JAMS. 



57 



The pure fruit jams prepared in the laboratory for comparison 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 possibly to the use of cane sugar adulterated 

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

 sugar mixed with crystallized dextrose, often as high as 20 per cent of 

 the latter being present. In some cases this is also mixed with 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 obtained 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 calculated 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 show a minimum difference of +11.86 



TABLE 20. 



POLARIZATION <>1 .IKLLIKS MADE IN LABORATORY. 



