THE CLARIFICATION OR DEFECATION OF THE JUICE. 



In experiments made by the writer limed juices and limed and sulphured 

 juices exactly duplicating factory conditions gave the same weight of precipi- 

 tate, and the writer does not believe that it can be claimed that sulphuring 

 gives an increase to the purity of the juice above that due to the juice of lime. 

 Yery different methods of sulphuring juices are in vogue ; in Louisiana it is 

 usual to sulphur the cold juice until the acidity is from 3 c.c. to 5 c.c. 

 N/10 acid per 10 c.c. of juice; lime is then added until the juice is very 

 slightly acid. In Java, according to Prinsen Geerligs, the raw juice is limed 

 with about twice as much lime as is indicated as necessary by the saccharate of 

 lime test (supra) ; afterwards the juice is sulphured until only a faint red 

 colouration is afforded by phenolpthalein. In Mauritius, where white sugars 

 are made, it is general to sulphur first and lime afterwards, but in Demerara, in 

 the manufacture of Demerara crystals, the juice is generally limed before 

 sulphuring. 



ir 



FIG. 146. 



In the writer's opinion it is not of much moment whether lime or sulphur 

 be used first, as long as the following points are observed : 



1. Heat should not be applied to a juice in the presence of a notable 

 excess of either reagent. 



2. The result of the combined treatment should be to obtain a juice 

 almost exactly neutral. 



In burning sulphur it is of great importance that the air be dry, else a part 

 of the sulphur burns to sulphuric acid, which not only is of no use but is a 

 cause of the deposit of scale and of the corrosion of the valve seatings in the 

 vacuum pumps. 



Two classes of sulphites exist, both of which may be present in limed 

 and sulphured juice : the normal neutral, sulphites of the formula M 2 S0 3 



249 



