THE EXTRACTION OF JUICE BY MILLS. 



By dividing the weight of juice obtained by the weight of juice in the 

 cane, i.e., by 1 -/, the sugar extracted per unit of sugar in the cane would be 

 obtained, provided the juice were of uniform composition. 



As was originally pointed out by the late Mr. Francis, formerly Govern- 

 ment analyst in British Guiana, the residual juice in megass is of considerably 

 less sugar value than that first expressed by the mills. The following figures 

 obtained by the writer using a small hand mill will give some idea of the 

 relationship existing between expressed and residual juice : 



Sugar per One part 



Percentage cent, in Sugar per residual equal 



of juice expressed cent, in to parts of 



expressed. juice. residual juice. expressed juice. 



74-77 . . 17-34 .. 15-36 . . -885 



73-69 .. 17-47 15-20 .. -870 



70-46 .. 17-31' .. 14-35 .. -829 



65-75 .. 16-43 .. 12-50 .. -762 



68-14 .. 16-49 .. 14-63 .. -887 



70-63 .. 16-11 .. 12-74 .. -791 



66-04 . . 16-69 . . 13-73 . . -824 



70-41 .. 16-07 .. 13-17 .. -819 



7593 .. 14-86 .. 12-38 .. -833 



73-82 .. 13-99 .. 10-73 .. -767 



72-08 .. 13-44 .. 11-46 .. -853 



69-54 .. 12-88 .. 10-97 .. -852 



69-38 .. 17-75 .. 14-02 -789 



Mean -830 



Let the sugar value of the expressed juice be represented by unity, and 

 the sugar value of the residual juice by a ; then the sugar value of all the 

 juice in the cane is given by the expression 



m-faf(l-m] _ m + gf f gfm 



mm m 



and the extraction will be given by the formula 



m / m -\- af f afm _ m f 



m m m -f- af f afm 



If to a be given the value -85, it will be found that the extraction corres- 

 ponding to the weight of juice expressed is about 3 per cent, higher than 



that given by the formula ,-, _ ^^ extraction. 



In 1he table below is calculated the extraction obtained when canes 

 containing from 10 per cent, to 14*5 per cent, of fibre are crushed to a 

 megass containing 45 per cent, of fibre, using as a formula the expression, 



1-03 (m-f] 

 extraction = ^ - > : 



207 



