Tin and Its Alloys w
ROBERT J. NEKERVIS Tin Research Institute, Inc., Columbus I , Ohio From a supply standpoint, tin is considered to be scarce because maior fields are in the Far East and are considered vulnerable. Production of tin has increased since World War I1 and for the past 3 years has been in excess of consumption. This excess has been purchased by governments for stockpiling; most of it by the United States Government. United States stockpiles of tin are in considerably better shape than they were at the start of World War 11. Probably the outstanding technical development of the past year in tin is the development of a bright 65/35 tin-nickel electroplate which has applications and properties similar to chromium-on-nickel electroplates. Other noteworthy developments are improved soldering methods for aluminum and for wiped joints. There has also been a considerable number of new developments in tin plate manufacture and in canning technology.
T
HIS year, because of the current metal shortages, a brief
summary of the tin supply picture is as necessary as a Bummary of new developments. The free use of tin, of course, is again restricted in the United States. The supply picture is a relatively good one, however, as the follor?ing figures taken from the International Tin Study Group's statistical bulletin for May 1951, will attest:
1949 1950
World Production, Long Tom 168,100 171,000
World Consumption, Long Tons 116,600 161,400
World Stocks5 ( a t End of Period Shown), Long Tons 132 200 (December 1949) llf3,'OOO (November 1950)
figure a n estimated 120,000 long tons transferred t o the United States strategic stockpile.
Production has increased in spite of considerable Communistinspired banditry in the largest tin producing area, Malaya. The mad scramble to stockpile tin following the war in Korea has pretty well subsided fiince the IJ. S. Government halted, temporarily, the buying of tin for the strategic stockpile. This action, taken on March 6, 1951, was in accord with the wishes of the producers. The market for tin was free, and eager government buying coupled u ith the inevitable speculation which occurs in a free market, drove the price up so rapidly that producers were genuinely worried about the future of tin for estahlished uses. The present price of tin is about where it was when it was removed from the U. S. Department of Commerce restricted list in 1949. The prices of most other metals have risen drastically during this period. World supplies of tin are more than adequate for peacetime rates of use. Unsettled world conditions, which usher in strategic stockpiling programs, introduce imponderables which are difficult to assess. Detailed studies of the position and prospects of the tin industry have been made by the Tin Study Group (71-rs). TIN ALLOY PLATING
Probably the most significant development during the past year from the chemical engineering standpoint is the development of a bright tin-nickel electroplating process (104). Figure 1 shows an application for this alloy coating. Two outstanding features of the process are the ease with which a constant composition (65 Sn/35 Ni) can be obtained and the extreme tarnish resistance of the deposit. The composition is constant even over very wide variations of current density, temperature, and bath composition. The deposit is resistant to attack by cold mineral
acids: it is almost immune to attark by inhibited hydrochloric acid and ti) hot concentrated nitric acid. An Yray investigation of the structure of tin-nickel electrodeposits has been made (115). Probably equally important to the chemical engineer are properties of rr6ently developed e le c t r o p l a t e d alloy coatings such as tin-zinc and tin-cadmium. Attention has bern called to data which show that tinzinc alloys have corrosion protection properties close to cadmium (61, 128) The ease of solderability of tin-zinc is similar to cadmium Spot welding properties are superior t o cadmium and close to zinc (61). A 'method for plating a tin-cadmium alloy has been developed (118). The alloy deposit obtained, 75 Cd/25 Sn, has far better corrosion resistance on low alloy steel than eithcr cadmium or tin (118). A new plating bath for bronze has been developed (125). The Russians have also investigated the deposition of bronzes ( 4 2 ) . The bath they used is similar to the stannate-cyanide bath for plating speculum (45 Sn/55 Cu) TI hich was developed by the Tin Research Institute several years ago. Using this speculum bath containing various brightening agents, Cuthbertson (36) has shown that it is possible to have good throwing power with rcspect to thickness associated viith a poorer throwing power with respect to composition and vice versa. Two patents covering modifications of this bath have been issued (6, 85). Bennett has investigated the feasibility of using brighteners in this bath (12). The structure of tin-copper alloys hax heen the subject of two inveetigations (98, 114). A barrel plating method to achieve fine-grained adherent tinlead coatings has been described (119). Patents on a method for bright plating copper-tin-zinc alloys ( 7 4 )and a method for obtaining tin-nickel, tin-copper, and tin-lead coating through a combination of electroplating and diffusion ( 1 0 0 )have been issued. TIN ELECTROPLATING
Again, attention has been called to the Bullard-Dunn electrolytic descaling and tin-plating process (145). The unique feature of this process is the use of tin as an inhibitor in a descaling bath. Once the oxide is removed, further attack is prevented by a uniform deposit of tin. Stringent restrictions on tin have prevented the commercial development of thip process. Hydrogen embrittlenient in tin electroplating has been studied (147). This particular report showed that when plating conditions stray from recommended practice, hydrogen embrittlement will result. Unfortunately, recommended practice was not covered in the report. It will be covered later, however. Wire tinning (84, 85),electropolishing of tin ( l o g ) , and the use of electro-tin coating as a base for paint (125) have been discussed. A patent covering immersion tinning of ferrous articles has been issued (68). ELECTRO-TIN PLATE
Hoare has written a comprehensive review of developments to date in the manufacture of electro-tin plate (64). Improvements in chloride-fluoride (halogen) electrotinning baths (69, 117) and in stannous phenolsulfate (Ferrostan) electrotinning baths (SO) 2272
October 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
have been patented. Glock has been granted a patent on a novel method of achieving brighter electro-tin plate having better adherence in a sodium stannate electrotinning bath (66). The novel feature is a reversal of current during the &st part of the travel of the strip through the bath, obtaining, in effect, anodic cleaning during this portion of the plating cycle. A cathodicchromate treatment to improve the adherence of flow-brightened tin plate has also been patented (107).
2273
evaluation of lacquers have been given considerable attention (66, 99, 101, 133). The Tin Research Institute has published a manual on tin plate for the guidance of users (66). Factors to consider in the design of caps and production tools for lever-lid containers have been investigated (8%). SOLDERS
Can Solders and Soldering Methods. High lead solder (2 TIN PLATE MANUFACTURE
New methods of measuring tin coating thicknesses using an xray thickness gage have been developed (10, 28, 76). A commercial unit embodying this principle, the Norelco Geiger counter tin plate thickness gage, is in use at several plants. It provides a quick, nondestructive measurement and is admirably suited for quality control ($8). A patented rapid chemical method for measuring tin coating thickness, the Bendix method (11),has been made available to industry, license-free (27). George and Haab have patented a method for producing tin plate that is free from “earing” (uneven stretching) when it is drawn. The patent a1so includes a nondestructive test for measuring earing characteristics (54). Other developments in tin plate manufacture worth noting include a patent covering a combination pickling and hot-tinning unit (lis), an investigation on continuous annealing schedules ( 7 7 ) ,and on palm oil substitutes for hot tinning (76). TIN-PLATE CONTAINERS
Corrosion studies have yielded some practical information on the nature of tin plate corrosion in food packs. Vaurio, using prune packs, has shown that the distribution of tin over the inside of a can is relatively unimportant. Important factors are the amount of tin present for cathodic protection and the corrosion resistance of the steel base (138). Kohman has explained the perforation corrosion of tin-plate covers on glass containers and has suggested corrective measures (80). The corrosion resistance of lacquered iron has been compared with tin plate (81). In this connection, the public announcement of the American Can’s ‘‘tinless can” research project has provoked much interest (89, 90); results of the investigation are eagerly awaited. Reasons for lacquering tin plate, methods of application, and
Sn/98 P b ) currently being used commercially in the United States appears to be safe from the standpoint of lead pickup in canned food (39). A patent has been granted on an inductionheated can-soldering machine (26). Aluminum Solders and Soldering Methods. The deveiopment of aluminum-sheathed cables has focused attention on aluminum solders and soldering methods (143). The trick in soldering aluminum is to use a flux that will not only remove the oxide surface but also keep the surface reduced until tinning by the solder has taken place. Such a flux, developed some years ago, has again received attention (97, 148). Ultrasonic vibration provides another means of removing the aluminum oxide skin long enough for soldering t o take place. The designers of a supersonic solder,ing iron for factory use have shown that the process involved is one of cavitation erosion (103). Since aluminum is high in the electromotive series, suitable solder alloys are also a problem. A considerable amount of investigation has taken place in this field (31, 96,111). The effect of the solder on the aluminum alloy must also be considered. Some aluminum alloys are subject to embrittlement as a result of penetration by the solder. Methods of preventing such embrittlement have been studied (94). New Solder Alloy Developments. The Bell Telephone Laboratories have developed a unique method of overcoming porosity in wiped joints; a lower melting solder is rubbed over the wiped joint as soon as wiping is completed (19, 106, 116). Another important development is the achieving of fine-grained, drossfree, wiping solders (nominal composition 25 to 30 Sn/75 to 70 Pb) by adding 0.1% arsenic to the alloy (116). Practical results are improved handling characteristics and freedom from porosity in the finished joint. Still another development of the Bell LaboratorieR is soldering alloys, free from low boiling constituents, for use in vacuum tubes (111).
Figure 1. Tin-Nickel Alloy Plating on Commercial Items This illustration points up the promise of this new plating material as a protection for industrial equipment
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Indium-bearing solders having improved alkali resistance have been developed (69). A study of developments in tin-conserving solders shows that silver is the only readily available metal that can be substituted for tin on a metallurgically sound basis (26). Soldering Pastes and Fluxes. New formulas for soldering pastes for general soldering ( S 8 ) , for solderlng electronic parts (105), and for soldering plated aluminum (60) have been developed. A flux in the form of a thin grease has been developed for automobile body soldering (140). New noncorrosive, nonconductive fluxes (46, 87) have been developed. Recent Advances in Soldering Methods. Watkins has written a n excellent review of recent advances in solders and soldering (148). Investigations in important related fields by Watkins and hki colleagues are covered in the article. Work on the relationship between wetting and surface roughness (122)and work on the surface tension in solid-liquid systems (8) are discussed from the standpoint of soldering. A solder performance tester developed by Bailey and Watkins is also described (7). A new “gun” method of brazing and soldering has been designed for use with a conveyor system (3,20). HOT TINNING
There are numerous instancea in chemical engineering where the hot-tinning of cast iron is necessary Bearing shells are an example. Successful methods of hot-tinning cast iron are covered in American (as), British ( 6 3 ) , and German (93) publications. A resin for masking off parts of articles during hot tinning has hem patented ( 3 5 ) . TIN-CONTAINLNG MATERIALS
Tin Bronzes.
Sound, pi essure-tight, tin-bronze castings are de rigueur in chemical engineering processes. Accordingly, there has been considerable attention given to methods of achieving sound castings in the foundry (1,9, 14, S7, 47-49, 68). Nickel in combination with tin in copper-base alloys produces heat-treatable bronze castings. The influence of nickel on tin bronze has been studied rather extensively (56, 155-157). Classification of properties of bronzes (25) and of wrought tin brasses ( 8 9 ) have appeared in the literature. Bearing Materials. The bearink properties of tin bronzes (41) itrid tin base-bearing alloys (130) continue to be studied. Waug and Smith’s study of undercooling of the tin phase in a 10% tinin-aluminum alloy is of practical value in the manufacture of tinaluminum bearings (142). Others. Of particular interest to chemical engineers is information on the selection and use of fusible alloys (220, 121). Electrical contact elements that are substantially free from velding, deformation, and metal transfer have been patented (2%). These elements, which contain up to 10% tin, are reported to have a long life. BASIC RESEARCH
Under this category come all investigations dealing with tin that have as their objective a better understanding of natural laws. The Tin Research Institute has issued a publication covering equilibrium data for tin alloys (58). Equilibrium data on the following systems have also been published: Tin-indium-cadmium ( 5 3 ) ; tin sulfide-lead sulfide-lead (141); and binary systems of tin tetrabromide, tin tetraiodide, and trichlorosilane with some aliphatic ethers (126). Related investigations include the following studies: Solid solubility of tin in aluminum (6); thermodynamic study of the liquid tin-gold system ( 7 9 ) ; mechanical twinning in white tin (34); isothermal rate of solidification of tin ( I S 4 ) ; and factors influencing the transformation of white tin to gray tin have received attention in Soviet Russia (57). Lattice constants of
Vol. 43, No. 10
gray tin have been measured ( $ I ) , and the electrical properties of gray tin have been studied (17 , 2 3 ,S4, 78). Other studies of the properties of tin and tin alloys and compounds include: The role of diffusion in tin (43, 44) and tin alloys (40, 114); thermal behavior of tin (33, 7 0 ) and tin compounds (86, 127); viscosity of liquid tin and liquid tin-zinc alloys (146); magnetic properties of tin a t low temperature (18. 60,139); superconductivity of tin (1, 67, 91, 110, 144); radioactivity of tin (39,88); optical properties of evaporated layers of tin (4);and the effect of tin on the luminescence characteristic6 of zinc sulfide phosphors (61). REFLNING
Developments in refining include: A process for purifying impure tin that involves a replacement of tin in tin chloride with lead (13); a new partial reduction-leaching process for recovering low grade ores (45); flotation studies (62, 108, 2Sf) on cassiterite: concentration practice a t various tin producing areas (16,96,102); and a comprehensive description of tin extraction methods (92). LITERATURE CITED
(1) Allen, W. D., Dawton, R. H., el. al., Nuhwe, 166, 1071-2 (1950). (2) Ames, Bernard N., and Kahn, Noah A., Am. Fouadrymen’s SOC, preprint 5 M (1950). (3) Automotive I d s . , 103, 51, 58 (Sept. 1, 1950). (4) Avery, D. G., “Some Optical Properties of Evaporated Layers of Silver, Copper and Tin,” Phil. Mag., 41,1018-31 (October 1950). (5) Badaeva, T. A., and Kiiznetsova, R. I., Dolzlady Akad. N a u k S.S.S.R., 72, jO7-9 (May 21, 1950). (6) Baier, S. N-., and hlacnaughton, D. J. (to City Auto Stamping Co.), U. S. Patent 2,511,395 (June 13, 1950). (7) Bailey, G. L. J., and Watkins, H. C., Metal I d . 75, 551-4, (Dec. 30, 1949). (8) Bailey, G. L. J., and Watkins, H. C., Proc. Phys. Soc. (Lond o n ) , 63, part 5, KO. 365-B, 17. 350 (1950). (9) Baker, F. &I., Upthegrove, C., and Rote, F. B., Am. F o u n d r p men’s Soc., 58, 1.22-31 (1950). (lo) Beeghly, €1. F., J . Electrochemical SOC.,97, 152-7 (April 1950). (11) Bendix, Gordon H., U. S.Patent 2,455,726 (Dec. 7, 1948). (12) Bennett, P. S., J . Electrodepositors’ Tech. Soc., 26 (1950). (13) Billiton Maatxhappij, N. V., Brit. Patent 631,784 (Nov. 9, 1949). (14) BjBrkmann, P. O . , Brennert, S., Heutz, A., and Wallgram, A , , A\TeiLe Giesserei, 37 (now scr., Vol. 3 ) pp. 593-4 (Dec. 28, 1950). (15) Blanc, G., and Le Thomas, P. J., Fonder&, pp. 2257-66 (November 1950). (16) Blaskett, K. S., and Dunkin, H. H., Commonnrealth Scientific and Industrial Research Organization and the University of Melbourne Mebllurgy Department, Joint Invest. Yo. 374 (Dec. 22, 1949) (T177h148i). (17) Blum, A. I., a n d Goryunova, iY. A., Doklady Akad. Naiak S.S.S.R., 75, 367-70 (Nov. 21, 1950). (18) Borovick, E. S.,Ibid., 69, 667-9 (Dec. 21, 1949). (19) Bouton, G. hl., aiid Phipps, G. S. (to Bell Telephone Labora tories, Inc.), U. 9. Patent 2,508.488 (May 23, 1950). (20) Boyden, Charles, Sr.. Welding .I., 29, 907-9 (Oct. 1950). (31) Brownlee, L. D., Suture, 166, KO. 4328, 482 (1950). (22) Burgess, Charles O., Fou,ndry, 78, 76-9, 194, 196, 198, 202-3 (December 1950). (23) Buech, G., Rieland, J., and Zoller, H., Halc. Phgs. A c h , 23, 528-9 (Sept. 1, 1950). (24) Ihkl., 24, 49-62 (Feb. 15, 1951). (25) Cameron, A . M., and Johnson, S. R. it0 Continental Can Co.. Inc.), U. S. Patent 2,535,836 (Dee. 26, 1950). (26) Can. Mining .J., 72, 65 (March 1951). (27) Canning Trade, 72, No. 43, 20 (May 15, 1950). (28) Ibid., 73, No. 22. 12 (Dec. 18, 1950). (29) Ibid., 73, No. 31, 14 (Feb. 19, 1951). (30) Carnegie-Illinois Steel Corp., Brit. Patent 640,064 (July 12, 1950). (31) Carouge, ilteliers, S. A. de, Swiss Patent 268,226 (Aug. 1, 1950). (32) Cheftel, H., Pien, J., Fouasson, R., et. d.,Ann. fals. et/raudea. 42, 168-74 (1949). (33) Childs, B. G., and Weintroub, S., PPOC. Phg.9. SOC.63, Sec. 13, pp. 267-77 (April 1, 1950). (34) Clark, R., Craig, G. B., and Chalmers, B., Acta Crystallogmphica, 3, 479 (November 1950). (35) Clawaon, John H. (to General Electric Go.), U. S. Patent 2,498,485 (Feb. 21, 1950).
October 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
(36) Cuthbertson, J. W., J. Electrodepositms’ Tech. Soe., 25, 81-3 (1950). (37) Dick, James G., Can. Metals, 13, 22, 24, 26, 28-9, 43 (October 1950). (38) DiGiulio, Armand, U. 8. Patent 2,508,501 (May 23, 1950). (39) Duffield, R. B., and Langer, L. M., Phys. Rev. 76, 1272-3 (1949). (40) Duwez, Pol, Powder Metallurgy Bull., 4, 144-56 (October 1949). (41) Eckert, Fr., Pro-Metal, 3, 649-53 (1950). (42) Fedot’ev, N. P., Vyacheslavov, N. M., and Orlova, E. I., J . Applied Chem. (U.S.S.R.), 23, 380-4 (April 1950). (43) Fensham, P. J., Australian J . Sci. Research, sei. A, 3, 91-104 (March 1950). (44) Ibid., PP. 105-8. (45) Fink, Colin G., and Strauss, Howard J., Eng. Mining J., 151, No. 12, 96-7 (December 1950). (46) Forker, G. M.. U. 8. Patent2,522,937 (Sept. 19, 1950). (47) Frear, Clyde L., Foundry, 78, 94-5, 213-14, 216, 218 (June 1 QKnl A Y Y Y , .
(48) Ibid., 78, 76-9, 199-203 (July 1950). (49) Ibid., 78,76-7,182-9 (August 1950). (50) Fritz, James J., Gonaalez, Oscar D., and Johnston, Herrick L., Phys. Rev., ser. 2, 80,894-9 (Dec. 1, 1950). (51) Garlick, G. F. J., and Mason, D. E., P>oc. Phys. SOC.,62, sec. A, 817-22, (Dec. 1, 1949). (52) Gaudin, A. M., and Schuhmann, R., Jr., Mineria bolivhna, 4, NO. 36, 15-23 (1947); 5, NO. 37, 9-13 (1948). (53) Gebhmdt, Erich, 2. Metallkunde, 40, 437-40 (December 1949). (64)George, Nelson C., and Haab, Rolf C. (to Carnegie-Illinois Steel Corp.) U. S. Patent 2,497,164 (Feb. 14, 1950). (65) Glock, Charles E. (to Crown Cork and Seal Co.), Ibid., 2,513,859 (July 4, 1950). (56) Goederitz, A. H. F., Metall., 4,495-8 (December 1950). (57) Goryunova, N. A., Doklady Akad. Nauk S.S.S.R., 75, 5 1 4 , (Nov. 1, 1950). (58) Greenfield, L. T., and Bowden, J. S., Tin Research Institute, Greenford, Middlesex, England, TN793 T49e (1949). (59) Grymko, S. M., and Jaffee, R. I., Materials and Metho&, 31, 59-60 (March 1950). (60) Halls, E. E., Electroplatino and Metal Finishing, 3, 4 9 3 4 (September 1950). (61) Halls, E. E., Metallurwia, 41, 68-73 (December 1949). (62) Harris, A. W. (to American Steel & Wire Co. of N. J.), U. 6. Patent 2,543,365 (Feb. 27, 1951). (63) Hoare, W. E., Foundry Trade J., 89, 411-14, 427, (Nov. 23, 1950). (64)Hoare, W. E., J . Inst. Production Engrs., 30, No. 3, 104-33 (March 1951). (65) Hoare, W. E., Sheet Metal Inds., 28, No. 287,231 (March 1951). (66) Hoare, W. E., “Tinplate Handbook,” Greenford, Middlesex, England, Tin Research Institute, 1950. (67) Hudaon, Ralph P., Phys. Rev., 79,883 (1950). (68)Hull, Daniel R., “Casting of Brass and Bronze,” Cleveland, Ohio, American Society for Metals, 1950. (69) Hull, Richard 0. (to E. I. du Pont de Nemours & Co.), U. S. Patent 2,612,719 (June 27, 1950). (70) Hulm, J. K,, Proc. Roll. SOC.(London),ser. A, 204, 98-123 (Nov. 22, 1950). (71) International Tin Study Group, Statement on Position and Prospects of Tin Industry (May 1950). (72) Ibid., “Statistical Year Book 1949,” 1950. (73) Ibid., “Tin--1949-1950,” 1950. (74) Jernstedt, George W. (to Westinghouse Electric Corp.), U. S. Patent 2,530,967 (Nov. 21, 1960). (75) Johnson, W. R., Kinney, L. C., and Park, John M., Yearbook American Iron and Steel Institute, pp. 495-514, 1949. (76) J . Electrochemical SOC.,97,472-4 (December 1950). (77) Kadell, Alfred E., Steel, 127,72 (July24, 1950). (78) Kendall, J. T., Proc. Phys. SOC.,63, sec. B, 821-2 (Oct. 1, 1950). (79) Kleppa, 0. J., J. Am. Chem. SOC.,72, 3346-52 (1950). (80) Kohman, Edward F., Ind. Eng. Chem., 42, 1578-81 (1950). (81) La Crue, Mariano Tomeo, and Martinez, Ramon, Natl. Paint, Varnish Lacquer Assoc., No. 157, p. 96 (May 1950). (82) Langton, J. W., Sheet Metal Inds., 28, pp. 137-140, 146 (February 1951). (83) Lowenheim, F. A,, (to Metal and Thermit Corp.). U. 6. Patent 2,528,601 (Nov. 7, 1950). (84) Lowenheim, F. A., Wire and Wire Products, 24, 1117-20 (December 1949). (85) Lowenhim, F.’A., and Hirschland, Herbert E., Ibid., 24, 102832, 1068-9 (November 1949). (86) Lyon, D. N.. and Geballe, T. H., Rev. Soi. Instruments. 21, 76970 (August 1950). (87) McCoy, James P. A., (to Allis-Chalmers Manufacturing Co.), U. S. Patent 2,482,923 (Sept. 27, 1949).
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(88) Mallory, E, C., and Pool, M. L., Phys. Rev., 76, 1454-7 (1949). (89) Materials and Methods, 32, 85 (September 1950). (90) Ibid., 33, 144 (March 1951). (91) Maxwell, Emanuel, Phys. Rev., 79, 173 (1950). (92) Mertens, G., Metall, 4, 14-18 (January 1950). (93) Metalloberjlache, 3, ser. B, 19-21 (February 1951). (94) Metallurgia, 42, 131-3 (August 1950). (95) Metal Progress, 58, 546, 548, (October 1950). (96) Michell, F. B., Mining World, 12,34-5,37 (September 1950). (97) Miller, Mike A., U. S. Patent 2,286,298 (June 16, 1942). (98) Montoro, Vincenzo, MetaElurgia Ital., 41, 279-86 (Nov.-Dec. 1949). (99) Moses, Saul, Natl. Paint, Varnish, Lacquer Assoc., No. 163, 227 (November 1950). (100) Nachtman, John S., U. S. Patent 2,490,700(Dec. 6, 1949). (101) Natl. Lithographer, 57, 38-9, 78-80, (December 1950). (102) Ni, T. T., and Sun, Shiou-Chuan, Tram. Can. Inst. Mining Met., 54, 40-3 (1951). (103) Noltingk, B. E., and Neppiras, E. A., Nature, 166, 615 (Oct. 7 , 1950): (104) Parhnson, N., J. Electrodepositors’ Tech. Soc., 27, No. 4 (1951). (105) Pessel, Leopold (to Radio Corp. of Bmerica), U. S. Patent 2,547,771 (April 3, 1951). (106) Phipps, G. S., Bell Lab. Record, 28, 295-7 (July 1950). (107) Prust, A. F. (to Republic Steel Corp.), U. S. Patent 2,503,217 (Apr. 4, 1950). (108) Pryor, E. J., and Wrobel, S. A., Trans. Inst. Mining Met., 60, pt. 6,201-37 (1950-51). (109) Puttick, K. E., Metallurgia, 41, 120-1 (1949). (110) Rademakers, A., Physica, 15, 849-59 (October 1949). (111) Reeve, Howard T. (to Bell Telephone Lab., Inc.), U. S. Patent 2,503,664 (April 11, 1950). (112) Roberta, C. W., Metallurgia, 42, 65-8, (July 1950). (113) Rodgers, H. C. (to Tennessee Coal, Iron, and Railroad CO.), U. S. Patent 2,533,048 (Dec. 6, 1950). (114) Rooksby, H. P., J . Electrodepositms’ Tech. SOC.,26, NO. 8 (1950). (116) Itooksby, H. P., Ibid., 27, No. 5 (1951). (116) Schumacher, Earle E., J. Inst. Metals, 78, part 1, 1 (September 1950). (117) Schweikher, E. W. (toE. I. du Pont de Nemours & Co.), U.5. Patant 2,407,579 (Sept. 10, 1946). (118) Scott, B. E., Iron Age, 167,59-62 (Jan. 18,1961). (119) Seabright, L. H., Metal Finishing, 48, No. 10, 54-6, 72 (1950). (120) Seeds, 0. J., Materials & Methods, 32, 64-8 (September 1950). (121) Seeds, 0. J., Western Mach. and Steel World,41, 82-3 (April 1950). (122) Shuttlewort, R., and Bailey, G. L. J., Discussions Faraday SOC., No. 3, 16, (1948). (123) Silman, H., and Wernick, Dorothy, J . Electrodepositors’ Tech. SOC.,25, 175-87 (1950). (124) da Silva, L. C. C., and Mehl, R. F., J. Metals, 188, 1219-20, (October 1950). (125) Singh, D., and Siddhanta, N. N. S., J . Indian. Chem. Soc., 26, 471-6 (1949). (126) Sisler. Harry H., Schilling, Edw. E., and Groves, Warren O., J. Am. C h a . Soc., 73, 426-9(1951). (127) Spandau, H., Angew Chem., A60,73-4 (1948). (128) Steel, 127, 118, 120 (Nov. 20, 1950). (129) Stumbock, Max J. (to Baker & Co., Inc.), U. 5. Patent 2,486,341 (Oct. 26, 1949). (130) Tabor, D., Engineer, 186, 117-9 (July 30, 1948). (131) Thompson, A. Graham, Mining J., 234,625-7 (June 16, 1950). (132) Tin, Statistical Supplement, p. 11 (July 1951). (133) T i n Printer, Natl. Paint, Varnish, Lacquer Assoc., No. 160, 169 (August 1950). (134) Turnbull, D., J. Chem. Phys., 18, 768-9 (May 1950). (135) Vanick, James S., Foundry, 78,80-3,211-12, (December 1950). (136) Ibid., 79, 102-7 (February 1951). (137) Zbid., 79, 130-3, 278-9 (April 1951). (138) Vaurio, V. W., Corrosion, 6, No. 8, 260-7 (1950). (139) Verkin, B. I., Laizarev, B. G., and Rudenko, N. S., Doklady Akad. Nauk S.S.S.R., 69, 773-6 (Dec. 21, 1949). (140) Vieno, C. A., U. S. Patent 2,548,690 (April 10, 1951). (141) Vogel, Rudolf, and Zastera, Anton, 2. Metallkunde, 41, 14-19 (January 1950). (142) Wang, Chih-Chung, and Smith, Cyril Stanley, Trans. Am. Inst. Mining Met. Engrs., 188, 136-8 (January 1950). (143) Watkins, H. C., Metallurgia, 42, 372-6 (December 1950). (144) Webber, R. T., and Steele, M. C., Phys. Rep., 79,1028-9 (1950). (145) Wire Id., 17, 115 (February 1950). (146) Yao, T. P., and Kondic, V., Nature, 166, 483 (Sept. 16, 1950). (147) Zapffe, C. A., and Haslem, M. E., Plating, 37, 610-13 (June 1950). RECEIVED July 26, 1951.
