THE CLARIFICATION OR DEFECATION OF THE JUICE. 



maintained, the juice may be heated to a maximum temperature of no more 

 than 130 P., the further rise in temperature required being obtained by a 

 juice heater as described above. 



The method whereby juices are heated with extra steam taken from the 

 evaporators is described in a subsequent chapter. 



Determination of Lime required for Clarification. The 



lime is usually applied as a cream standing about 20-25 Brix, the quantity 

 required being determined by one of three methods : 



1. The raw juice is tested in the laboratory, and from the result the 

 amount of lime required per clarifier is obtained. When working on these 

 lines frequent tests should be made. 



2. To a clarifier half full of juice an amount of lime approximately that 

 which experience has shown to be necessary is added, and the reaction of the 

 limed juice to litmus paper observed. According to ;the reaction the same, 

 more, or less lime is added when the clarifier is full. Working in this way the 

 proper amount of lime required for a clarifier is soon found. 



3. Instead of using litmus paper, the limed juice is filtered into a test 

 tube, and to the clear filtrate a drop of a solution of lime in sugar is added. 

 The formation of a precipitate indicates the necessity for more lime, no preci- 

 pitate occurring with an overlimed or exactly tempered juice. 



These three methods do not give consonant results, for a juice limed so 

 far as to be just alkaline to litmus will give a further precipitation on the 

 addition of more lime ; precipitation being only complete in the presence of a 

 considerable excess of lime. 



The writer is inclined to regard clarification rather as a craft or art than 

 as a science, and pays attention to the following points : 



1. Enough lime must be used to give a faint alkaline reaction to litmus. 



2. The precipitate must settle readily. 



3. No more lime should be used than will satisfy the above requirements. 



In the writer's opinion the best control is to place a sample of the juice 

 from each tank in a four-ounce bottle, and to place each sample on a table con- 

 \enient for the observation of the employe responsible, who is guided by the 

 reaction and the colour of the juice and by the setting of the precipitate. 



Choice of Lime. The lime used should be as pure as possible ; the 

 objectionable constituents that occur in limestones are silica, alumina, magnesia 

 and sulphate of lime. The first two, if present in limestone, may form a 

 coating over the lime and prevent it slaking properly. Magnesia and sulphate 

 of lime are particularly objectionable, as when introduced into the juice they 

 are deposited, on concentration, on the tubes of the evaporators as scale. Two 

 per cent, of magnesia should be the highest quantity allowable in a lime 

 intended for use in a sugar factory. 



245 



