52 SUGAR 



proceeded to get over this difficulty by introducing 

 carbonic acid gas into the defecating pans, which pre- 

 cipitated the excess of lime in the form of insoluble 

 carbonate. The cane sugar manufacturers are learning 

 the lesson from their European competitors, and are 

 now beginning to practise, in countries where science 

 reigns supreme, as complete a system of defecation 

 by lime and carbonic acid as can be found in the most 

 up-to-date beetroot factory. 



We must skip over as lightly as possible the inter- 

 mediate processes which preceded the perfected methods 

 of to-day. The copper wall was superseded by an 

 operation completed in one vessel, where the juice was 

 heated by steam, the lime scums removed from the 

 surface and partly allowed to fall to the bottom of the 

 vessel, from which they were subsequently removed, 

 the clear juice being run off for concentration in the 

 vacuum pan. Another method was to heat the juice in 

 a special juice heater and then, when the air bubbles 

 had thus been removed, run it into the defecating pan 

 where lime was added, the lime and impurities all falling 

 to the bottom in the absence of air bubbles, and the 

 clear juice being decanted. 



In all these various processes the important point 

 is to hit off the exact quantity of lime necessary. Too 

 much lime would be worse than too little. But even 

 when exactly the right quantity is used it does not 

 remove all the impurities. Many modifications were 

 introduced, continuous defecators were invented, new 

 methods of heating the juice before entering the defecator 

 were adopted, but no really satisfactory results are 

 likely t6 be obtained until the lessons taught in the 

 beetroot factories are learned and applied. The pre- 

 liminary heating of the juice before defecation not only 

 drives out the air bubbles but. what is much more 



