Crystallization an
l X / E q Unit Operations Review
by HERBERT M. SCHOEN Radiation Applications, Znc., New York, N . Y .
An‘ impressive list of publications treated such topics as crystal growth, crystal habit and adsorption of consolutes, crystallization in sugar industry, and adductive crystalIization. Valuable contributions were made in: 0 0
0 0
IT
Growth of large single crystals Heavy and ordinary water separation by zone melting Industrial use of seeding Solid state nucleation theory
IS difficult to discern any trends in the crystallization literature of the past year. T h e newer aspects of the subject, such as zone-melting and single crystal growth from the melt and from solution, continue to dominate the literature; classical multicrystal growth from solution still receives little attention. There is, for example, no comprehensive treatment of the batch process in spite of its wide commercial application. T h e effects of controlled seeding and cooling upon product size distribution of a batch process have only been touched upon in the literature. Zone-melting, once limited to a very few materials such as silicon and germanium, is rapidly finding wider application in the separation and purification of organic and inorganic compounds. The effects produced by ultrasonic vibrations, electric fields, and ionizing radiation may have some interesting applications in the future. T o continue to emphasize areas of interest to chemical engineers and hold the review to a reasonable size, the subjects of spiral growth, whiskers, and crystallization equilibria have, for the most part, not been treated in this review,
Reviews and Books Once again a large number of review articles and books appeared in the literature. A comprehensive bibliography has 545 references pertaining to crystal growth ( I A ) . T h e proceedings of the International Conference on Crystal Growth, held at Cooperstown, N. Y., appeared in book form ( 5 A ) . A second edition of Saratovkin’s book (73A) on dendritic crystallization appeared in English translation. A number of stereoscopic photographs of dendrites are included. This treatment is nonmathematical. Whiskers were discussed by Hoffman ( 8 A ) . A summary of crystal habit and adsorption of cosolutes ( 3 A ) includes many references to publications subsequent to Buckley’s 1951 review. A reveiw ( 2 4 of the mechanism of diffusion in the solid state contains 192 references. General theories of crystallization, emphasizing nucleation and growth, were discussed ( 7 4 . T h e supercooling and nucleation of water were summarized (72A) An excellent volume discussed crystallization in the sugar industry ( 9 A ) . Over 100 references are included in a
survey of the present status of recrystallization research ( 4 A ) . Equilibrium and growth forms of crystals were discussed ( I O A ) , particularly supersaturation, nucleation, crystal growth from the melt, solution, and vapor phase. Experimental methods of studying the growth of individual faces were also treated. A most valuable addition to the literature on crystallization is a recent book (77A) on the preparation of single crystals. Although the book is nonmathematical in approach, it treats the many methods of growing single crystals quite thoroughly. A thorough treatment of adductive crystallization ( 6 A ) is of particular value to those interested in hydrocarbon separations.
Nucleation and Growth O n the assumption of a spherical nucleating particle, the effects of particle size and surface properties on nucleating efficiency were investigated (74B). In the condensation, freezing, and sublimation of water, nucleus size effect was found to be important in the 100- to 1000-A. range. Formulas for calculating the size of crystal nuclei, the probability of crystal formation and the shape of VOL. 52, NO. 2
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crystals formed in metallic systems were developed (75B). T h e classical theory of nucleation does not apply in a wide variety of solid-state transformations, according to Cohen (77B). I n solidstate transformations measurements do not depend on the birth of transformation centers but rather on the growth to a visible size of something already present. Nucleation rate in supercooled liquids was analyzed thermodynamically ( 79B). An empirical correlation was found (9B) between the time required for first appearance of nuclei and supersaturation. The compounds studied were potassium and ammonium chlorides, bromides, and iodides. I n studying the precipitation of hydrated aluminum oxide from sodium aluminate solutions, precipitation curves were found to be autocatalytic in nature (4OB). T h e mathematical techniques of Becker and Doring were applied (27B) to a cubic crystal, and an expression characteristic of a two dimensional nucleus was obtained. T h e parallelism of epitaxis and nucleation of the host material was discussed (24B). T h e crystallization of ammonium chloride was found to be influenced by a n electric field (34B). This was due to nucleation by charged dust particles entering the solution. Ultrasonic vibrations were found (4B) to have a great effect on the diffusion layer during dissolution. Sonic waves had no special effect on the rate of sugar crystal growth, but did enhance nucleation (39B). Ionizing radiation was used (5B) to grow and join crystals T h e interfacial reaction was found to be rate-controlling in the growth of ionic (728). An crystals from solution adsorbed surface layer on the growing crystals is proposed as the first stage in crystal growth from solution. T h e general mechanisms of crystal growth were also considered (6B). The atom-layer growth through surface nucleation occurs only for growth on material of the same composition. Growth on a material of different composition can occur with surface nucleation. Mechanisms were proposed for the growth of quartz crystals (26B, 42B). A general discussion of growth was given in terms of “physically possible” faces (3B). The combined mechanisms of nucleation and growth during precipitation reactions were discussed (78B). This approach should be of considerable interest to the chemical engineer. Crystallization was also treated (37B) as a two-stage process. Particle size of precipitated crystals was found to vary inversely as a low power of the cooling rate. The rate of solution of particles
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Table I. Materials Studied Sucrose CdS Cas04 CaC03 KCl Ag halides Terpin hydrate DDT Ice BzO s Rochelle salt Ge Sn Zn
Growth Ref.
( I B , 76B, 77B,38B) (27B, 28B) (29B, 43B) (33B) (35B) (32B) (37B) (256) (2OB) (70B) (2s) ( 47B) (7B, 73B) (36B)
in agitated liquids was studied (308). The findings on solution rate as a function of Reynolds numbers should be of value to workers interested in growth in agitated vessels. Vapor phase growth of benzophenone was treated (23B). A review and generalization of the Kossel growth theory appeared (8B). Crystal growth in porous media, such as ice in soil, was discussed (22B). Additional references to the crystal growth of specific materials are summarized in Table I.
Single Crystals The majority of the recent publications on single crystal growth relate to specific compounds rather than a generalized treatment of the subject. For the most part they pertain to the growth of crystals from the melt. Some of the recent contributions are discussed here; additional references are summarized in Table 11. A patent relating to the hydrothermal growth of quartz crystals from impure quartzite was granted (6C). I t required 26 days to grow crystals of approximately 50 grams, The growth of alakli halide single crystals from aqueous solutions was discussed (22C). Crystals weighing 40 to 50 grams were prepared in 10 to 15 days. When grown from solution some of the physical properties of the crystals were found to be superior to those of crystals grown by the Kryopoulos method. I n growing alkali halide crystals from the melt (79C),it was found that the cooling rate should not be more than about 2.25O C. per minute so as to avoid thermal stresses. A process for growing large single crystal boules of sapphire and corundum was patented (8C). Single crystal cylinders of variable length and contour were grown by a controlled reciprocating and rotating motion of the seed holder. A means of growing single crystal ferrites was also patented (23C). An apparatus for growing lead and tin single crystals
INDUSTRIAL AND ENGINEERING CHEMISTRY
from melts was described (7C). A crucible of spectroscopically pure graphite is used to contain the melt.
Zone Melting The literature pertaining to zone melting continue to increase a t a rapid rate. Some of the publications of particular interest to chemical engineers are cited here, while those pertaining to strictly analytical applications have been, for the most part, omitted. Techniques for floating zone refining of nickel, titanium, and vanadium and boat zone refining of aluminum and gold were described ( 7 2 0 ) . Magnesium was purified (730); all the major impurities except manganese form a eutectic system and are carried to the tail of the zone refined charge. Manganese migrates toward the head. Niobium was refined by the floating zone technique (20) in one pass using radio frequency current as the heat source. Tungsten was purified (30) using electron bombardment. The separation of hydrogen and deuterium in mixtures of ordinary and heavy water was investiagted ( 7 7 0 ) Continuous zone refining is the basis of a recent patent ( 8 0 ) . The charge is made to move across an open-top container by the moving heated zone which refines the material. Application of zone melting to both inorganic and organic compounds was discussed ( 7 0 0 ) . A number of radioactive tracers were used to check the results of purification. I t was shown ( 7 0 ) that zone-melting can also be applied to liquids by first solidifying them by freezing. Success was achieved using water and alcohol. Analytical solutions of Pfann’s integral equation for the ultimate impurity distribution along a bar were given ( 5 0 ) . The solutions hold for all values of the distribution coefficient and are not dependent on the bar length. The purification of aluminum and tin ( 4 0 ) and ice crystals ( 6 0 ) were also described. An apparatus for the purification of petroleum chemicals was described ( 7 0 ) . Zone melting with an immiscible liquid covering the material to be refined was discussed (9D).
Impurities and Additives After studying the distribution of an electrolyte impurity between a salt solution and crystals of another electrolyte, it was concluded ( 2 F ) that the distribution is regulated by ion exchange rather than the formation of a mixed phase. The rate of growth of ammonium sulfate crystals in the presence of various ions was investigated (73F). Control of the crystal shape by the addition of iron(II1)
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Unit Operations Review
COURTESY S W E N S O N EVAPORATOR CO
Ammonium sulfate crystallizer with a 12-foot diameter is designed for production o f 200 tons per d a y
ion is possible. Copper(I1) ion decreases this effect while ethylenediaminedinitraloacetic acid in the amount of 6 to 8 times that of the iron(II1) ion completely negates the effect. A model was proposed (72F) for solute diffusion in crystals with the diamond structure. Both the difference in size o f impurity ions and coulombic interaction between impurities and charged vacancies were found to be important. T h e effect of adsorption on crystal growth was the subject of two investigations (7F: 7763, Changes of crystal habit in the presence of additives were investigated (3F, 70F). In a British patent ( 8 F ) nitriloacetic acid is reported to increase the grain size of sodium chloride as \vel1 as increase its bulk density. In a study of the effect of additives on the crystallization of calcium sulfate ( 7 F ) , it was found, for example, that borax, citric acid, succinic acid, tartaric acid, gelatin, degraded keratin, and alginic acid retarded the rate of crystallization. Additives were chosen from the following classes of compounds : alkanols, dyes, amino acids, wetting agents, polybasic alcohols, simple organic compounds, and polymers. I n another study (4F) an emulsion was added to a solution containing a growing crystal. T h e form and nature of the occlusions depended upon the magnitude of the wetting of the crystal surface by the petroleum and the rate of growth. Solid suspended impurities ( 9 F ) were
found to be enveloped in the growing crystals more readily at high growth rates. T h e minimum rate of growth necessary for envelopment depended upon the nature of the suspended particle as well as the nature of the crystal growing from its melt. The incorporation of foreign ions into a crystal lattice was discussed ( 5 F ) . It was reported ( 6 F ) that the presence of univalent ions often had the effect of diminishing thr supercooling of water.
Table II.
Growth o f Single Crystals Ref.
Substance
Si Sic: Ge GeOz Barrioa LbI'iO,
Zr CdS ZnS HgSe
W ZnO A1 NH (H z P 0 4 Triglycine sulfate Heptahydrates of metal sulfates
( 76C, 27C) (78C)
(72C, 73C) ( 72C, 13C) ( 73C) i5C)
(3cj
( 7 7C) (2G
(26C)
( 2 G
Equipment and Apparatus
A large number of devices for growing crystals from the melt were described in the literature (mainly patents). An apparatus for fractional crystallization (77G) produced 99% (weight) of p-xylene from a 41y0 feed. T h e separation of xylene isomers in a continuous countercurrent crystallizer was reported (20G). Equipment for the purification of xylenes was described (78G, 22G). Small crystals were grown from the melt in a screw conveyor-type crystallizer (2G). The growth of napthalene and anthracene crystals u p to 3 feet in length was reported (8G). T h e furnace is designed to minimize convection currents and allow observation of the growing crystals. Several other crystal growth furnaces were described (70G, 72G, 79G, 27G). Industrial Practice Sodium sesquicarbonate, its properties and manufacture were the subject of a series (27H-23H). Some of the factors influencing the size of crystals and yields were cooling rate and the presence of other salts. Crystallization operations at Trona were reviewed ( 7 H ) . Processes were also described for crystallizing borax ( 8 H ) , calcium sulfate ( 7 8 H ) , and sodium sulfate from Searles Lake brine (2"). T a b k I11 lists some additional crystallization equipment. VOL. 52,
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Table 111.
Crystallization Equipment
Subject Crystal purification with cone shaped baffle Externally cooled vessel with scraper Vacuum crystallizer with gas bleed Continuous crystallization of calcium sulfate from sulfuric acid solutions Stair-shaped crystallizer Tubular crystallizer used in Soviet coke industry Rotating porous cylinder used as crystallizer Circulating crystallizer for growing piezoelectric materials Crystallizer for growing Rochelle salt Device for investigating microscopic growth of crystals Low temperature crystallizer for laboratory Growing cadmium sulfide crystals
The conditions for producing a cast alum of lustrous appearance were described by Peckham (20H). A continuous process for producing rhombic ammonium sulfate crystals (24H) involves the addition of tannin to the crystallizing solution. T w o patents (27H, 28H) pertain to the recovery of crystalline sulfuric acid from spent alkylation liquors. T h e impure acid is sprayed into an organic phase, and subsequently separated. A number of patents were issued relating to the separation and purification of xylenes. I n a two-stage operation (74H)99% pure xylene was obtained from a crude feed containing 17, 17.5, and 33.4’3&, respectively, of p-, 0-, and rn-xylene, as well as 27.5% ethylbenzene and 4.6y0 toluene. A continuous process for xylene separation was described (70H). Another patent ( 9 H ) describes the preparation of a partially solidified feed slurry for charging to the crystallization apparatus. Fractional crystallization processes for xylenes (77H, 30H) involve the use of a reciprocating piston to press the mother liquor from its slurry. High purities were obtained. A selective freezing process was patented (75H) for separation of gaseous mixtures. Seeding was found ( 3 H ) to reduce sludge volume in sulfuric acid waste disposal. T h e calcium sulfate was deposited on native gypsum seeds. Stirring intensity was reported (77H)to affect the purity of crystals. A means of preserving the surfaces of crystals against the development of cracks and imperfections was patented (76H). Processes for the growth of monosodium glutamate
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(25H),silicon ( I H ) ,trisodium phosphate (37H), ferroelectric crystals (79H), and small spherical crystals ( 2 6 H ) were reported. Two studies (5H, 6 H ) concern cooling rate in sugar crystallization. A multistage process ( 4 H ) is applicable to the concentration of fruit juices, beer, wine, and liquors. T h e adjustment of p H during crystallization (72H) produced a highly crystalline structure in materials which are normally amorphous. A process for obtaining sodium chloride of high purity was described (73H). Cooling rather than evaporation was recommended (29H) to avoid decomposition during the production of ammonium selenite. Acknowledgment T h e author wishes to acknowledge the efforts of C. S. Grove, Jr., who has coauthored these reviews for the past 12 years. I t is with regret that he does not appear as coauthor this year. Thanks are also due to Barbara Booth, Christine Schoen, Marcia Potter, and Maryann Tartaglia for assisting in the preparation of this review.
Bibliography Reviews and Books (1A) Bennett, F. G., U. S. Atomic Energy Comm. S.R.-2693 (1958). (2A) Birchenall, C. E., Metals Rev. 3, 235 (1956). (3A) Bliznakow, G., Fortschr. Mineral. 36, 149 (1959). (4A) Borchers, H., Jordan, H., Schwarzwalder, R., Metall 13, 12 (1959). (5A) Doremus, R. H., Roberts, B. W., Turnbull, D., eds., “Growth and Perfection of Crystals” (Proc. lntl. Conf. Crystal Growth, Cooperstown, N. Y., August 1958) Wiley, New York, 1958. (6A) Findlay, R. A., Weedman, J. A., “Separation and Purification by Crystallization,” in “Advances in Petroleum. Chemistry and Refining,” vol. I, p. 116, Interscience, New York, 1958. (7A) Grove, C. S., Jr., Schoen, H. M., Chim. ezng. (Rome) No. 4,2 (1957). (8A) Hoffman, G. -4., J . Metals 10, 591 (1958). (9A) Honig, P., “Principles of Sugar Technology. Vol. 11, Crystallization,” Van Nostrand, Princeton, N. J., 1958. (10A) Honigmann, B., Fortschr. physik. Chem. 4, p. 1-161 (1958). (11A) Lawson, W. D., Nielsen, S., “Preparation of Single Crystals,” Academic Press, New York, 1958. (12A) Mason, B. J., Advances in Physics 7, 221 (1958). (13A) Saratovkin, D. D., “Dendritic Crystallization,” 2nd ed., Consultant’s Bureau, Inc., New York, 1959. Nucleation and Growth (1B) Albon, N., Dunning, W. J., Acta Cryst. 12, 219 (1959). (2B) Alyavdin, N. V., Izvest. Vysshikh Ucheb. Zavednti, Fiz. No. 6, 44 (1958). (3B) Ansheles, 0. M., Uchenye Zapiski, Leningrad. Gosudarst. Univ. im. A . A. Zhdanoua No. 215, Ser. Geol. Nauk. No. 8,84 (1957).
INDUSTRIAL AND ENGINEERING CHEMISTRY
(4B) Bagdasarov, Kh. S., Kristallograjiya 3, 110 (1958). (5B) Baskin, M. L., Semerchan, A. A., Vestnik Akad. Nauk. S.S.S.R. 28, No. 1, 69 (1958). (6B) Bauer, E., Z. Krist. 110,372 (1958). (7B) Becker, J. H., J . Appl. Phys. 29, 1110 (1956). (8B) Bukovszky, F., Acta. Phys. Acad. Sci. Hung. 8,109 (1957). (9B) Chatterji, A. C., Singh, R. N., J.Phys. Chem. 62,1408 (1958). (10B) Clausen, W. F., MacKenzie, J. D., J . Am. Chem. Soc. 81,1007 (1959). (11B) Cohen, M., Trans. Met. SOC. AIME 212. 171 (19581. - - (12B) ’Doremus, R . H., J . Phys. Chem. 62, 1068 (1958). (13B) Ewald, A. W., Tufte, 0. N., J . Appl. Phys. 29,1007 (1958). (14B) Fletcher, N. H., J . Chem. Phys. 29, 572 (1958). (15B) Gardonyi, S., Kohhszati Lapok 92, 23 (1959). (1GB) ‘ Golovin, P. V., Gerasimenko, A. A., Abramova, M. A., Sakharnaya Prom. 32, No. 3, 10 (1958). (17B) Ibid., 33, No. 1, 28 (1959). (18B) Hahnert, H., Kleber, W., KolloidZ. 162, 36 (1959). (19B) Hoffman, J. D., J . Chem. Phys. 29, 1192 (1958). (20Bj Isono, K.,’ Nature 182, 1221 (1958). (21B) Kaishev, R., Acta Phys. Acad. Sei. Hum. 8.75 (1957). (22B) UKhaimov-Mal’kov,V. Ya., Kristallogra ya 3, 488 (1958). (23Bf Kitchener, J. A., Strickland-Constable, R. F., Proc. Roy. SOC.(London) A245, 93 (1958). (24B) Kleber, W., Weis, J., Z. Krist. 110, 30 (1958). (25B)‘Kulkarni, S. B., Kuber, M. V., Biswas, A. B., J . Sci. Ind. Research (India) 17B, 212 (1958). (26B) Laudise, R. A., J . Am. Chem. SOC. 81, 562 (1959). (27B) Medcalf, W. E., Fahrig, R. H., J . Electrochem. Sac. 105, 719 (1958). (28B) Miller, R. J., Univ. Microfilms (Ann Arbor. Mich.). L. C. Card No. Mic-58-2306; Dissertation Abstr. 19, 2368 (1959). (29B) Moriyama, T., Utsonomiya, T., Miyauchi, T., KBgyB Kagaku Zasshi 60, 238 119571. ~ ~,_ . . (30Bj Nagata, S., Adachi, M., Yama uchi, I., Mem. Fac. Eng. Kyoto Univ.20,72(f958). (31B) Packter, A., Z.physik. Chem. (Leiptig) 210, 197 (1959). (32B) Perry, E. J., J . Colloid Sci. 14, 27 (1959). (33B) Sakaguchi, M., Yogyo Kyokai Shi 66,165 (1958). (34B) Saratovkin, D. D., Kulikov, V. A., Izvest. Vysshikh. Ucheb. Zavendenir, Fir. No. 4, 140 (1958). (35B) Sears, G. W., J . Chem. Phys. 29, 979 (1958). (36B) Siems, R., Haasen, P., Z . Metallk. 49, 213 (1958). (37B) Sil’vestrova, I. M., Aleksandrov, K. S., Chumakov, A. A., Kristallografiya 3, 386 (1958). (38B) Van Hook, A., Ind. saccar. ital. NO. 11-12, 3 (1958). (39B) Van Hook, A., Radle, W. F., Bujaki, J. E., Casazza, J. J., J. Am. Soc. Sugar Beet Technologists 9, 590 (1957). (40B) Vrbaski, T., Ivekovic, H., Pavlovic, D., Can. J . Chem. 36, 1410 (1958). (41B) Zielasek, H., Z . Naturforsch. 13a, 1097 11958). (42B) Zimonyi, Gy., Acta Phys. Acad. Sci. Hung. 8,119 (1957). (43B) Zolotov, V. A., Kristallograjya 3, 237 (1958).
.
an Single Crystals (1C) Ascoli, -4.,Germagnoli, E., Energia nucleare(Mi1an) 5 , 591 (1958). (2C) Billig, E., Gasson, D. B., J . Sci. Znstr. 35; 360 (1958). (3C) Bogner, G., Mollwo, E., Phys. and Chem. Solids 6,136 (1958). (4C) Bradshaw, S. E., Mlavsky, A. I., U. S. Patent 2,851,342 (Sept. 9,1958). (5C) Brenner, S. S., Morelock, C. R., Zbid., 2,836,524 (May 27, 1958). (6C) Brown, C. S., Kell, R. C., Brit. Patent 797,203 (June 25, 1958). (7C) Dash, b’.C., J . Appl. Phys. 29, 736 (1958). (8C) Drost, W., Kleber, W., U. S. Patent 2,852,890 (Sept. 23, 1958). (9C) Fukuda, K., Okuda, A., Uchida,. Y .., 6yd Butsuri27, 535 (1958). . (1OC) Goorissen, J., Karstensen, F., Z . Metallk. 50, 46 (1959). (11C) Goux, C., Montuelle, J., Compt. rend. 246, 1691 (1958). (12C) Green, L. C., Reynolds, D. C., J . Chem. Phys. 29, 1375 (1958). (13C) Hamilton, D. R., Brit. J . Appl. Phys. 9 , 103 (1958). (14C) Hamilton, D. R., J . Electrochem. SOC.105, 735 (1958). (15C) Horn, F. H., Ibid., 105, 393 (1958). (16C) Khodakov, A. L., Sholokhovich, M. L., Zzvest. Akad. Nauk. S.S.S.R., Ser. Fir. 22, 1445 (1958). (17C) Kikuchi, M., Iizima, S., J . Phys. SOC.Japan 13, 319 (1958). (18C) Kobayashi, J., J . App . Phys. 29, 866 (1958). (19C) Kuchin, V. D., Izvest. Vysshikh Ucheb. Zavendenir, Fiz. No. 2, 117 (1958). (20C) Kunisaki, Y., *Vuture 183,105 (1959). (21C) Langeron, J. P., Lehr, P., Rev. mit. 5 5 , 901 (1958). (22C) Melik-Gaikazyan, I. Ya., Ermolaev, V. -4.,Zzvest. Uysshikh Ucheb. Zauedenii, Fir. No. 5 , 141 (1958). (23C) Remeika, J. P., U. S. Patent 2,848,310 ( h g . 19, 1958). (24C) Smakula, A,, Kalnajs, J., Phys. and Chem. Solids 6,46 (1958). (25C) Stepanov, I. V., Sinyukova, I. A., Chernevskaya, E. G., Optika i Spektroskopiya 4, 272 (1958). (26C) Tanaka, Y., Waku, S., o y 6 Butsuri 27, 561 (1958). (27C) Timofeeva, V. A., Pleteneva, I. A., Kristallografya 3,214 (1958). (28’2) Voronkov, A. A., Zbid., 3, 240 (1958). ( 2 k ) Yoda, H., Japan. Patent 7411(’57) (Sept. 11). \ - . - - / .
Zone Melting (1D) Ball, J. S., Helm, R. V., Ferrin, C. R., Petrol. Engr. 30, No. 13, C36 (1958). (2D) Buehler, H., Trans. Am. Znst. Mining, Met., Petrol. Engrs. 212, 694 (1958). (3D) Carlson, R. G., J . Electrochem. SOC. 106. 49 11959’1. (4D) Chen, N.‘K., Liu, M. C., Chin Shu Hsueh Pao 2, 163 (1957). (5D) Davies, L. W.,Phzl. M a g . [8] 3, 159 (1958). (6D) Decroly, J. C., Jaccard, C., Helv. Phys. Acta 30, 468 (1957). (7D) Izergin, A. P., Izvest. Vysshzkh Ucheb. Zauedntr, Fir. No. 5 , 115 (1958). (8D) Pfann, W. G., U. S. Patent 2,852,351 (Sept. 16, 1958). (9D) >bid., ‘2,875,’108 (Feb. 24, 1959). (10D) Sue, P., Nouaille, A , , Bull. SOC. chim. France 5,593 (1958). (11D) Thomas, C. O., Univ. Microfilms (AFn Arbor, Mich.), L. C. Card’No. Mic. 58-1327; Dissertation Abstr. 18, 1279 (1958).
(12D) Wernik, H., Dorsi, D., Brynes, J. J., J . Electrochem. SOC.106, 245 (1959). (13D) Yue, A. S., Clark, J. B., Trans. A m . Znst. Mining, Met., Petrol. Engrs. 212, 881 (1958). Caking and Its Prevention (1E) Abe, S., Seito Gijutsu Kenkyukaishi 6, 1 (1957). (2E) Ajinomoto Co., Brit. Patent 789,565 (Jan. 22, 1958). (3E) Ames, J., Pierpoint, K., Ibid., 803,192 (Oct. 22, 1958). (4E) Hoshikawa, M., Kajiwara, I., Kotake, T., Nagamune, S., Japan. Patent 7412(’57) (Sept. 11). (5E) Hoshikawa, M., Kotaki, T., Nagamune, S., Oguni, O., Japan. Pat. 2866(’58) (April 19). (6E) Iwase, M., Japan. Patent 6616(’57) (Aug. 24). (7E) N. V. Koninklijke Nederlandsche Zoutindustrie, Dutch Patent 84,368 (March 15, 1957). (8E) Societe Carbochimique S. A., Brit. Patent 800,483 (Aug. 27, 1958). (9E) Stoess, H . A , , Jr., Tappi 41, No. 4, 221A (1958). Impurities and Additives (1F) Bliznakov, G., 2. physik. Chem. (Leipzig) 209, 372 (1958). (2F) Chuiko, V. T., Zhur. Neorg. Khim. 2. 7764 \-.-.,. --- ’ (1057) -I
(3F) Comer, J. J., J . Colloid Sci. 14, 175 (1959). (4F) Kliya, M. O., Sokolova, I. G., Kristallografya 3,219 (1958). (5F) Kroger, F. A., Vink, H. J., Phys. andChem. Solids5, 208 (1958). (6F) Lafargue, C., Compt. rend. 246, 1894 11958’1. (7F) McCartney, E. R., Alexander, A. E., J . ColloidSci. 13,383 (1958). (8F) N. V. Koninklijke Nederlandsche Zoutindustrie, Brit. Patent 790,457 (Feb. 12. 1958). (3F).Pikunov, M. V., Metalloved. i Obrabotka Tsvetnykh. Metal. i Splauou, Sbornik Stater 1957, p. 55. (10F) Scnerb, I., Bloch, M. R., Bull. Research Council Israel 7A, 179 (1958). (11F) Sears, G. W., J . Chem. Phys. 29, 1045 (1958). (12F) Swalin, R. A . , J . AppZ. Phys. 29, 670 (1958). (13F) Yamada, T . , Kawasaki, T., Naruse, M., Sugiura, M., Nagoya K6gy6 Daigaku Gakuho IO, 176 (1958). Equipment a n d Apparatus (1G) Christensen, C., U. S. Patent 2,863,740 (Dec. 9, 1958). (2G) Erbe, F., Maikowski, M. A., Ibid., 2,863,739 (Dec. 9, 1958). (36) Furuichi, K.,. Japan. Patent 1466 (’58) (March 5). (4G) Iwata, Y.,Yamamoto, K., Japan. Patent 21(’58) (Jan. 10’1. (5G) Kaianne. P.: Suomen‘Kemirtrlehti 31B, (6G) Kozlovskii, M. I., Kristallograjya 3, 509 (19%). \----,.
(7G)- Lipscomb, R., Craig, A., Labrow, S., Dunn, J. F., U. S. Patent 2,857,745 (Oct. 22. ... _ _ , 1958’1 Lipsett, F. R., Reu. Sci. Instr. 29, ( 8 2 3l(1958). (9G) McCay, D. L., U. S. Patent 2,882,133 (April 14, 1959). (10G) Marshall, J. C., Wickham, R., J . Sci. Instr. 35, 121 (1958). (11G) Miller, R. J., Bachman, C. H., J . Appl. Phys. 29, 1277 (1958).
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Unit Operations Review
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