88 BULLETIN 13870, U. S. DEPARTMENT OF AGRICULTURE 
It is preferable to install at least two filters, so that the filtration may 
be continuous, one remaining in use while the second is being dressed. 
On this basis a plant grinding 150 tons of cane per 24-hour day would 
install two 600-square-foot filters. x 
This method of clarification requires a somewhat greater outlay of 
capital and slightly greater operating expense than is necessary when 
the simple process of skimming and concentrating in open evaporators 
is employed. Its advantages are as follows: (1) A product of greater 
clarity is ordinarily obtained; (2) the capacity of the evaporators can 
be increased, for it is not necessary to retard the evaporation as is at 
present the case in order to permit proper skimming; (3) the yield of 
sirup can be somewhat increased, owing to the iact that all the 
scums and dregs are obtained in a firm compact mass, instead of in 
a thin ‘‘mush” containing a large proportion of juice; (4) the quality 
of the resulting sirup is more uniiorm and depends less upon the 
skill of the individual sirup maker and the care taken in skimming; 
(5) the sirup has a color which compares favorably with that of 
the leading brands of sulphur-lime cane sirup on the market. The 
flavor is considered milder and, by many consumers, more agreeable, 
lacking the somewhat tart and metallic flavor of the ordinary sul- 
phur-lime sirup. 
TREATMENT WiTH DECOLORIZING CARBONS 
By C. F. Watton, Jr., Bureau of Chemisiry, U. S. Depariment of Agriculture 
During the last few years much interest has been manifested in 
the use of vegetable carbons of high decolorizing efficiency in the 
manutacture of sugar and sirup. Manufacturers who are producing a 
poor-grade sirup because they have been grinding cane of unsatis- 
factory quality can by carbon filtration remove excessive color and 
unusually strong or objectionable flavors, which may be so pro- 
nounced as to make the sirup marketable only as a second-grade 
preduct. Sirup made in this way is lighter in color and milder in 
flavor. The typical cane-juice flavor is somewhat lessened, for 
decolorizing carbons diminish the intensity of practically all flavors. 
The net result of treatment with decolorizing carbon, however, is 
to improve the flavor of lower-grade sirups. 
The carbon may be added to the juice following defecation or after 
filtration with infusorial earth, or it may be added to the semisirup 
at that stage of the process when the sirup would ordinarily be per- 
mitted to undergo sedimentation. Two or three times the necessary 
quantity of carbon may be used during the first filtration, m which 
case the same lot may be used over again two or three times before 
it is exhausted; or the minimum quantity may be used and discarded 
after the first filtration. In the largest sirup plants, however, it is 
feasible to install apparatus for “revivifying ” the carbon, either by 
chemical treatment or by reburning, or both, after which its activity 
is practically the same as it was in the beginning. 
' ‘The quantity of carbon required for cane sirup has been found 
experimentally to vary from about 1 to 3 per cent, based on the weight 
oi solids contained in the juice or sirup to be filtered. The requirement 
varies with the quality of the sirup and the degree of decolorization 
desired. Basing calculations on a price of $0.15 per pound for vege- 
table decolorizing carbon of suitable quality, and assuming that the 
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