CANE SUGAR. 



Clarification for White and Yellow Sugars. The clarifi- 

 cation of juices for the manufacture of these sugars differs from that used 

 when making refining crystals in that the action of sulphurous acid is essential, 

 and that juices are boiled with a slight acid reaction ; in addition much greater 

 care is taken to remove suspended and floating foreign matter from the juices. 



In Demerara the process followed is as under : 



The raw juice is limed cold and sulphured generally in a * sulphur 

 tower,' Fig. 144> the appearance of the juice very pale yellow forming a 

 guide to the operator of the efficacy of the treatment ; the juice now has an 

 acidity of about 5 c.c. - 7 c.c. N/10 acid per 100 c.c. of juice, phenolphthalein 

 being used as indicator. After passing through a heater and settling, the 

 partially clarified juice is run into vessels of about 1000 gallons gross capacity 

 in which are arranged steam coils ; around the edge of these vessels is 

 arranged a gutter. These vessels are known as eliminators ; the juice is made 

 to boil, and the scum that rises to the surface is brushed off with wooden tools 

 into the gutter; to the juice in the eliminators phosphoric acid is added, the 

 acidity now lying from 12 c.c. - 20 c.c. N/10 acid per 100 c.c. of juice. This 

 method of cleaning juices is most thermophagous, and at best much inferior 

 to the effect obtained by the use of mechanical or sand filters ; results quite 

 equal to those obtained by eliminators may be obtained by straining the juice 

 through fine copper gauze of 120 meshes per linear inch. In the manufacture 

 of white sugars in Mauritius a similar process is followed, except that the 

 acidity of the finally tempered juice is considerably less, and is about 8-12 

 c.c. N/10 acid per 100 c.c. of juice. 



In the writer's opinion the manufacture of fancy sugars is largely a 

 question of the acidity of juice in connection with the colour reactions of cane 

 juice, which, having an important bearing on the matter, may be mentioned 

 here. 



Use of Hydrosulphite. About 1904 the manufacture of staple 

 hydrosulphites became possible, and they were introduced into the dye indus- 

 try, and thence, as decolorizing agents, into the sugar industry. The sodium 

 salt appears under the trade name of ' Blankit,' and the calcium salt under 

 that of 'Redos.' 



Hydrosulphites are very powerful reducing ageuts, and act under the 

 equation 



Na 2 S 2 4 + 0+ H 2 = 2NaHS0 3 . 



In the cane sugar industry they find an application in the bleaching of 

 juices and syrups in the manufacture of direct consumption sugars. 



In connection with their use it has been observed that after juices and 

 syrups have been bleached they become darkened on exposure, and it is usual 

 to introduce the hydrosulphite dry into the vacuum pan. A quantity of 



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