468 Canadian Record of Science. 
be first clarified. This is done in what are called defecation 
tanks, and by means of a peculiar application of lime and 
carbonic acid. As both these substances are used in large 
quantities, there is a lime-kiln always attached to the fac- 
tory, in which lime-stone or carbonate of lime is burnt and 
the resulting gas and quicklime collected. 
The defecating pans are wrought-iron tanks holding about 
700 gallons each, and provided with steam coils for heating, 
and perforated coils for the injection of the gas, which is 
sucked from the kiln by means of a large pump, and forced 
into them and up through the liquor. 
The operation is as follows:—The tank is filled about 
three-quarters full of the black liquor from the battery, 
which has previously been heated to boiling point, and a 
certain quantity of lime is added (usually about 2 per cent. 
on the weight of the beets) in the form of lime milk. This 
causes an immediate partial clarification, and the whole is 
a gummy mixture, light in color. Then the gas is pumped 
through until, by a simple test, we know that it has preci- 
pitated very nearly all the lime that was put in. This pre- 
cipitation completes the clarification begun by the lime, as it 
seems to drag down small suspended particles and coloring 
matters with it, to the bottom of the tank. The action is 
not very well understood, but the result is a very bright, 
clear liquor of increased purity. 
We now have the defecator filled with a nearly boiling 
mixture of lime and sugar-liquor, and the question is to 
separate the one from the other. This is done in what are 
called filter-presses, which are machines so constructed that 
the mass is forced into spaces between coarse cloths held 
in iron frames, so that the liquor runs out clear through 
the cloths, and leaves a thick, nearly dry, cake behind. 
The cake is thrown outside, to be used as manure, and the 
liquor passes into the next stage, which is a simple repeti- 
tion of the defecation, in which a little lime only is added 
and the gas passed through until there is but a trace of lime 
left. It is necessary to repeat the operation in this way to 
get areally good clarification. It is again filtered, and is 
