THE CLARIFICATION OF FRUIT JUICES. 17 



SIMPLE METHODS FOR USE WITHOUT SPECIAL EQUIPMENT. 



In the absence on the market of any suitable small-capacity press 

 adapted to the handling of juices with cliatomaceous earth, some time 

 was devoted to the working out of methods by which the small oper- 

 ator without special equipment could avail himself of the advantages 

 offered by the use of earth. The purpose in view was to devise an 

 arrangement in which filtration would occur through a layer of earth 

 which could be kept from clogging. Clogging can be effectively pre 

 vented by keeping the mixture of earth and liquid thoroughly agi- 

 tated, thus securing the constant renewal of the filtering surface by 

 deposition of the solid particles of earth in mixture with the amor- 

 phous suspended material of the juice. Without such provision for 

 agitation the larger particles of earth would quickly come down, after 

 which clogging by the amorphous slimy matter arrested at the surface 

 would soon occur. It was necessary also to make provision for the 

 easy and quick cleaning of the filter or the renewal of the filtering 

 layer. 



A LABORATORY FILTER. 



A very simple arrangement meeting these requirements and using 

 a compact layer of earth as a filtering medium has been in use in this 

 laboratory for some time. It yields a permanently clear filtrate at a 

 satisfactory rate and is readily cleaned when necessary. In the first 

 small filter made for use in the laboratory, a piece of 100-mesh nickel- 

 wire gauze was cut to fit as closely as possible into a large Buchner 

 funnel. A quantity of diatomaceous earth was made up into a thick 

 paste with water, spread upon the gauze in a layer 2 to 3 cm. thick, 

 packed under gentle suction, and washed with water until earth 

 ceased to come through, care being taken to keep the surface of the 

 layer of earth as smooth as possible. Filtration was then begun. The 

 juice to be filtered was mixed with diatomaceous earth, stirred thor- 

 oughly, and immediately poured on the filter. Care was taken to re- 

 peat the stirring of the liquid every time the filter was refilled. When 

 the formation of a layer of slime over the surface materially reduces 

 the rate of filtrafcloii, the filter is allowed to empty itself, a thin film 

 of earth carrying with it the gummy deposit is removed with a spatula 

 or similar instrument and stored for revivification by burning, and 

 filtration is resumed. By making the layer of earth 2 to 3 cm. thick 

 at the outset and packing it firmly, this treatment can be repeated al- 

 most indefinitely, as the material which causes clogging is practically 

 wholly arrested at the surface, penetrating at most only a millimeter 

 or two into a properly packed disk. 



