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 
