies the agreement between invert polarization and that 

 calculated as indicated above is even more striking than in the case of 

 jams, the maximum difference being 3.7^ while as a rule the difference 

 is not more than 1.5^. The five commercial jellies containing small 

 amounts of glucose shoAV a minimum difference of +11.86° 



Table 20. 



POLARIZATION OF JELLIES MADE IX LABORATORY. 



Serial 

 number. 



20405 

 20410 

 20405 

 20412 

 20435 

 20437 

 20434 

 20436 

 20433 

 20404 

 20409 

 20411 

 20407 



Per cent 

 total 



sugar as 

 cane 

 sugar. 



52. 79 

 55. 81 

 56.85 

 61.19 

 55.80 

 66.27 

 64.90 

 64.71 

 77.73 

 72. 25 

 40.91 

 i8.28 

 64.41 

 61.92 



Tern- ^ 



pera- Invert 

 tare in • polarlza- 

 degrees tion. 

 C. 



-20.6 

 -20.1 

 -19.0 

 -18.9 

 -20.1 

 -23.1 

 -23.0 

 -26. 2 

 -26. 1 

 -24.3 

 -12.8 

 -17. S 

 -22. 6 

 -17.9 



Calculated 

 invert 

 polariza- 

 tion. 



22.6 



Difference. 



Polar- 

 ization 

 at 86°. 



- 2.2 



-L2 



- .6 



0.0 



+ .9 



0.0 



+ 2.5 



+ .2 



- .6 



- .4 



+ .1 



o 



- .2 



- .6 

 -L8 



- 3.4 



+ 1.1 



0.0 



+ .9 



-0. 6 



+ 1.5 



0.0 



- 1.0 



0.0 



- .1 



-0.6 



+ 2.7 



4-2.2 



