THE CLARIFICATION OF FRUIT JUICES. 19 



with the material accumulated by scraping the filter, are preserved 

 and burned for subsequent use. 



It will be seen from the foregoing description that this arrange- 

 ment gives essentially the advantages obtained by the use of molded 

 silica filtering plates, with the differences that the material used is 

 inexpensive and may be used over and over again practically without 

 loss; that there is no danger from breakage, as in the case of filter 

 plates ; that cleaning and replacement are matters of a few minutes' 

 work only; and that the filtering disks may be made of any size or 

 shape desired by the individual operator, who may readily make 

 one or more filters of any desired capacity to suit his needs. 



A FILTER FOE HOUSEHOLD USE. 



For handling small quantities of juice, such as would be put up 

 for individual household use, where a suction pump is not available, 

 very satisfactory results are obtained by gravity filtration through 

 a disk of earth. The vessel used should be a deep one, in order that 

 the column of liquid upon the filter may be heavy enough to aid 

 filtration; for this reason also the vessel should be kept full while 

 filtration is going on. A cask provided with a false bottom for sup- 

 porting the filter and a faucet placed just below it for drawing off 

 the juice serves very well. The filter disk should be made somewhat 

 thicker than would be the case in a filter operated by suction and 

 greater care must be employed to pack the earth firmly over the whole 

 surface and especially along the walls of the container. Caution 

 must be employed in filling the filter for the first time, in order not 

 to wash holes in the layer of earth ; it is well to place a wooden float 

 in the vessel and to pour the juice upon it, as the disk of a gravity 

 filter, unlike that of a suction filter, becomes less rather than more 

 compact in use. For this reason there is less choking, and a gravity 

 filter under a head of 2 feet of liquid will run at a practically uni- 

 form rate for a long period, as there is much less tendency to form 

 a compact slime layer over the surface than when suction is used. 



A FILTER OF THE JELLY -BAG TYPE. 



A device of the jelly-bag type permits quite satisfactory filtration 

 of small quantities which would not justify the making of a more 

 elaborate filter. The bag should be made of heavy closely woven 

 denim and should have the form of a rather tall cone. The seam 

 should be double and should preferably be made by machine in 

 order to guard against leakage. After wetting the bag thoroughly, 

 it should be suspended and such a quantity of earth, previously made 

 into a thin paste with water, poured into it as will practically fill it. 

 After the water has drained away the treatment should be repeated, 



