224 CHAPTER XIII 



consequently, nitrogenous concentrates should be supplied to 

 rectify the deficiency. 



The use of alkaline manures affects the composition of 

 cane appreciably. Within the limits of ordinary applications 

 the composition is not affected very noticeably, unless phos- 

 phates are absent in the application. 



Milling and Uses. — The cost of a modern full-sized mill- 

 ing plant is very high, in the neighbourhood of ^6500,000, 

 consequently these are usually erected and run by companies, 

 v^^ho grow the major part of the cane which they mill. The 

 smaller growers sell their cane to the mill-owners at 14s. to 

 16s. per ton. 



The cane is conveyed by belts and crushed by means of 

 rollers. About 75 per cent, of the juice is extracted, and the 

 bagasse is often used as fuel to run the mill. 



" By the usual process of sugar extraction, the juice from 

 the crushed cane is at once heated to a temjierature of 190° 

 to 200°F. to clarify it. Lime is added to the juice at the same 

 time to assist the process of clarification. Sulphur phosphoric 

 acid, and other chemicals have also been used for the same 

 purpose. The purpose of adding lime is to precipitate various 

 impurities out of the juice. After this process of clarification the 

 juice is at once filtered in large filter-presses, for the purpose 

 of removing the mud and the precipitated impurities. The 

 juice is then boiled in a multiple series evaporating apparatus 

 to the consistency of syrup. It contains in that stage about 

 55 per cent, solids in solution. The syrup is then boiled in 

 vacuum pans until it is condensed to the point where it 

 separates into crystalline sugar and uncrystallisable molasses. 

 The whole mass at this stage is called massecuite. The 

 crystallised sugar is then separated from the molasses by cen- 

 trifugals, the sugar crystals being caught on a fine wire-gauze 

 strainer, with 400 to 500 meshes to the inch, while the 

 molasses is thrown out by centrifugal force. The crystallised 

 sugar is removed from the centrifugal and at once packed for 

 export as raw sugar. 



The machinery concerned in the manufacture of sugar 

 has reached a stage of great elaboration and of striking perfec- 

 tion. The whole process is a continuous one from the time 

 the cane arrives at the mill until the sugar is sewed up in the 



