THE SUGAR-CANE PLANT 



Defecation. 



Concentra- 

 tion. 



Crystallisation 

 in vacua. 



Curing. 

 Bleaeb'ng. 



Claying. 



SACCHARUM 



OFFICINARUM 



Improvement 



than by the roller system. The juice, moreover, is of greater purity owing 

 to the coagulation of the albumen. The defecation of the juice is thus 

 rendered far more simple and easy, and is eventually drawn from the 

 battery free from glucose and of a pale straw colour. 



//. Defecation and Clarification. These operations consist of various 

 stages, such as straining, heating, tempering, bleaching and filtering. 

 The most important of these is defecation or tempering with lime (see 

 Lime, p. 712) or other chemical substance, which, combining with the 

 acids liberated, as also with any carbonates that may be present, precipi- 

 tates these in the form of insoluble compounds (see Alkaline Earths, 

 p. 58). 



///. Concentration and Granulation. The purified cane-juice has 

 now to be freed of much of its water so as to allow of crystallisation. This 

 may be accomplished by heat, either in open pans (the Native method) 

 or in basins heated by steam or boiled in vacuum pans. In the last- 

 mentioned process the grain formed from syrup boiled in vacito is larger 

 and more solid than from syrups simply concentrated to crystallising 

 point in open batteries. Formerly the crystallisation was effected by 

 cold, the Chevallier process. 



IV. Curing. The last stage embraces the complete drying and the 

 whitening or bleaching of the sugar. This may be accomplished by simple 

 drainage, as in the Native process above briefly indicated. In European 

 trade, sugar simply drained of its molasses from casks placed over tanks 

 was known as " Muscovado," " grocery sugar," " brown sugar," etc. 

 The trade in this form is nearly obsolete. The claying of sugar corresponds 

 with the washing with water derived from a layer of aquatic weeds. In 

 the European method, a layer of clay used formerly to be placed over the 

 sugar, upon which water was poured. The water percolated through the 

 clay, removed the non-crystallisable sugar, the colouring matter and 

 other impurities. The sugar was thus washed and, through the removal 

 of the insoluble sugar, was in time also dried. But these and other primi- 

 tive methods have been superseded in all the larger factories by centrifugal 

 driers or hydro-extractors. There are many forms of this, but all consist 

 essentially of a cylindrical basket revolving on a vertical shaft, its sides 

 being of wire gauze or perforated metal. The basket is surrounded by a 

 casing at a distance of about 4 inches, the annular space thus left being 

 for the reception of the molasses expelled by centrifugal force through 

 the sides of the basket, when the latter revolves at a high speed. 



Improvement of Indian Industry. It would be quite possible to 

 perfect the small hand factories of India to enable them to turn out at 

 a cheaper rate than at present a much superior sugar. In many respects 

 sugar manufacture and refinement are eminently suited for the hand 

 labour and small capital of the village communities of India, but machinery 

 and chemistry the world over are depriving all such communities of 

 their handicrafts, and the salvation of the Indian sugar-manufacturing 

 industry, it is feared, must be rather looked for in aids toward the 

 establishment and encouragement of power factories, where the most 

 advanced methods and contrivances will be used, rather than in subsidies 

 to effete and wasteful crafts. Mr. H. F. Walker of Brisbane, Queensland, 

 in a most instructive communication (Bihar Sugar Comrn. Kept., 1901, 

 app. No. 5), discusses fully the system by which the industry has been 

 substantially aided in that Colony. Moreland (app. No. 4) gives many 



954 



Centrifugal 

 Driers. 



Improve- 

 ment. 



