CANE JUICE 31 



the sugar cane, one crystallizable and two called 

 " uncrystallizable." These are only rough and ready 

 expressions for which more accurate words have now been 

 substituted. But an explanation of the difference 

 between the three kinds of sugar, and of their proper 

 names, requires a brief preliminary description of the 

 way in which the quantity of these sugars in cane juice, 

 or any other sugar solution, is determined. 



The polariscope is an interesting instrument, and its 

 use in every sugar factory or refinery, and also in every 

 commercial transaction in raw sugar, is now universal 

 and essential. Its construction is based on two facts. 

 The first is that when light passes through certain 

 crystals, calc spar for instance, if the crystal be properly 

 adjusted the light is divided into two rays one of which, 

 has become " polarized." This means that the light 

 ceases to be diffused equally in all directions, but only 

 shines in one plane. The second fact is that if this 

 ray of polarized light be passed through a solution ol 

 crystallizable sugar its plane will ba deflected to the 

 right. 



The business of the polariscope is to measure the 

 extent of this deflection, and thus detect the quantity 

 of sugar contained in the solution, a very ingenious and 

 complicated process. The general facts can, perhaps, 

 be given without too many technicalities. If light 

 were made to pass through a properly adjusted crystal 

 and thus converted into a polarized ray, and if this 

 ray were then intercepted by another similar crystal, 

 similarly adjusted, the polarized ray would pass freely 

 through the second crystal. But if, between the two 

 crystals, were inserted a tube containing a solution 

 of sugar the light would no longer pass through the 

 second crystal because the plane of the ray would have 

 been deflected by the sugar. The second crystal 



