Sugar-Making 263 



presses. As soon as the frame is full, the lime cake is 

 washed by passing water through it till the sugar-content 

 of the cake has been sufficiently reduced. The press is 

 then opened and the cake removed and disposed of in the 

 manner discussed in Chapter XII. A second filtration 

 is usually practiced in order to remove any solids that 

 may have gone through the first time. Later, the juice 

 is again treated with a little lime and with carbon 

 dioxid to reduce further the impurities, after which it 

 receives the third filtering. 



In most sugar houses, the juice is treated with sulfur 

 fumes before it is concentrated, although sometimes con- 

 centration precedes this process. The object of treating 

 with sulfur is to reduce the alkalinity caused by the lime, 

 and to remove additional impurities. The sulfur also has 

 a bleaching action, removing color from the liquid that 

 might be carried on to the sugar. The sulfur fumes are 

 obtained by passing air over burning sulfur which yields 

 sulfurous acid. After being sulfured, the juice is passed 

 through special filter presses after which it is ready for 

 evaporation. 



EVAPORATION 



During the processes of purification the juice contains a 

 large quantity of water which was used to extract the 

 sugar in the diffusion battery. This must be evaporated 

 before the sugar will crystallize. The first beet factories 

 did this evaporating in open pans and as a result did not 

 secure a good quality of sugar. The heat required to 

 evaporate water rapidly at ordinary atmospheric pres- 

 sure is so high that sugar is likely to be charred. For this 



