CANE-JUICE CLARIFICATION. 53 



by sulphites, the result may be considered as but temporary, 

 since upon exposure to air and light the product assumes a 

 darker color. Hydrosulphites should therefore be introduced as 

 late in the process as possible. Where the material in the vac- 

 uum pan is to be bleached, it is well to introduce this reagent 

 just before striking grain, thus furnishing a bright clear mat- 

 erial which will act as film over the nucleous of sucrose in the 

 grain. 



The chemical equation representing the change which takes 

 place with this reagent is as follows: 



Na, S,O 4 (sodium hydrosulphite) +O ( oxygen) +H..O (water) 

 -^2(NaHS 3 ). 



The amount to be used will depend absolutely upon individual 

 conditions, which may be ascertained only by experimentation. 

 The manufacturers of this product state that the amount of the 

 material used to that of dry sugar should be as 1 is to 10,000. 

 In the writer's experience, two or even three times this amount 

 will usually be required to give maximum results. As stated 

 before, since there is such a variance in the material to be 

 treated, each operator will be required to judge this to a great 

 extent from the condition of his product. 



In these Islands where a very low grade of open-kettle sugar 

 is still made, which sells very cheaply, attempts are often made 

 to bleach it and recrystalize in order to make a centrifugal sugar. 



While ordinary clarifying agents help to a great extent, if 

 the melted sugars are very dark from caramel and the decom- 

 position products of calcium glucosate, these reagents can not be 

 expected to give a light-colored juice. While they may improve 

 conditions somewhat, the only solution to such a problem is the 

 use of the boneblack process. 



Bluing. In the production of plantation clarified sugars, and 

 sometimes of refinery crystals made from low-grade sugars, 

 there is a thin film surrounding each sugar crystal, which has 

 a yellowish tint. It is this that gives rise to the different grades 

 of white sugars, when color test only is considered. Since this 

 yellowish tinge will give way to a lighter color when neutralized 

 with the proper shade of blue, it is a very common practice to 

 use some form of bluing usually that known as ultramarine 

 for this purpose. 



The action of this reagent is only mechanical and great care 

 must be exercised that the proper quantity is used. This must 

 be determined by trials with the different amounts of the reagent, 

 since the density of the yellowish tint is different in each case. 



The place of application will also depend very much upon con- 



