INDUSTRIAL AND ENGINEERING CHEMISTRY
January 1951
(201) Hoak, R. D.,and Coull, J., Chem. Eng. Progrees, 46,158 (1950). (202) Xarnofsky, G.,Chem. Eng., 57,No. 8,108 (1950). (203) Xarnofsky, G.,J . Am. Oil Chemists’Soc., 26,664(1949). (204) Encaide, C.R., U. 8. Patent 2,491,116(Dea. 13,1949). . , 387 (1960). (206)Klose, A. A.,et al., IND.ENO.C H ~ M42, (206) Krchma, I. J., and Schaumann, H. H. (to Du Pont Co.), U. 8.Patent 2,502,327(March 28, 1960). (207) Kurth, E. F.,Hubbard, J. R., and Gekelea, M., Leather and Shoes, 118,No. 20,22 (1949). (208) Lemoine, J. L., French Patent 940,159 (Dec. 6,1948). (209) Logan, V. R., U. 8. Patent 2,453,633(Nov. 9,1948). (210) McCubbin, K., and Ritz, G . J., Chem, I d s . , 66,354(1950). (211) McInnes, C.A., Am.Paint J., 34,No. 30,86(1960). (212) Mastin, M. G.,C h a . Eng., 57,No. 1, 100 (1950). (213) Mernke, W. W.,Holland, B. R., and Harris, W. D., J. Am. Oil Chemists’ Soc., 26,532 (1949). (214) Mukherjee, S.,and Gupta, M. L. S., J . PTW.Inst. Chemists (India), 21,45 (1949). (215) Naudet, L., In&. agr. et aliment, 66,107(1949). (218) Ode, W. H.,and Selwig, W. A., IND. ENQ. CHSM., 42, 131 (1950). (217) Othmer, D.F.,and Luley, A. H., Food, 18,81 (1949); Sugar, 44, No. 7,26 (1949). (218)Paovna. Arnold. U.9.Patent 2.485.841 (Oct. 25. 1949). (219) Pascal, M. W. (to Sherwin-Williams Co..), U. S.’Patent 2,505,139 (April 25, 1950). (220)Perez, A. (to Phillips Petroleum Co.), Ibid., 2,485,916(Oct. 25, 1949).
85
(221) Pluhacek, R., and Slavicek, E., Lis& Cukronur. 65, 125 (1949). (2221 Rotinyan, A. L.,and Drozdov, B V., Zhur. Obshchei Khim., 19. 1843_ (1949). -., _ ~ . (223) St. Clair, H. W., and Blue, D. D., U. S. Bur. Mines, Rept. Inwest. 4535 (1949). (224) Skow, M. L., and Conley, J. E., Ibid., 4649 (1950). (225) Slavicek. E.,Listu Cukrmar. 65,89 (1949). (226) Snow, E. A., and Bailey, L. F., J. Am. Leather Chemists’ Assoc., 44,737 (1949). (227)Societe des cimenta franpais, Brit. Patent 632,079 (Nov. 16, (1949). (228) Sweeney, 0.R.,and Arnold, L. K. (to Iowa State College Research Foundation), U. S. Patents 2,497,700 (Feb. 14, 1950) and 2,501,880(March 28,1950). (229) Sweeney, 0.R.,and Arnold, L. K., J. Am. OiE Chemists’ Soc., 26 697 (1949). (230)Sweeney, 0.R.,‘Arnold, L. K., and Hollowell, E. G.,Iowa State Coll. Exptl. Sta., Bull. 165 (1949). (231)Thompson, M. R.,McLeod, H. M., and Skow, M. L., U. S. Bur. Mines, Rept. Invest. 4528 (1949). (232)Trottman, C., U. S. Patent 2,489.599(Nov. 29,1949). (233) Watson, Thomas S. (to Huebach Mfg. Co.), Ibid., 2,501,460 (March 21, 1950). (234)Wittig, R.,Chem.-lag.-Tech., 22,81 (1950). (235) Yuan, H., Xuo, F., and Huang, Y . , Science and Technol. (China), 2,21 (1949). \ - - - - I -
R E C E I VOctober ~D 11, 1950.
FILTRATION mg
SHELBY A. MILLER
UNIVERSITY OF KANSAS, LAWRENCE, KAN.
given remains one of the most useful in existence. The material on filter mediums has been brought u p to date and several new filters have been added to those described. The chapter on filtration (2%) in the new textbook on unit operations prepared by University of Michigan chemical engineers is well written. More than half the chapter is devoted to mathematical correlating relationships, which include not only the conventional Poiseuille-Darcy c o n s t a n t- p r e s su r e and constantrate equations (written explicitly in terms of cake porosity) but the recent Brownell-Kats attack from the standpoint of a modified Fanning group including particle and cake characteristics. The reader is prepared for the latter approach by two preceding chapters (91) devoted to the Brownell-Katz method. Fifteen problems at the end of the chapter illustrate filterdesign calou]ations. The description of equipment is brief and includes only the best known types of filters; i t is supplemented, however, with a number of clear, chosen photographs and drawings. A superior summary of filtration in the laboratory is presented (43) in a new reference book of organic chemical technique. The extensive theoretical review and the thorough analysis of the problems posed by various instances of filtration make this chapter valuable to the engineer and plant supervisor as well as to the chemist and laboratory technician. I n the periodical literature, Heertjes (66) has prepared an excellent review of the methods of correlating and analyzing filtration data and of the nature of specific cake resistance. Authoritative and complete, clear and concise, i t is unequaled in the filtration literature. Friedel (66) has given a qualitative dis-
N e w contributions to filtration theory include an analysis of continuous vacuum filtration and a study of the resistance identified with the initial stages of cake formation. Equipment advances have been mostly in the nature of improvements: Among them are a compact high-capacity porous-metal element, a cake sluicing mechanism for precoat filters, and a tilting Alter press. Dyne1 and Hastelloy filter fabrics now are commercially available, and a new fiber, Terylene, looks promising as a filter medium material. Rotary vacuum filters have been evaluated for a variety of applications: petroleum dewaxing, sewage sludge dewatering, paper pulp recovery, and oil-waste emulsion breaking. A paper on whisky clarification excellently typifies the correct approach to filter selection. Interesting data are reported also on viscose filterability and on the refining of metals b y filtration of solid constituents from molten metal suspensions. A number of outstanding reviews of filtration theory, equipment, and methods bring the occasional user of filters generally up to date for the first time in several years.
c
,*
*
ONVENTIONAL filtration-the separation of undissolved solids from liquids by methods other than centrifugation, sedimentation, and adsorption-was the subject of more publications in the Year ending October 1950 than in m Y of several immediately preceding years. This review attempts to cover those of particular value to the chemical process industries and includes uncritical citation of many (although by no means patents which have been issued. AS in all) of the previous tmnual reviews Of this series, the scope gas clarification, centrifugal and sedimentary separation, adsorptive percolation, and biofiltration. GENERAL REVIEWS
have welcomed several new Those intereskd in unit books devoted to this field. Three are general and include filtration in their coverage. The long-awaited third edition of Perry’s “Handbook” carries a section on filtration (76) which is the same in arrangement and, to considerable extent, in content as that of previous editions. The unfortunate interval between copy deadline and publication date prevented the inclusion of the most recent advances in theory; but the summary of theoretical and empirical equations
a6
INDUSTRIAL AND ENGINEERING CHEMISTRY
cussion of hypotheses concerning the role of surface phenomena and adsorptive forces in medium plugging and filter-aid action. In addition to a very brief summary of recent advances (33), two papers have dealt with industrial filters and their selection and performance. Miller’s descriptive review (102) includes a discussion of clarifying as well as cake filters and lists most of
Vol. 43, No. 1
pendently studied the same problem, but apparently interpreted his results in a different manner. Because this reviewer only recently became aware of Ishikawa’s work and has not yet obtained a copy of his paper, he cannot report on it until a later time. Burak and Storrom (27) pursued the analogy proposed by Maloney (96) between centrifugation and filtration. They found the resistance of a centrifugally deposited cake to be considerably different from that of a cake of the same material deposited in ordinary filtration. Maloney (97) has given a more extensive review of their work. The so-called “filtration effect,” believed by some to be responsible for part of the resistance identified mith filter mediums, is the subject of two Russian papers (87, 109). EQUIPMENT
COURTESY FILTRATION ENOINEERS, INC.
Pilot Plant Rotary Vacuum Filter
the United Statesmanufacturers of filtration equipment. h.Iiessner (100) has summarized important performance and price data for the past several years; most of his information is derived from the American literature. THEORY, E X P E R I M E N T A L DATA, AND DESIGN
Further attempts have been made to characterize the action of rotary vacuum filters. Mondria (103) succeeded in analyzing a continuous filtration process a t constant pressure to arrive a t relationships which will permit easier prediction of the effects of drum speed and cloth blinding on filtration rate. His equations obviate the necessity of the abRolute evaluation of eake resistance and filter-medium resistance. The data they require for cloth blinding will be difficult to obtain, but the drum-speed data are easily available and may be simulated by use of a teat leaf. Reeves (117) considered the operation of washing a rotary-filter cake and derived expressions for the maximum amount of wash which can be applied under various conditions of solvent dilution and filtrate recirculation. Implicit in his analysis are the assumptions of negligible filter medium resistance and simple displacement of filtrate by wash liquor. He concluded that recirculation of part of the filtrate may improve washing effectiveness (with a viscous prefilt), but will do so at the expense of filter capacity. Brownell’s earlier work is applied in an additional paper (24) to the problem of prediction of air rate and temperature required for a top-feed vacuum filter-dryer. The porosity, permeability, and “residual saturation” of the a t e r cake must be known for the calculation to be made. Camp and Phillips (28) conducted a careful experimental investigation of the performance of a pilot plant precoat vacuum drum filter in the treatment of water-in41 emulsions and sludges, which shows the effect of a number of variables on vacuum filter operation. Heertjes and Haas (67) reported an investigation of the resistance of a filter fabric and of the initial layer of solids deposited upon it. The resistance of the initial solid layer, they found, is importantly affected by the concentration of the slurry from which i t is deposited, and may have the characteristics of complete-blocking filter-medium filtration, of cake filtration, or of any condition between these extremes. Ishikawa (76) inde-
Claude (42) has described the vertical-leaf precoat pressure filter and discussed briefly its use in American plants for filtering water, oil and varnish, and general chemicals. The advantages and some of the limitations of this type of filter have been summarized by one of its manufacturers (%’), a firm which has recently offered a new type of oscillating and reciprocating manifold for rapid flushing of the cake from the leaves (40). A filter press that can be tilted to combine the advantages of vertical and horizontal frame positions is now manufactured by an American company (34), and a continuous pressure filter has been invented in Russia (15). Tessmer (134) has proposed an improved drainage surface for a pulp-cell filter press. KrackIauer (89) patented a “stirring screen” to protect the filter medium in a horizontal pressure filter during mechanical removal of cake. Two patents deal with the modification of granularbed filter shells: One (101) describes an improved false bottom for drainage, and the other (148) suggests compartmentiaing the tank to permit a lower water flow rate for satisfactory backwashing. One of the manufacturers of rotary vacuum drum filters has issued a new catalog (53) which describes the construction and operation of this type of machine; the same firm offers for rental a flexible semiworks model of its filter (S8). A patent (58) has been issued covering a vacuum disk filter design which involves tangentially bounded sectors, a shape which results in more effective use of the filter area. -4novel vacuum filter comprising a band of discrete filter cells is the subject of a Dutch patent (145). Among new items of clarifying equipment are a compact package unit comprising a filter cartridge of small holdup volume and a pump (41), and an edge filter, the slots of which are formed by meshing teeth a t the peripheries of two coaxial disks (1). Other contributions to the field of clarifying equipment are principally in the form of patented improvements to filter element design. The most interesting of these are Micro hIetallic’s Surfamax and Gravitain elements (35, 99), assemblies of coaxial disks, the conical surfaces of which are of porous stainless steel. Strassheim (131) also has developed a porous-metal element, formed from corrugated porous sheet, Other inventions include a feltcovered polishing element (%), a zigzag paper or cloth element and a screen support for i t (20),and a cartridge element with a settling trap in its core for the collection of heavy suspended particles (11). Two patents (30,79) describe movable elements which are shifted automatically into a flushing position when cleaning is required. This reviewer’s attention has been directed to several foreign patents whose content is unknown but whose titles indicate that they describe filtration equipment. The subjects treated are: a concentric filter bag ( 4 4 , a filter for liquids (llS), an apparatm for filtering distillates (96), an industrial vacuum filter (110), a drum-type filter with a continuously renewed filtering surface (@), an improved scraper for removing fibrous cake from a drum filter (l14), a filter having multiple elements and automatic application of wash liquor (81), and a device for washing filtering areas of filter presses (150).
January 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY METHODS AND APPLICATIONS
*
t
The detailed investigation by Samuelson and his co-workers of the filtering properties of viscose spinning solution has continued (198-130). These authors now conclude (199) that the clogging of secondary filters is caused by gel particles extruded through the &st filter rather than by agglomeration of dispersed material after filtration. According to Kleinert and Moessmer (86),the gel which clogs filters is highly polymerized cellulose. The filterability of difficultly filterable viscose is improved by the addition of certain wetting agents (198), and is apparently independent of the presence of small amounts of calcium silicate precipitated from impurities in pulp and in mercerizing liquor (130). Wehrung (144) has commented on the importance of adequate filters t o minimize spinning interruption; filtration is not enough, however, because afterprecipitation of solute in the warm spinnerette can occur. Various arrangements of filters in series and in parallel have been devised to allow servicing without interruption of the spinning solution stream (14, G). Vosters (142), objecting to the usual procedure for determining viscose filterability, proposed an alternative constant-rate method. The use of rotary vacuum filters by the petroleum industry in solvent dewaxing processes is spreading. Kalichevsky (80) and Reeves ( 117) have discussed optimum operating conditions for such filters. Slack wax sweating can be eliminated advantageously in favor of the use of a new ingenious continuous pressure filter, according to Weber (143). The filtration of lubricating oil in situ is vital for the protection of machines, as emphasized by Vokes (140). A recent investigation (6) showed the reduction in machine wear resulting from the installation of partialflow or full-flow filters in the lubrication system. If heavy-duty oil is being used, however, the filter must be selected carefully to minimize the adsorptive removal of detergent from the oil; cellulose, cotton, and clay filters are particular offenders in this respect (3). Kipp (84), on the other hand, has proved the value of continuous by-pass filtration of transformer oil through an adsorbant to prolong oil life and inhibit sludge formation. The role of filtration in good electroplating practice has been discussed by Faint (61)and by Carr (99). Filtration may be effected by external filters (99)or by cloth or paper diaphragms within the plating cell (94,136). Filters used t o thicken or dewater paper stock have been described by several authors. Two new vacuum thickeners (4, 120) and one new continuous gravity filter (19) have been reported for this use. Kassing (82) has pointed out that papermaking itself is essentially an application of filtration and should be guided by the principles of this operation. Filtration has long played an important part in wet metallurgy. Woolf and Bethune (149) have given a detailed description of the Burt filter, a rotating batch pressure filter, and of its use in zinc leaching. Ross (124) wrote of the performance of rotary vacuum filters in handling difficultly filterable cyanide pulp, and proposed a definition of washing efficiency. Bryant (26) reported a cobalt refining process involving the filtration of precipitated metal salts. Somewhat newer is the use of filters to refine molten metals by the removal of a crystallized phase. A great deal of the pioneering experimentation on this operation was done in Germany before and during World War I1 and has been documented by Reinacher (118,119). St. Clair (197) has summarized the PBL report (119) and some additional similar work done in Canada. Miscellaneous industrial applications of filtration described in the recent literature include the straining of paint and varnish (88), the reduction of the bacterial count in milk by precoat filtration (74), the sterilization of beer by filtration through pulp sheet in a presterilized filter (lor), and the clarification of whisky (64). The latter reference is the report of a careful, thorough plant study, the object of which was to determine the most effective and economical type of filter for each of the three
87
clarification stages involved The process industries well might take its approach as a model in intelligent evaluation of equipment. Bastone and Babcock (9) have investigated the factors affecting the washing of sugar liquor from a bone-char filter. Hoover (68) has devised an ingenious method of solid-liquid separation that is in essence a filtration for which the filter medium is a mass of solid particles suspended in a liquid. WATER, SEWAGE, AND INDUSTRIAL WASTES
The processing of water and wastes, if not the chief concern of the chemical process engineer, is for him an insistent problem. For this reason and because the filtration difficulties encountered often are similar to those met in orthodox chemical processing, representative portions of the literature on the physical filtration of water and sewage are included in this review. Rapid sand filters continue to be the most popular type for water clarification. Further data from Chicago’s well publicized plant (10)and detailed data from Groton (61) have been reported. New installations are being made regularly for industrial (6)as well as for municipal water plants, and in some instances anthracite is preferred over sand as the medium (69). The use of rapid sand filters to prepare water for the rayon and beverage industries has been mentioned (66). Installations to provide industrial water in Germany (12) and in Russia (86) have been described. Ullrich (137) has discussed generally the design and maintenance of rapid sand filters. Tankard (132) has summarized difficulties encountered in (but not necessarily peculiar to) pressure filter operation for water clarification. Lane and Smith (91) found an anthracite pressure filter satisfactory for removing colloidal clay from water if activated silica pretreatment was used; their work emphasizes the importance of prefilt condition to the succem of filtration. Robinson (193) has outlined the procedure for cleaning fouled filter beds with chemical solvents, notably hydrochloric acid. Boucher (17) invented an unusual gravity water filter in the form of a rotating cylinder whose surface is the filter medium-finely woven wire (aperture dimension no greater than 10 microns). More and more sewage disposal plants are turning to vacuum drum filters for sludge dewatering (126). Certain mechanical features and corrosion problems identified with their use were discussed by Flood (64). Operating data, including filter capacity and cake moisture .content, have been reported from many different plants (77,83, 161). Mick (98) found that spray-washing the filter medium is instrumental in prolonging its life and that there is an optimum interval between washings, even when the filter is so modified that the cloth can be washed without interrupting the filtration. Richter (191)stated that the cord filter (a drum on which overlapping cords, which are the filter medium, are continuously wound and unwound) is superior to a conventional drum filter for sludge dewatering. Treated sewage effluent may be clarified by passage through a slow sand filter (141).
The paper industry’s problem of recovering fiber loss, eliminating stream nuisance, and minimizing water make-up can be reduced by clarification of white-water through sedimentation, flotation, or filtration. These three techniques have been compared and discussed (49, 69). A new vacuum filter, the Wac0 filter, is effective for white-water clarification (16). It consists of a cylindrical drum over which an endless screen belt, carrying a precoat of fiber, travels (104). Alternatively, the white-water can be clarified by coagulation and sedimentation , followed by the polishing of the supernatant in a precoat plate-and-frame press (47). The settled sludge can be dewatered successfully by an ordinary vacuum drum filter (60). The processing of wastes from an oil refinery involves the separation of oil-water emulsions which are stabilized by the presence of fine solids. Recent studies indicate that both waterin-oil (28) and oil-in-water (69,146) emulsions can be broken
88
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
and the suspended dirt removed by the uae of rotary vacuum precoat filters. Experimental data have been reported for a pilot plant filter in each type of application. FILTER M E D I U M S
Three useful summaries of the physical and chemical properties of synthetic fibers now available have appeared within the year ( I S , 69, 70). They suggest two additional candidates as material for filter fabrics: the polyester of ethylene glycol and terephthalic acid (called Terylene by I.C.I., Delvon by Du Pont), a chemically inert, extremely strong fiber; and polyethylene (made by Du Pont and by I.C.I.), also chemically inert. The latter is less likely to succeed because it is available only in monofils, from which satisfactory fabric is difficult to produce (70). Filter cloths made from Dyne1 (Vinyon-N staple, Carbide & Carbon Chemicals Corp.) are now available and are said to be superior because they not only are chemically resistant but possess a softness and body which enable them to seal a press against leakage (36). Nylon is now used not only in filter fabrics but as a re-enforcing fiber in papermaking felts (63, 116). Acidresistant filter fabrics also are made from nitrated cotton (106) and from Hastelloy B and C (Sa). New bulk mediums that have been proposed are cellulosic sponge (8) and a bulk of parallel sheets of resin-bonded cellulosic tissue, about 240 per inch of thickness, through which the filtrate may pass parallel to the sheets (158). Additions to the family of rigid porous mediums are Oilite stainless steel element8 (Sg), available in a variety of shapes and porosities, and a pressed agglomerate of spheres of synthetic resin, directions for the preparation of which have been provided by Gebert (57). Riddick (198) has presented a summary of specifications for filter sand.
Vol. 43, No. 1
been disclosed by Versa1 and Kruppe ( I S Q ) ,and tt method of cleaning such an element by use of a fused organic salt has been recommended by Budde and Potempa (96). Nikonorov (105) advised the replacement of paper by a sintered-glass element in phosphorus determinations (105). Hueckel and Pietsch (71) have given directions for the production of a collodion membrane for ultrafiltration. Laboratory procedures published which importantly involve filtration include the analysis of water for iron by hydroxide precipitation and filtration on a membrane filter ( 7 ) and the rapid determination of silica in water by precipitating i t a t such a p H as to make it readily filterable (111). Ospenson (108) reported that certain surface-active agents ndl prevent the “crawling” of nickel dimethylglyoxime precipitates and therefore will accelerate the filtration and washing of this material. CONCLUSION
The appearance of a number of up-to-date reviews and summaries of useful theory, commercially available equipment, and established methods puts the user of filters in his best position for perhaps a decade. While these general references constitute probably the most outstanding feature of the filtration literature of the past year, the period has been exceptional also in that it has produced several signififioant contributions to the further development of filtration theory and data interpretation. Equally gratifying has been the publication of a few quantitative, detailed reports from the process industry on the performance and selection of filters. These important new papers have all come from universities or from users of filtration equipment; it i s hoped that in the future more contributions from the designers and manufacturers of filters will take their place beside those from other sources.
FILTER A I D S
Diatomaceous silica is still the most popular filter aid. An industrial bulletin explains its use in water filtration (78), and a British patent describes its application in gold and silver cyanide metallurgy (78). Pernoux (111) examined diatoms with the electron microscope and found the pore diameter to be 0.5 micron. After treatment with hot 5% aqueous sodium carbonate, shown by Teichner (1%) to attack the silica appreciably. the pores were somewhat enlarged. Claude (41) emphasized the use of fibrous material, such as cellulose, as filter aids. Finely ground bagasse has been used to improve the filtration of mud from sugar cane juice (55, 147). Fibrous cellulose filter aids have been described by two 6rms that market them (13, 7 3 ) . Two special filter aids have been described: diatomaceous earth or bentonite coated with a vinyl resin (60), and insoluble inorganic salt crystals to assist the filtration of viscous liquids (116). L A B O R A T O R Y A P P A R A T U S AND M E T H O D S
Improved apparatus and methods for vacuum filtration in the laboratory have been proposed. These include adapters to permit the use of ordinary funnels and flasks for vacuum filtration (go), to prevent spattering at the funnel discharge (91), to obviate the necessity of a rubber or cork stopper in the filter flask by the substitution of a grease-sealed glass plate (93), and to allow the ready interchange of receivers between 0.5 ounce and 5 quarts in capacity (1.35). An improved Biichner funnel with a removable bottom plate (2) and a filter flask modified to eliminate the side arm in favor of a grommeted hole (18) have been proposed. Rothman (115) has constructed an all-glass apparatus for filtering and dispensing solutions in a closed system. Dubbs (46) has developed an apparatus in which an astounding number of operations-among them, filtration-can be accompliahed without the sample’s being removed. A method of constructing a sintered-glass filtering element has
LITERATURE CITED
Algemeene Kunstzijde Unie N.V., Dutch Patent 64,709 (Oct. 15, 1949).
Anon., LabOTatOTy, 20, No. 1 , 2 2 (1950). Anon., Petroleum (London), 11, 206 (1948). Anon., Svensk Pappemtidn., 53, 14-15 (1950). Anon., World’s Paper Trade Rev., 132, No. 15, Tech. Suppl., 86-8 (1949). Automobile Engr., 38, 15-20 (1948): 39, 12 (1949). Baier, C. R., Wasser, Vom, 17, 93-102 (1949). Banigan, T. F., and White, W. D., Can. Patent 458,964 (Aug. 16, 1949).
Bastone, H. J., and Babcock, A. B., Proc. Tech. Session Bone Char, 1949,149-64.
Baylis. J. R.. J . Am. Water W o r k s Assoc., 42, 687-700 (1950). Becker, 0. A., U.S. Patent 2,481,489 (Sept. 13, 1949). Belan, F. I., Stal, 8, 822-6 (1948). Bendigo, C. W., and Scott, R. C., Tertile World. 99, No. 9, 11130 (1949).
Birsch, E. T., and Silcox, W. D., U. S. Patent 2,454,124 (Nov. 16, 1948).
Bobrik, I. P., and Parfenov, E. G., Russ. Patent 69,593 (Oct. 31, 1947).
Bolin, G., Svensk Papperstidn., 52, 214-16 (1949). Boucher, P. L., U. S. Patent 2,462,604 (Feb. 22, 1949). Bretherick, L., Chemistry & Industry, 1949, 268. Breyfogle, R. H., Can. Patent 463,622 (March 14, 1950); U. S. Patent 2,476,131 (July 12, 1949). Brixius, J. K., U. S. Patent 2,479.722 (.4ug. 23, 1949). Brown, G. G., et al., “Unit Operations,” Chap. 16-17, New York, John Wiley & Sons, 1950. Ibid., Chap. 18. Brown Co., New York, “Solka-Floc ns Filter Bid,” undtited. Brownell, L. E., and Crosier, H. E., Chena. Eng., 56, No, 10, 124-7, 170 (1949).
Bryant, P. S., Inst. M i n i n g Met., Symposium o n fiefining N o n Ferrous MetaZa, 1949, 259-79.
Budde, W. M., and Potempa, S. J., Anal. Chent., 22, 1072 (1 950).
Burak, N., and St,orrow,J. A,, J . SOC.Chem. I n d . (London), 69, 8-13 (1950).
Camp, E. Q., and Phillips, C., OiZ Gas J.. 48, No. 46, 214-15, 341, 343-5 (1950).
January 1951
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0
INDUSTRIAL AND ENGINEERING CHEMISTRY
(29) Cam, K.L., Finish, 7,NO.5,29-30 (1950). (30) Carrier, W. W., U. S. Patent 2,480,320(Aug. 30,1949). (31) Chaffey, R. H., Ibid., 2,510,378(June 6,1950). (32) Chem. Eng., 56,No. 10,136(1949). (33) Ibid., No. 11, p. 109. (34)Ibid., 57,No. 1, 138 (1950); Chem. Inds., 66,96(1950). (35) Chem. Eng., 57,No. 6,152 (1950); Chem. Inds., 66,900 (1950). (36) Chem. Eng., 57, No. 7, 160, 162 (1950); Chem. Inds., 67, 102 (1950). (37) Chem. Eng. Progress, 46,No. 2,27A (1950). (38) Chem. Inds., 65,619(1949); Sewage W w k s Eng., 20,520(1949). (39) Chem. Inds., 65,776(1949). (40)Ibid., p. 937; FoodInds., 22,106 (1950). (41) Chem. Inds., 65,937-8 (1949). (42)Claude, R., Chimie & industrie, 64,48-51 (1950). (43)Cummins, A. B., in A. Weissberger’s “Technique of Organic Chemistry,” Vol. 3, Chap. 6, New York, Interscience Publishers, 1950. (44) Danil’tsev, V. A., Russ. Patent 69,259(Sept. 30,1947). (45) Davidson, H.O.,U. S. Patent 2,469,293(May 3,1949). (46) Dubbs, C. A,, Anal. Chem., 21,1273-6 (1949). (47)Ehemann, G. C.,Burnett, L. K., and Waddell, J. C., P u l p & Paper Mag. Can., 51,No. 7,107-11 (1950). (48) EllilB, K. L., Swed. Patent 126,303(Oct. 4,1949). (49) Emes, Papierfabr. Wochbl. Papierfabr., 78,176-8 (1950). ENC.CHEM.,41,1806-9 (50) Erspamer, A. S.,and Rice, W. D., IND. (1949). (51) Faint, H.W., Finish, 7,No. 6,25-6,64 (1950). (52) Faulconer, F. M., McCann, D. L., and Bedell, H. L., Pefroleum Engr., 21C,No. 12,26-32 (1949). (53) Filtration Engineers. Inc., Newark, N. J., “FE Rotary Vacuum Filters,” Bull. 103 (1949). (54) Flood, F. L., Sewagelnd. Wastes, 22,307-14 (1950). (55) Freeman, L., U.S. Patent 2,500,065(March 7,1950). (56) Friedel, F. A., Chem. Ing. Tech., 21,382-3 (1949). (57)Gebert, A.,Swiss Patent 263,031 (Nov. 1,1949). (58)Genter, A.L., U. S. Patent 2,464,223(March 15,1949). 41,1047-52 (1949); (59) Georgia, F. R., J . Am. Water W o r k s ASSOC., Water & Sewage Works, 97,223-8 (1950). (60) Goetz, A., U. S. Patent 2,508,602(May 23,1950). (61) Greenleaf, A. C., J. New Eng. Water Works Assoc., 64,97-106 (1950). (62) Gustafsson, K.F., Svensk Papperstidn., 52,210-13 (1949). (63) Hall, E. H., U. S. Patent 2,506,667(May 9,1950). (64) Harmer, D.M.,Kolachov, P. J., Smith, L. A., and Willkie, H. F., Chem. Eng. Progress, 46,203-8(1950). (65) Haywood, R. W., Jr., and Wells, B. H., J. Am. Water Works Assoc., 41,856-64 (1949). (66)Heertjes, P. M., Research (London),3,254-9 (1950). (67) Heertjes, P. M., and Haas, H. v. d., Reo. trav. chim., 68,361-83 (1949). (68) Hoover, C. O.,U. S. Patent 2,472,976(June 14,1949). (69) Horst, W. P.t., Chem. Inds., 66,521-6 (1950). (70) HONlett, F., J. TextileInst., 41,P124-31 (1950). (71) Hueckel, W., and Pietsch, H., Suomen Kemistilehti, 22B, 1-7 (1949). (72) Huntington, Heberlein and Co., Brit. Patent 633,203 (Dec. 12, 1949). (73) Industrial Chemical Sales Division, West Virginia Pulp and Paper Co., New York, “Polycel Purified Wood Cellulose,” 1948. (74) Ingelsent, H., and Storrow, J. A., Food, 19,25-6 (1950). (75) Irvin, D.F., and Bellas, H. W.. in J. H. Perry’s “Chemical Engineera’ Handbook,” 3rd ed., pp. 964-92, New York, MaGraw-Hill Book Co., 1950. (76) Ishikawa, H., Waseda Applied Chem. Soc. Bull., 19, 51-69 (1 942). (77) Jepson, C., and Greene, G., City of Manchester (England), Rivers Dep., Rept. 55 (1948). (78) Johns-Manville Celite Division, New York, “Celite Diatomaoeous Earth Powder for Economical Filtration of Water,” undated. (79) Jokel. W.. U.8. Patent 2.475.968 (Julv 12.1949). (80) Kalichevsky, V. A., Petroleum Processing, 4 , 1468 (1949). (81) Kantelius, K. E.H., Swed. Patent 126,731(Nov. 22,1949). (82) Kassing, B. L., Paper Ind. and Paper World, 32,430-3 (1950); Paper M i l l News, 73,No. 25,9-10, 18 (1950);Paper Trade J.,130, NO.24,874 (1950). (83) Keefer, C. E.,Sewage Works J.,21,554-76 (1949). (84) Kipp, E. M., Lubrication Eng., 4,122-4 (1948). (85) Kleinert, T., and Moessmer, V., Oesterr. Chem.-Ztg, 51, 29-32 (1950). (86) Klyachko, V.A., Stal., 8,818-22 (1948). (87) Korzhinskii, D. S.,Bull. m a d . sci. U.R.S.S., S b . gdool., 1947,No. 2,35-48. (88) Kraoklauer, A. C., Finish, 7,No. 4,2&6,73 (1950).
89
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1 .
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