214 



SCIENCE 



[Vol. LV, No. 1417 



filters is a violent agitation wHch may cause pre- 

 cipitation requiring re-filtration. Gives methods 

 of treating liquids by pasteurizing, chilling or 

 settling. Mentions filtration of glue and gelatine. 



AtHns-Shriver automatic filter press: H. D. 

 AtkIns. This apparatus is a modified form of a 

 round, center-feed filter press. A shaft passes 

 through the center openings, on which is mounted 

 plows, one in each chamber. The press is mount- 

 ed on trunnions and is filled in the vertical posi- 

 tion. Wlien filled the shaft is rotated and the 

 plow by moving in a spiral manner peels off the 

 cake from the chambers. The cake pieces fall 

 out of the press through the central openings. 

 The plows do not remove all the cake but leave 

 a thin layer on the cloths. If it is desired to 

 remove this layer it may be sluiced off. For 

 assembling and clothing the press is swung into 

 the horizontal position. Washing may be done 

 in the press. Claim is made that this press saves 

 wear and tear on cloths, saves labor, washes 

 thoroughly, and is well adapted to arrangements 

 to carry away cake. This type of press costs 

 more than the ordinary filter press per unit of 

 filtering area. 



Vallez rotary filter: H. A. Vallez. This appa- 

 ratus consists of a cast-iron cylinder so made that 

 by removing bolts it can be split lengthwise dis- 

 closing a hollow shaft on which is mounted the 

 filter leaves. Filtrate from leaves is drawn away 

 through center of shaft. When cylinder halves 

 are bolted together the material to be filtered is 

 pumped into the interior under pressure, causing 

 filtrate to issue from shaft. Filter surfaces may 

 be sluiced off. Extra shafts with leaves may be 

 kept to facilitate repairs. Leaves are spaced 

 2%, 3 or 6 inches apart. A screw conveyor at 

 bottom of cylinder removes the solids, which drop 

 off the leaves when pressure is relieved or a back 

 air pressure appUed. Claim is made that the 

 rotation of leaves while filtering causes even depth 

 of solids, indicating uniform washing. Used in 

 sugar factories. 



Centrifugal filters: H. C. Beckman. There 

 are two classes of centrifugal filters, those in 

 which the drum is perforated and those in which 

 the drum is imperforated. The first class is used 

 largely in sugar factories. Experiments have 

 been made in which filter paper or cloth is used 

 over perforations. Has no advantage over ordi- 

 nary pressure filter and several disadvantages. 

 Centrifugals of the second class use filter paper 

 and act in a measure as a self cleaning filter due 

 to the fact that the solids are discharged from 



the discs by centrifugal force. Due to this fact 

 small areas have large capacity. A disadvantage 

 is the smallness of size. A ten-inch drum eight 

 inches high with twenty seven-inch filter plates 

 operating at 6,000 E.P.M. is the largest size 

 found commercially practical. Costly liquids like 

 physiological serums, expensive varnishes, etc., are 

 handled by centrifugal filters. Maintenance and 

 upkeep are nominal. Largest size requires about 

 two H.P. and about four square feet floor space. 

 Modern leaf type filters: Egbert C. Campbell. 

 Description is made of Kelly and Sweetland 

 leaf filters. Operating instructions for complete 

 cycle are given. Washing is effected by stopping 

 formation of cake while there is yet space be- 

 tween adjacent leaves. Eighty-five to 125 per 

 cent, of the weight of discharged cakes is 

 required for complete washing. A disc filter of 

 the continuous suction type in which discs are 

 mounted on a rotating shaft which allows them 

 to dip into the mixture to be filtered is described. 

 Pressure disc filters are suitable for handling 

 sludges. Containing from less than one per cent, 

 of suspended solids to the highest per cent, of 

 solids which can be conveniently pumped and 

 drained from filter. By use of Kisselguhr col- 

 loidal or gummy solids may be handled. Suction 

 disc filters are recommended for sludges contain- 

 ing over 10 per cent, of comparatively free filter- 

 ing solids wherein a cake of greater than one 

 fourth inch thickness may be built in from one 

 to eight minutes. Average capacity of suction 

 filters is from 300 to 700 pounds of dry solids 

 per square foot filter area per 24:-hour day. Data 

 is given regarding size of air and sludge pumps for 

 pressure or suction disc filters, also water required 

 for sluicing. When suspended particles are soft 

 and compressible the plate and frame filter will 

 produce a drier cake than leaf filters. Claims 

 leaf filters have lower cloth consumption than 

 plate and frame filters. 



Oliver continuous filters: H. A. Morrison. 

 (1) Types manufactured — ^being a brief descrip- 

 tion of the individual kinds made. (2) General 

 principles involved — covering the use of the con- 

 tinuous vacuum filter. (3) Characteristics to be 

 considered in filter applications. (4) Uses — 

 with generalized statement of the more important 

 fields of operation and special description of the 

 unusual problems we have solved. (5) Installa- 

 tion and operating costs — showing complete 

 installation and operating costs in detail. (6) Ad- 

 vantages — realized by use of continuous vacuum 

 filters as compared with plate and frame presses 



