Sugar Producing Plants. 467 
various kinds and shapes. This was always a most unsatis- 
factory way, and has been entirely superseded by what 
is called diffusion. Wherefore, instead of being rasped, 
the roots are sliced up into long, narrow slices and run 
by suitable means into an apparatus called a diffusion 
battery. This consists of a number of cylindrical iron 
vessels, holding each about one ton of cut beets and com- 
municating with each other by means of valves and piping. 
In it the slices are, so to speak, soaked out with hot water, 
passing from one to the other. It is not, however, a mere 
solution that takes place but a curious phenomenon known 
to chemists as osmosis. 
This may be described as follows: If you have a vessel 
divided into two parts by a porous membrane such as parch- 
ment, and in one part water, while in the other there 
is a solution of crystallizable and uncrystallizable salts 
,together, the crystallizable ones will pass through the 
membrane into the water on the other side, while the others, 
or colloid ones, as they are called, will not. This is what 
takes place in the battery. The long, thin slices of beet 
are placed in water of a particular temperature, and the 
cell walls of the root act as the membrane, allowing the 
sugar, which is crystallizable, to pass through into the water 
while other matters remain behind. Unfortunately there 
are other crystallizable matters besides sugar, and these go 
through also, and the broken cells of course give up all 
their contents to the water. So the resulting solution is 
still impure enough, but it is much purer than the liquor 
obtained in the old way, and the process is more rapid. The 
process is a continuous one, the liquor being passed from 
one cell to another until it has passed through ten or eleven, 
when it is drawn off. One end of the battery is continually 
discharging the liquor and the other the exhausted slices, 
which latter are pressed and sold for cattle food, while the 
liquor is further treated. It is very thin, black in color, 
and quite opaque. It would be quite possible to boil it 
down now to athick syrup and let it crystallize out, but the 
result would be black sugar, and very little of it, so it must 
