20 BULLETIN 1025, U. S. DEPARTMENT OF AGRICULTURE. 
if necessary, in order to cover the entire inner surface of the bag 
with an adhering layer of earth, after which water is passed through 
until the outer surface is washed free of the earth. The filter is then 
ready for use. It is well to keep the bag practically full to the top, 
not only in order that the entire filtering surface may be used, but 
also because of the more rapid filtration per unit area resulting from ~ 
the greater weight on the surface. While satisfactory clarification 
is obtained with such an arrangement, its use should be confined to 
the handling of very small quantities. 
PASTEURIZING BEFORE FILTERING. 
In the earlier experiments with diatomaceous earth, in the seasons 
of 1918 and 1919, the juices employed were in all cases pasteurized 
immediately after pressing and were subsequently stored until the 
settling out of cellular débris and heat-coagulable material had be- 
come fairly complete before attempts to clarify them were made. — 
The length of the storage period was determined by convenience and 
the pressure of other work, ranging from four weeks to nine months 
as extremes. Sedimentation was usually complete at the end of three 
weeks in the storage room, which was a room in the laboratory build- 
ing with no means of temperature control other than a steam coil 
to prevent freezing in severe weather. 
In some cases the juice, after being decanted from the sediment in 
the containers, was placed in a large vessel, thoroughly mixed with 
the earth by prolonged stirring, and allowed to remain undisturbed 
for several hours or overnight. It was then decanted with as little 
disturbance of the sediment as possible, mixed with a second smaller 
quantity of earth, and at once filtered. In other cases the juice was 
mixed with the earth, allowed to stand for 10 to 15 minutes with 
occasional stirring, and filtered without permitting settling to occur. 
As this treatment gave as satisfactory results as the other, all the 
juices dealt with in the later work were filtered as soon as convenient 
after being mixed with the earth. 
Juices treated in this manner were brilliantly clear and remained 
transparent after being bottled, pasteurized, and stored for more 
than 12 months in a laboratory room subject to wide fluctuations of 
temperature. The characteristic flavors of juices so treated are not 
injuriously affected. 
FILTRATION OF FRESHLY PRESSED JUICES. 
Success in the treatment of juices which had previously been pas- 
teurized and stored led to the hope that it might be possible to apply 
the treatment to freshly expressed juices, thus dispensing with stor- 
age and making the whole process of preserving fruit juices a con- 
tinuous one, in which pressing should be followed immediately by 
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