168 IMPROVEMENTS IN THE MANUFACTURE OP SUGAR. 
which the vacuum-pan is supplied. It has been found that 
one nitration through the bags is sufficient, provided a 
larger quantity of acetate of alumina be employed, and a 
fine copper sieve be interposed between the liquor running 
down from the blow-up pan and the head of the bag- 
filters. 
The boiling of the vacuum-pan is conducted in the usual 
manner, as are also the whole of the subsequent operations. 
In the preparation of fine liquor, to be employed subse- 
quently to what is termed the claying operation, it has 
been found desirable to use a small quantity of alumina, 
heating the syrup to which it has been added to 212° Fahr. 
for a few minutes, then adding sufficient of the solution of 
tannin, to precipitate the last traces of alumina, and of car- 
bonate of lime, to neutralize acidity ; and finally, passing 
through filter-bags. Cane and beet-root juice are treated 
with the acetate of alumina and solution of tannin for defeca- 
tion, either before the neutralization by lime and concentra- 
tion by heat, or subsequently, when the juice has-been con- 
centrated to from 20° to 28° Baume. 
The acetate of alumina is prepared in the following man- 
ner: Sulphate of ammonia is dissolved in cold water, added 
a clear solution of soda-ash, also made in cold water, added 
to it, until an alkaline reaction is produced on reddened lit- 
mus paper. The liquor is allowed to stand until the alumina 
is precipitated, the clear liquor then drawn off, and the pre- 
cipitate washed with a fresh qnantity of water, which is 
again removed, and the washing repeated until the hydrom- 
eter no longer indicates the presence of any soluble matter. 
The precipitate is taken with as little water as may be, 
and acetic acid added in successive quantities, until the 
whole or nearly all of the alumina is dissolved, avoiding 
an access of acid. The acetate of alumina acts best when 
recently prepared. 
The solution of tannin is prepared by digesting one pound 
of crushed valonia in two gallons of hot water, using the 
