INDUSTRIAL AND ENGINEERING CHEMISTRY
30
a means of separating components has continued, although progress in developing fundamental design data remains slow. Thc pattern for the future development of this operation has been reasonably well laid out. LITERATURE CITED
(1) Anon., Chem. Eng., 55, No.5,113 (1948). (2) Zbid., 55, No. 2,124 (1948). (3) Anon., Chem. Eng. News, 26, No. 25,1856 (1948). (4) Ibid., 26, No. 38,2771 (1948). (5) Anon., Chem. Inds., 63,590 (1948). (6) Anon., Taylor Technol., 1, No. 1,12 (1948). (7) Bauman, R. G., and Ruteler, J. E., Jr., Abstracts of Papers, 113th Meeting of AM. CHEM.SOC., Chicago, Ill., pp. 86-0, 87-0,1948. (8) Berg, C., and MoKinnis, A. C., IXD.ENG,CHEX., 40, 1309 ( .1948,). (9) Bewick, H.A., Currah, J. E., and Beamish, F. E., Anal. Chem., 20, 740 (1948). (10) Bilbe, C. W.,Chem. Eng., 55, No.8,99 (1948). (11) Bilbe, C. W., Oil Mill Gae.. 53, No. 1. 39 (1948). (12) Booth, H.S., and Everson, H. E., IND.EXQ.CHEM.,40, 1491 (1948). (13) Brancker, A. V., J . SOC.Chem. Ind., 66,453 (1947). (14) Brown, T. F.,IND.ENG.CHEM.,40, 103 (1948). (15) Buell, C. K., and Weinaug, C. F., U. S. Patent 2,436,502 (Feh. 24,1948). (16) Bush, M. T., and Densen, P. M., Anal. Chem., 20, 121 (1948). (17) Carter, J. C., U. 5.Patent 2,441,258 (May 11, 1948). (18) Craig, b., et al., Anal. Chem., 20, 134 (1948). (19) Cummings, L. O.,and Vogel, H. A., U. S. Patent 2,444,730 (July 6,1948). (20) Dickey, S.W., Culif. Oil World, 41,No. 10.19 (1948). (21) Dockendorff, R. L.;U. S. Patent 2,438,001 (March 16,1948). (22) Fan, H.P., Morris, J. C., and Wakeham, H., IND. ENG.CHEM., 40, 195 (1948). (23) Faquot, C., and Najand, A., Bull. soc. chim. France, 1948, 483. (24) Fawcett, E. W.hl., Chemistry d Industry, No. 41, 527 (Oct. 9, (1948). and Breston, J. N., J . Znst. Petroleum, 33,687 (25) Gauger, A. W., (1947). (26) Gloyer, s. IND. ENG.CHEM., 40, 228 (1948). (27) Gollmar, H.A., U. S. Patent 2,445,825(July 27,1948). (28) Griswold, J., Klecka, M. E., and West, R. V., Jr., Chem. Eng. Progress, 44, 839 (1948). (29) Haasel, Angew. Chem., A60, 4 (1948). (30) Harris, W.D., et al., J. Am. OiE Chemists’ Sue., 24, 370 (1947). (31) Hildebrand, J. H., Abstracts of Papers, 114th Meeting of AM. CHEWSOC., p. 15-0,1948. (32) Hooker, T., Chem. Eng. Progress, 44, 833 (1948). (33) Hougen, 0.A., IND. ENQ.CHEM.,40, 1561 (1948). (34) Igarashi, S.,J . SOC.Chem. Znd. J a p a n , 49, 67,135 (1946). (35) Johnson, H.G., and Piret, E. L., IND.ENG.CHEX.,40, 743 (1948). (March 23,1948). (36) Keeling, W.O., U. 9. Patent 2,438,368 (37) Keim, G. F., Ross, J., and Percy, J. € II b i. d ., , 2,444,293(June 29,1948). (38) Kemp, b. C., Jr., Hamilton, G. B., and Gross, H. H., IND. CNG. CHEM.,40, 220 (1948). (39) Kenyon, R. L., Gloyer, S. W., and Georgian, C. C., Ibid., 40, 1162 (1948). (40) Kenyon, R. L., Kruse, X. I?., and Clark, F. P., Zbid., 40, 186 (1948).
w.,
ms
Vol. 41, No. 1
(41) Knox, W. T., et al., Zbid., 39,1573 (1947). (42) baddha, G.S.,and Smith, J. M., Ibid., 40, 494 (1948). (43) Lassettre, E. N., Abstracts of Papers, 114th Meeting of AM. CHEM.Soo., p. 17-0,September 1948. (44) Leonard, R. H., Peterson, W. H., and Johnson, M. T., IND. ENQ.CHEM.,40, 57 (1948). (45) Lerman, F., Kennedy, A. B., and Laskin, J., Zbid., 40, 1753 (1948). (46) Licht, W., Jr., and Deneler, C. G., Chem. Eng. Progress, 44, 627 (1948). (47) Lyons, E. J., Ibid., 44, 341 (1948). (48) Mack, D.E.,and Kroll, A. E., Ibid., 44, 189 (1948). (49) Macy, R., J . Znd. Hug. Tozicol., 30, 140 (1948). (50) Meissner, H.P., and Greenfield, 5. H., IND.ENG.CHEX., 40, 439 (1948). (51) Mondiee, Adrien, Compt. rend., 225, 673 (1948). (52) Mysels, K.G., Pomeroy, H. H., and Smith, G. H., Anal. Chem., 20, 878 (1948). (53)Nachtrieb, N.H., and Conway, J. G., Abstracts of Pagers, 113th Meeting of AM. CHEhf. Soc., p. 88-0,April 1948. ENQ. (54) Othmer, D. F., Josefowitz, S., and Schmutzler, A. E., IND. CHBM.,40, 883,886 (1948). (55)Painter, E. V.,Anal. Chem., 20, 377 (1948). (56) Parlin, R., and Eyring, H., Abstracts of Papers, 114th Meeting of AM. CHEM.SOC., p. 16-0,September 1948. (57) Pratt, H.R. C., Znd. Chemist, 23,658 (1947). (58) Redlich, O., and Kister, A. T., ISD. ENQ.CHEM.,40, 341 (1948). (59)Ibid., 40, 345 (1948). (60)Redlich, O.,and Kister, A. T., J . Chem. Phys., 15, 849 (1948). (61) Rothschild, B. F., Templeton, C. C., and Hall, N. F., J . Phys. & Colloid Chem., 52, 1006 (1948). (62) Ruth, B.F.,Chem. Eng. Progress, 44, 71 (1948). (63) Scatchard, G., Abstracts of Papers, 114th Meeting of AM. CHEM. SOC., p. 15-0, September 1948. (64) Scheibel, E.G., Chem. Eng. Progress, 44, 681 (1948). (65)Ibid., 44, 771 (1948). (66) Serner, H. E., Chem. Eng., 55, No.8,118 (1948). (67) Shipley, G. H., and Wilson, G. W., Jr., U. S. Patent 2,436,494 (Feb. 24,1948). (68) Skolnik, H., IND.ENG.CHEM.,40, 442 (1948). (69) Simon, M.J., and Rau, M . A. C., Ibid., 40, 93 (1948). (70) Smith, E . L., and Page, J. E., J . SOC.C h m . Ind., 67,48 (1948). (71) Smith, W.V., J . Am. Chem. Soc., 70,2177 (1948). (72) Smoley, E. R., Petroleum Processing (August 1948). (73) Standard Oil Development Co., Brit. Patent 590,613(July 23, 1947), (74) Stingley, D. V., Znst. Spokesman (Natl. Lubricating Grease Inst.), 11, No. 10, 6 (1948). (75) Such, J. E., and Tomlinson, R. H., J . SOC.Chem. Znd., 67, 110 (1948). (76) Tiller, F. M., Chem. Eng. Progress, 44, 299 (1948). (77) Troyan, J. E., Rubber Age, 63,585 (1948). (78) Turehaus, A. C., and Ehlers, N. J., Chem. Inds., 63,230 (1948). (79) Vasseux, A., Inds. agr. et aliment. ( P a r i s ) ,65,21 (1948). (80) Visvanathan, T.R.. and Nandi, S. K., J. Sci. I n d . Research ( I n d i a ) , 7, No. 1, B, 1 (1948). (81) Weiemann, C., et al., J. SOC.Chem. Znd., 67,203 (1948). and Kwauk, M., Chem. Eng. Progress, 44, 201 (82) Wilhelm, R. H., (1948). (83) Zhuravlev, E. F.,and Bychkova, M.N., J . Gen. Chem. ( U . 8 . S.R.), 17, 1577 (1947). RECEIVED November 24, 1948.
T SHELBY A. MILLER
UNIVERSITY OF KANSAS, LAWRENCE, KANS.
F
ILTRATION continues to be the subject of a number of publications, many of them trivial, superficial, and repetitious, but some significant and contributory. The intent of this paper is to summarize those which have appeared in the year prior to October 1948,and are believed to be of importance or interest to the chemical process field; earlier publications of
value which have been delayed in reaching American readers or which have been omitted unintentionally from previous reviews of this series have been included. As in the past, the review is limited to noncentrifugal solid-liquid filtrations. A new approach to filtration theory has been made by Brownell and Katz (21). These authors first considered t h e flow of a
January 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
homogeneous fluid through a porous bed of spheroidal particles and succeeded in correlating the data of a number of investigators by means of a modified Reynolds number and a modified Fanning group. These quantities employed average particle diameter and bed thickness as the length terms and included the porosity of the bed and the sphericity and roughness of the particles. The authors then ingeniously modified their development to render i t applicable t o the flow of a two-phase heterogeneous fluid through a porous bed; they dealt with each phase as a homogeneous fluid whose behavior is affected by the other phase. They finally used their theory to develop equations for the filtration and dewatering periods of a vacuum filtration cycle, substantiating their derivation by showing close agreement between computed and observed simultaneous flow of air and glycerol through a bed of uniform lead shot. The advantage of the fluid-flow concept of cake deposition over the concept of specific resistance developed successfully by Ruth and others is doubtful, but Brownell and Katz have contributed significantly in their presentation of a method of computing combined gas-filtrate flow through a cake, provided their method is accurately applicable t o actual filter cakes. The idealized data employed in their initial correlation do not encourage confident extrapolation of their method to rough solids of a wide size range and complicated agglomeration (such as characterize chemical precipitates), and the difficulty of measuring average particle diameter, sphericity, and roughness limits the immediate practicality of their development. It is t o be hoped t h a t data soon will be collected and published t o support this commendable theory and convert i t into a working tool. Rosinski (60) reviewed the derivation of the usual equations for constant pressure filtration and applied them to the filtration of sugar-sirup mud. Although he placed what appears to be too much emphasis on the effects of scouring and cloth plugging and too little on cake compressibility, he nonetheless drew interesting conclusions about the optimum method of operating a battery of constant pressure filters to and from which a.filter must be added or withdrawn from time to time in the normal cycle of emptying and cleaning. I n essence, he recommended a method of automatically restraining the rate of filtration through a newly dressed at&until a cake had accumulated, with maintenance of a substantially constant rate of feed to the entire battery. Buchanan ($2) attempted t o derive equations which would permit the calculation of air leakage a t the couch and press suction rolls of a newsprint machine. It is believed t h a t his equations, substantiated by a single test, should be used with caution. EQUIPMENT
Several descriptive reviews (7, 11, 16,48) listing new filtration equipment have appeared; one of these (48) gave occasional performance data for specific applications of the filters discussed. I n general, the new equipment mentioned comprises slight modification of existing designs or represents merely a new item added to the line offered by a given manufacturer. Komline (49) improved the cord arrangement of a TiteflexWright vacuum filter t o permit easier, less expensive thickening of sewage sludge than was said to be possible with a cloth filter medium. A cake containing 72% water was produced. An equipment vendor announced (10) a new semiworks model of a string-discharge vacuum filter available on either a rental or a purchase basis. Ostenfeld (65) reported the development of a pressure-leaf precoat filter for sugar clarification. This filter is similar to a Sweetland press, but differs in its rectangular crosi section and in the fact t h a t it has a panel opening rather than a completely split shell. It may be operated at a pressure of 70 pounds per square inch. An in-line pressure filter now available (8) employs MicroMetallic stainless steel filtering elements which are replaceable to allow substitution of material of alternate porosities. Water filters were the subject of two patents ($6,97).
39
A number of publications have emphasized the corrosionresistance aspect of filter construction. Friend (54)described an alloy appropriate for filter presses used in soap production and for vacuum filter drums handling hot salt solutions. Inglesent and his co-workers (43, 44) pointed out the danger of corrosion of metals normally inert but made susceptible to attack because of galvanic action with an adjacent dissimilar metal. These investigators showed possible corrosion effects of this sort in sugar filters and outlined a test procedure whereby the resistance of various metals may be determined. A relatively small corrosion rate, they warned, can be destructive if the corroding item is a fine wire cloth, such as might be used for a filter medium. Two small filters designed expressly to process corrosive plating solutions have been reported ( I d , 68). A magnetic oil filter capable of removing ferrous particles as small as 0.00004 inch from 1500 gallons per hour of lubricating oil was announced (6) for installation on British Diesel-electric locomotives. A patent (88) has issued for a submerged belttype magnetic separator. Bliss has reproduced his welcome cost data on filters, first reported last year, in the new edition of a text book by Tyler (68), where they will be of particular value to students and practitioners of chemical engineering design. METHODS AND APPLICATIONS A number of specific industrial filtration applications have been described, although an unfortunately small amount of quantitative performance data accompanied the discussions. Lee (6.2)gave a general picture of molten sulfur filtration and reported throughput capacities for several of the filters used. Talbot (66) stated that a vacuum drum filter will produce (as cake containing 12 to 14% moisture) 100 dry pounds of a mineral concentrate per hour per square foot of filter area. The filtration of beer wort and the clarification of beer have been considered by several authors (58, 60, 66), one of whom (5U) has given approximate capacity figures for typical fillers. Weitnauer (70) recounted the factors involved generally in the filtration of beverage juices. The filtration of fermentable liquids is further complicated by the necessity of sterile conditions (50), a problem which is even more acute in the clarification of sterile medical products. For these latter materials, Edgington (33) recommended filter candles or fiber pads, rather than sand filters. H e cautioned against vacuum filtration, during which unsterile air may be drawn into the system. A Dutch patent (3.9)claimed that better washing and drying of a filter cake will result from building the cake of a number of thin superposed layers by periodically distributing the prefilt over a horizontal filtering surface. The sewage-sludge field has continued to contribute relatively more quantitative data than do chemical process plants. Among those who have reported filtration rates, equipment aize, and sludge characteristics are Kennedy (46), Nance (&), and Vick (69). Schroepfer (63)reported the cost of sludge filtration (exclusive of labor) for two different plants. Genter (35) has investigated in detail the exact coagulant requirements to produce sludge of the optimum consistency and has commented on the economies to be achieved by effecting a relatively drier filter cake. The value of careful research and development preliminary to plant design has been strikingly illustrated by Chicago's new South Side water plant (13). The gravity sand filters of this plant, which operate at unprecedented high rates, have been described (16,30). New high rate filters also have been installed recently at Geneva, Swifzbrland (23, 71). Dutton (31) remarked that i t is feasible to overload sand filters above their designed limit, but pointed out the precautions t h a t must be observed. Adams ( 1 ) discussed the operation of sand filters in the preparation of water for paper mills, where high rates can be used more safely than for potable water.
40
INDUSTRIAL A N D ENGINEERING CHEMISTRY
The importance of keeping filter sand clean was discussed by Haywood (39), who recommended a backwashing procedure, and by Matheson (53), who found that chlorine will remove nitrifying bacteria. Key (47) altered the design of wash-removal troughs to provide more effective backwashing without loss of sand. A recent War Department manual (16) corrected and evtended an earlier one (14); the two comprise exhaustive instructions on the installation and operation of small water filtration units. FILTER M E D I A
The new synthetic vinyl fiber with a higher temperature threshold than Vinyon, predicted recently by the patent literature, is now being manufactured. Known as Vinyon N, i t has been described comprehensively (61). Cady (24) has reported also that nylon can be felted in a wool or cotton mixture and shows promise as a filter medium. Alibert (8)claimed an advantage of continuous-filament fabrics as filter media. Ghelardi (36) commented on the tendency of synthetic fabrics t o ravel and suggested the use of heated cutting tools which fuse the newly cut edges. Leathart (51) recommended impregnating the gasketing areas of filter cloths with a nitrocellulose solution t o prevent vapor and liquid leakage from a filter press. Efforts to improve packs of bulk fibrous filter media used in clarifications have resulted in three patents (3, 2'9, 42'); one of these described a sandwich-pack composite suitable for use in a filter press. Porous metal (9) and sintered glass (6) filtering elements have been described briefly, and porous ceramic plates were reported (18) as possible substitutes for filter cloths in a plate-and-frame press. Winkelmann (72) described the use of sand as a filtering medium for lubricating oil. A laboratory supply house has published (4)a convenient table summarizing the properties of the common brands of filter paper. FILTER A I D S
Except for the suggestion by Bechtner (1'7) that his patented light-weight bentonite, produced by sublimation-drying of a frozen hydrosol, may be useful in filtrations, no papers have reported the use of new materials as filter aids. The few publications on the subject have been confined to diatomaceous earth. Thompson (67') described the use of diatomaceous earth for water filtration by American field troops during the war, and reported the subsequent peacetime use of similar precoat filters to condition water for swimming pools. He described typical filters and specified precoat loadings. Hoek (40) found that kieselguhr coated with an adsorptive gel permitted the filtration of unpretreated water that otherwise would quickly clog a ceramic filter, H e recommended admixture of additional filter aid to the water as it is being filtered. The belated report of a Czechoslovakian paper by Bretschneider (20) indicated that a mixture containing 2570 kieselguhr and 75y0activated charcoal speeded the filtration of sugar sirup with no sacrifice of decolorizing action. For undiscovered reasons, a 5OY0 mixture of carbon and kieselguhr, satisfactory in the laboratory, caused the filter cake to clog too quickly in the plant. Robertson (59) announced that Scottish deposits of diatomaceous earth are again being worked. He made no statement about the quality of the material mined. Crespin (37) described a n investigation of Australian diatomaceous earth as a potential filter aid, and concluded that the deposits are of marginal quality for this purpose but might be used locally. 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
Several novel pieces of laboratory filtration apparatus have been the subjects of short papers. Sutcliffe and Armitage (65) devised a vacuum filtration unit comprising a small filter candle i n an evacuated chamber. Isakov (45)described the use of a
Vol. 41, No. 1
micrometer plunger by which a carefully controlled vacuum can be applied to a, filter paper in an ordinary 60' funnel. Two pressure filters for the chemistry laboratory have been reported; one (68) of these permits operation at pressures up to 2 atmospheres. The other (41) consists of a porcelain disk in a thistle tube inverted in a flask; the vapor pressure of the liquid to be filtered is elevated by raising the temperature and forces the material through the disk and a filter paper placed against it. Bowden (19) devised a seamless cylinder of filter paper which conveniently fits a cylindrical funnel; since the diameter of the cylinder is only 5 mm., it is useful for the filtration of small quantities. Stene (64) found that a granular-bed filter of Aloxite of the proper size gave satisfaction with materials that would clog paper. Quigley (67) reported the filtration and ultrafiltration procedure which will fractionatc successfully the globulin and albumin in serum. LITERATURE CITED
Adams, R. R., Paper Trade J.,125, No. 24,43-7 (1947). Alihert, J., Chimie & industrie, 58, 341-5 (1947). Alsop, S., U. 5.Patent 2,435,115 (Jan. 27, 1948). Anon., Cenco News Chats, No. 61, 24 (1948). Anon., Chem. Age (London),59, 182 (1948). Ibid., p. 256-7. Anon., Chem. Eng., 55, No. 5, 121-2 (1948) Anon., Chem. Inds., 62, 270 (1948). Ibid., p. 272. Ibid., p. 620. Ibid., 63, PP. 403, 409-10. Ibid., p. 480. Anon., Eng. News-Record, 139,44-8 (1947). Anon., War Dept. tech. manual TM5-295, War Dept., Washington 25, D. C. (1945). Ibid., tech, manual TM5-295, C1 (1947). Baylis, J. R., IND. ENG.CHEM.,40, 1379-84 (1948). Bechtner, P., C. S. Patent 2,433,193 (Dec. 23,1947). Berkman, A. S., Stekol' naya i Keram. Prom., 1945, No. 3, pp. 1719. Bowden, S. T., Analyst, 72, 542 (1947). Bretschneider, R., Listy Cukrovar., 59,59-64 (1940). Brownell, L. E., and Kats, D. L., Chem. Eng. Progress, 43, 53748, 601-12,703-12 (1947). Buchanan, E. T., P u l p & Paper Mag. Can., 49, No. 3, 169-77 (1948). Buffle, J. P., Schweiz. Ver. Gas- u. Wasserfach., Monats-Bull., 26, 273-85,298-307 (1946). Cady, E. L., Materials & Methods, 26, No. 3,80-4 (1947). Camp, T. R., U.S. Patent reissue 23,009 (June 29,1948). Coleman, A. I., Chem. A g e . (London), 58,45-7 (1948) Crespin, I., Australia, BUT. Mineral Resources, Geol. Geophys. Bull., No. 7 (1947). Crockett, R. E., and Haselton, P. S., U. S. Patent 2,437,681 (Mar. 16, 1948). Davis, H. L., and Hervey, L. R. B., Ibid., 2,437,082 (Mar. 2, 1948). DeBerard, W. W., and Baylis, J. R., Water Works Eng., 100, 9002, 929 (1947). Dutton, L. F., J . New Engl. Water Works Assoc., 62, 95-8 (1948). Dwars, G., Dutch Patent 60,465 (Jan. 15, 1948). Edgington, B., Ind. Chemist, 24, 72-5 (1948). Friend, W. Z., Chem. Eng. Progress, 44, 501-10 (1948). Genter, A. L., Trans. Am. SOC.Civil Engrs., 111, 635-78 (1946); Water and S w a g e , 85, No. 2, 19-22,40,42-7 (1947). Ghelardi, R. A., Chem. Eng., 54, No. 11, 146 (1947). Grandin, J. R., and Mechlin, E. F., U. S. Patent 2,435,627 (Feh. 10, 1948). Harrison, E. W.?Am. Brewer, 80,No. 6,21-3, 62-4 (1947). Haywood, R. W., Jr., . I . Am. Water Works Assoc., 40, 410-14 (1948). Hoek, H., Gas- u. Wasserfach., 87, 145-8 (1944). Human, J. P. E,, and Mills, J. A., Chemistry & Industry, 1948, DD. 243-5. Huse, H. W., Faust, C. R., and Leininger, T. L., U. S. Patent 2,416,524 (Feb. 25, 1947). Inglesent, H., Manackerman, M., and Storrow, J. A., Ind. Chemist, 24, 76-84 (1948). Inglesent, H., and Storrow, J. A., Ibid., 23, 291-7.373-9.827-34 (1947). Isakov, P. M., J . #en. Chem. (U.S.S.R.), 18, 151-3 (1948).
January 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
Kennedy, C. C., Sewage Works J., 19,963-78 (1947). Key, T. D., J . Inst. CiviE Engrs. (London),29,323-34 (1948). King, W. W., Chem. Eng. Progress, 44, 717-20 (1948). Komline, T. R., Sewage Works J., 19, 806-10 (1947); U. S. Patent 2,426,886 (Sept. 2, 1947). (50) Laufer, S., FoodInds., 20, 208-11, 326,328,378-81 (1948). (51) Leathart, H. C., Chem. Eng., 54, No. 12, 139-40 (1947). (52) Lee, J. A., Ibid., 55, No. 4, 119-21 (1948). (53) Matheson, D. H., Water and Sewage, 85, No. 5, 85, 98, 100
(46) (47) (48) (49)
(1947). (54) (55) (56) (57) (58) (59) (60)
Nance, E. L., Sewage Works Eng., 19,355-7 (1948). Ostenfeld, H. B., Sugar, 43, No. 7,24-5 (1948). Pickard, J. A., Food, 16, 313-14 (1947). Quigley, J. J., J.Biol. Chem., 172, 713-16 (1948). Rayburn, V. A., U. 9. Patent 2,440,487 (April 27, 1948). Robertson, R. H. S., Chern. Age (London),59, 347-50 (1948), Rosinski, L., Chirnie & industrie, 59, 17-21, 131-43 (1948).
41
(81) Rugeley, E. W., Feild, T. A., Jr., and Fremon, G. H., IND.ENQ. CHEM.,40, 1724-31 (1948). (62) Scheidt, W., Pharmazie, 2, 15-17 (1947). (63) Schroepfer, G. J., Sewage Works J.,19,559-79 (1947). (64) Stene, S., Anal. Chem., 19,937-8 (1947). (65) Sutcliffe, A., and Armitage, E., Pharm. J.,159,393 (1947). (66) Talbot, H, A,, Deco Trefoil, 12, No. 2, 5-12 (1948). (67) Thompson, ’R.E., Water and Sewage, 85, No. 9, 31, 57-8, 60 (1947). (68) Tyler, C., “Chemical Engineering Economics,” 3rd ed., pp. 97-9, New York, McGraw-Hill Book Co., 1948. (69) Vick, E. H., Surveyor, 105, 883-6 (1946). (70) Weitnauer, G., Schwek-Brau. Rundschau, 54, 19-27, 41 3 (1947). (71) Werstadt, K., P a l h a a voda, 27, 122-5 (1947). (72) Winkelmann, We-rkstatt u. Retrieb, 79, 196 (1946). RECEIVED
October 25, 1948.
FLOTATION B!J. BRUCE CLEMMER, BUREAU
OF
UNITEDSTATES
MINES, TUCSON, ARE.
Y WAY of introduction, I should like to quote in part from a brief but explanatory editorial on flotation appearing in the March 1948 issue of Canadian Mining Journal: Any review of the progress that this particular branch of mineral dressing has made during the past quarter-century still brings a feeling of astonishment at the tremendous impact effected on the economic pattern of the mineral industry, in Canada no less than in other parts of the world. O m is on safe ground in averring that no other single metallurgical disc0ver.y of the past century has made available to the economic uses of man a greater quantity or variety of metals and diversified mineral products. Apart from quantitative considerations, the concentration and separation of minerals by flotation has had a profound, though indirect effect on the geographic distribution of ore deposit,s that could be exploited economically so that their metal or mincral content could be placed in the hands of man for his uses both peaceful and nefarious. The Aotation process has engaged the time and attention of a great many very able men in the establishing of the underlying principles involved and their application to practice, and new developments are constantly being made. The literature of the past year reveals that progress was made in applying the process t o a n increased variety of ores and nonmetallics and in explaining certain flotation reactions. Some of the more significant articles and patents will be detailed in this review, with only brief mention of others. This does not imply, however, that all are not important; together they serve as a basis for the more advanced studies and applications of the future. F U N D A M E N T A L AND THEORETICAL ASPECTS
The controversial subject of collector attachment t o mineral surfaces was discussed by Cook (14). H e contends that the present chemical and adsorption theories fail to explain the true mechanism of collection. He ascribes formation of collector coatings to adsorption of neutral heteropolar molecules. According t o this theory, for example, the flotation of galena by xanthates results from adsorption of neutral xanthic acid molecules rather than of xanthate anions. Similarly, free acid, free base, and neutral molecules are the effective entity for collection by long-chain paraffin acids, soaps, and salts. Although the theory aids explanation of several anomalies, many will question its validity. The application of radioactive tracers in flotation is being investigated in a n attempt to quantify the mechanisms of collection,
activation, depression, and frothing. Gaudin and co-workers (IS)described the equipment and procedure in use a t Massachusetts Institute of Technology, and several photographs of the apparatus were given in ( 1 ) . The study, sponsored by the Chemical Division of Armour & Company, Chicago, Ill., thus far has been confined to development of the technique for evaluating CI4-tagged n-dodecyl amine and lauric acid. Although more elaborate equipment is required, internal counting gave greater accuracy than window counters owing to relatively low energy (0.154 m.e.v.) and penetrating power of the emitted beta rays. The research on tagged reagents should go far toward explaining the mechanisms of flotation on a scientific basis. Spedden and Hannan (49)studied the contact and attachment of xanthate-coated galena particles on coursing free air bubbles A novel method was employed that embraced blowing air through a capillary tube into a glass flotation cell mounted on the stage of a microscope with a horizontal axis. The xanthate-conditioned particles were so introduced that the falling particles would meet the column of upward-rising bubbles in the field of view under 1SX magnification. A high-speed camera recorded the events at 3000 frames per second. They observed that a large proportion of particles making contact became attached t o the bubble surfaces; flow of fluid around the bubble surface influenced h e particles more bhan coarser sizes, but the flow did not prevent contact; the bubbles released from the submerged orifice were not spherical but exhibited an oscillating motion (changing shape) having a frequency of the order of 1000 per second. Several of the photographs given in the articles were subsequently reproduced ( 2 ) . REAGENTS
Several new reagents and novel reagent combinations for the flotation of sulfides and nonsulfides were reported. Bishop (6) patented the use of soluble salts of cymene sulfonic acid as frothing agents in the flotation of sulfides. Gibbs (24) used or-mercaptobutyric acid as the depressant in selective flotation of sulfides by conventional frothing and collecting agents. Moyer ($7) showed that sphalerite could be floated from chalcopyrite by using controlled quantities of lime and copper sulfate in conjunction with a dithiophosphate collector. Subsequent addition of lime and dithiophosphate permitted activation and flotation of the initially depressed chalcopyrite.
