CEMENTS

Improved reinforced furan resin linings bonded to steel are serving as substitutes ..... square inch, and the tensile strength of the cement is about ...
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CEMENTS C. R. PAYNE, Electro Chemical Supply and Engineering Co., Emmaus, Pa. 1000 square feet of floor and 100 square feet of pump foundations exposed to chlorinated hydrocarbons and hydrochloric acid, The installation is open to the atmosphere and therefore is subjected to wide temperature changes. The use of furan cements in England has been reported (57, 64, 97). The composition, application, and industrial uses are ap-. proximately the same as in the Dnited States.

Improved reinforced furan resin linings bonded to steel are serving as substitutes for corrosion-resistant metal alloys in the construction of reactors, tanks, towers, and fume ducts. Rapid progress has been made in perfecting cold-setting epoxy resin cements for use in tbe electrical industry. Interesting data are reported on the fundamental factors influencing the tervick life of acidproof brick linings in sulfite digesters. A number of improvements have been made in the physical and chemical properties of acidproof cements, and new techniques of application --. have been developed to extend the range of their industrial usee.

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HE serious shortage of corrosion-resistant metal alloys has stimulated fvrther work on furan resin linings bonded to steel or concrete in the construction of acidproof chemical process equipment. The need of a substitute for alloys is particularly acute for lining equipment handling organic solvents as well as acids or alkalies. FURAN RESIN CEMENTS

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As reported in the previous annual review, reactors handling organic solvents and hydrochloric acid a t 350" F. have been in continual service for over 2 years without maintenance costs. These reactors are lined with a '/(-inch thick layer of furan cement reinforced with glass cloth and bonded directly to the steel shell. This impervious layer is protected with 9 inches of acidproof brick bonded with furan cement. These reactors are approximately 5 feet in diameter by 17 feet high. Since that time a number of units have been lined in this manner, the largest being 20 feet in diameter by 22 feet high. I n some instances a thin cushion of synthetic rubber is interposed between the furan layer and the brick lining. Until recently the use of furan resin cement linings reinforced with glass cloth or expanded metal lath were not considered satisfactory a t temperatures exceeding 175' F. unless further protected and supported by a brick lining (9). Although temperatures above 175' F. did not cause disintegration of the furan resin, difficulties were encountered because of differential expansion of the steel and resin unless a brick lining was used. It was determined that most of the trouble could be eliminated by improving the physical properties of the resin, careful control of the curing time, and developing special techniques of applying the lining to reduce stresses. Pumps and valves have also been lined successfully with proper attention to these factors (61). By varying the composition, cements have been developed having a shrinkage on setting of less than 0.1% and a coefficient of thermal expansion which closely approaches that of steel over a temperature range from 20" to 250' F. Increased plasticity and adhesion are obtained by blending with other resins-for example, furfuryl alcohol-formaldehyde liquid resins may be blended with epoxy resins, modified phenolics, polybutadiene, polyvinylbutyral (42), melamine resins (25, 9U), p-toluidine resins (49), urea resins (14), asphalt (21), and condensation products of furylethylene derivatives and aldehydes (24). All the furan cements are dark in color. I t is reported that clear resins may be obtained by condensation of furfuryl alcohol with formaldehyde and phenol in certain proportions (28). As reported in the previous review, % number of trial installations were made using fabric-reinforced furan resin cement coverings I/A-inch thick on concrete pump foundations and over concrete floors where the cost and weight of a standard acidproof brick floor was excessive. One particular trial installation that has been in succesjful service for 1 year, involves approximately

PHENOL-FORMALDEHYDE RESIN CEMENTS

The Buna N-phenolic blends have advantages as to shock resistance (34),and blends of epoxy reins with phenol-formaldehyde resins possess unusual plasticity and resistance to mechanical impact and chemical attack (35). Improved properties were obtained by modifying phenol-formaldehyde resins with melamines (84). .4 phenolic cement for joining brake linings to metallic supports was developed (86). ii nylon-filled phenolic cement has high electrical resistivity and resistance to mold growth (59). A new cement having good bond strength at high temperatures is produced from a modified phenolic and a thermoplastic resinous polymer (68). A method of producing odorless phenoi-fornialdehyde cements has been reported (98). Compositions of modified phenol-formaldehyde resin cements and their use in sealing oil wells are described (6, 4 7 ) . iz new casting phenolformaldehyde cement has been used satisfactorily for producing pipe, fittings, pumps, and valves. The greatest chemical resistance is obtained by using a resin produced from 1 part phenol and l l / p parts formaldehyde. Some of the fundamental principles of design for this type of work are given (781. Of a number of coatings tested for their resistance to sulfur-containing crude petroleum, hydrogen sulfide, weather, and abrasion, a modified phenolformaldehyde type was best (67). Acid-resisting resin cements made from cashew nutshell oil are used to a much greater extent in England than in the United States (97). The acid resistance is similar to that of phenolformaldehyde cements, but the main value is in the high resistance to caustic alkali solutions a t elevated temperatures. The resistance to organic chemicals is relatively poor and inferior to phenol-formaldehyde cements, Cashew nutshell oil cements catalyzed just before use with 16% paraformaldehyde were satisfactory for bonding wood (69), and improved properties were obtained when they were mixed with rubber (88). Allyl etheis of phenolic cashew nutshell liquids mixed with paraformaldehyde and produce a cement which hardens a t room temperature (&I), polymers of cashew nutshell oil are copolymerized with styrene and set a t room temperature with paraformaldehyde (41 ). SULFUR CEMENTS

An interesting series of cements and sealing materials have been developed from polysulfide liquid polymers. The cement vulcanizes or sets a t room temperature by the addition of catalysts such as metal peroxides. These cements have low shrinkage and good adhesion and are satisfactory for use a t temperatures of -70" to 300" F. They are resistant to oils, aliphatic and aromatic fuels, and many chemicals. In another modification, a cement of high solids is mixed with furfural and acidic catalysts. Latex ce-

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Vol. 43, No. 10

INDUSTRIAL AND ENGINEERING CHEMISTRY

I n s t a l l a t i o n of Acidproof Brick Lining Joined w i t h Furan Resin Tanks, 330 feet long by 8 X 4.5 feet are used for continuous pickling of steel with 2 5 % sulfuric acid

ments have proved satisfactory for the coating of steel tanks used for the storage of sour crudes (27,65). The reaction of castor oil with sulfur produced a cement satisfactory for sealing surfaces in internal combustion engines, leaks in gasoline tanks, and for joining glass to rubber or metal (91). An interesting investigation showed that the surface tension of sulfur may be lowered appreciably by the addition of iodine (86). SILICATE CEMENTS

It is well known that silicate cements are subject to erosion, particularly by weak acids or neutral solutions, and are liable to “wick action” (37, 97). These properties have resulted in their replacement for many industrial uses by resin or sulfur cements. Hon-ever, silicate cements are the only type that withstand hot concentrated nitric or sulfuric acids. It is reported that one silicate cement, used in England, is accelerated with ethyl acetate and is much less liable to “wick action” than those accelerated with sodium silicofluoride which is used here. The disadvantage of using ethyl acetate is its flammability and anaesthetic action (97). The gelation of sodium silicate with sulfuric acid, hydrochloric acid, ammonium sulfate, and sodium aluminate was studied (66). A silicate cement consisting of graphite and sodium silicate has proved satisfactory for protection of annealing box covers made of plain carbon steel; the service life of the cover is doubled (70). A heat- and chlorineresistant cement for joining glass surfaces is made by mixing kieselguhr with condensed ethyl silicate and chlorinated rubber (105). BITUMINOUS CEMENTS

The use of asphalt materials in chemical plants has been reviewed (12). As reported in the previous review, cold maslics modified with synthetic resins and rubber are being used in large volume for the protection of the outside of chemical equipment,

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particularly equipment exposed to the weather and/or corrosive chemicals. This same type cement when mixed with lightweight insulating materials, such as cork, produces a weatherproof insulation. A number of Hortonspheres used for the storage of butane over a 2-year period have been successfully insulated by applying a ‘/Anch layer of this type mastic over the outer surface with a special spray gun. Powdered or reclaimed rubber mixed with asphalt has produced an excellent road cement (87). A4sealing composition for expansion joints is made of coal tar pitch and a copolymer of butadiene and acrylonitrile. This expansion joint has high resistance to solvents and chemicals ( 6 6 ) . Minor amounts of alkyiamines, alcohols, or organic acids, when mixed with solvent blend bituminous cements, retard viscosity rise with time (45). HYDRAULIC CEMENTS

The literature pertaining to the agents and causes of the corrosion of portland cement concrete was reviewed (11, 73). The use of volcanic ash as the aggregate was found to prolong the life of concrete floor toppings and other structures exposed to acids ( 9 , 46). Powdered calcite as an admixture to the cement was reported to increase the resistance of concrete to salt water, weather, and acids (S). Protective coatings for concrete exposed to acids were discussed (4). The problem of protecting concrete against attack by the sodium and magnesium sulfate of alkali soils was reviewed (M), and the beneficial effects of entrained air against the attack by such salts was reported (18, 62). A theoretical discussion of the manner in which entrained air protects concrete against freezing included an effort to calculate the amount of entrained air required to produce frost-resistant concrete (76). It was shown that leakage of alternating current into concrete is not harmful and that direct current may increase the bond with the steel reinforcing ( 4 5 ) . Three investigations were made of the

October 1951

INDUSTRIAL AND ENGINEERING CHEMISTRY

value of concrete in shielding against gamma rays and neutrons (19, 58,104). A mixture of cement, scrap iron, and limonite ore is as efficient m water in slowing down and capturing neutrons and has sufficient density to be effective in absorbing gamma radiation. The preparation and properties of concretes for use at high temperatures were studied for data on the preparation and use of castable refractories (44). The various uses of high-alumina cement as a construction material in the chemical industry and the chemical resistance of these cements is reported (48). Supersulfated cements are produced by grinding together granulated blast furnace slag, calcium sulfate, and small quantities of portland cement clinker; this is much more resistant to sulfate solutions than portland cement (97). EPOXY CEMENTS

Rapid progress has been made in the development of new cements from epoxy resins. These cements may be compounded to cure a t room temperature or a t elevated temperatures; they make possible the joining of metals, ceramics, glass, and plastics, together and to each other, without the use of pressure. I n metal-to-metal bonds, these resins provide a joint which can be the equivalent of riveting, welding, or soldering. Modifications of these products are used as acid-resisting cements and as encapsulation for embedding circuits and electrical components for protection against weathkr. moisture, and as insulation. The coldsetting compositions are also used for capacitor, resistor, and transistor embedding material in coils, transformers, and subminiature radio components (76, 99, 100). Glass cloth-reinforced epoxy resin cements have estimated flexural strengths as high as 85,000 pounds per square inch (89). Other Epoxy compositions are described ( 7 , 16,36). MISCELLANEOUS CEMENTS

Cements made by mixing rubber latex with hydraulic cements are used in England for the construction of acid resistant floors to a far greater extent than in this country (97). The adhesion of this cement to acidproof brick is of the order of 300 pounds per square inch, and the tensile strength of the cement is about 400 pounds per square inch. The plasticity of the cement is sufficient to absorb severe vibration without cracking or losing bond to the ceramic units. The physical and chemical characteristics of various compositions of natural and synthetic rubber latex, synthetic latices of polyvinyl chloride mixed with aluminous and portland cement are described (57, 96). A n interesting use of a new neoprene cement to repair and seal eroded condenser tubes and sheets has been perfected. The process costs less than 5% of a retubing job which would otherwise be necessary ($5). Neoprene cements have also been used successfully to seal and protect wood tanks used for storage and processing of acids (8, I d ) . A new type adhesive is produced from thiophene, formaldehyde, and resorcinol. The cement has high impact strength, low distortion values, and good resistance to alkalies (6). A cement having good electrical resistance is produced from melamine, aniline, and formaldehyde (60). A cement satisfactory for weterand acid-resistant masonry is produced from potassium chloride, sodium silicofluoride, and quartz powder (86). A new cement for bonding rubber or synthetic rubber to metals consists of a mixture of partly dechlorinated, chlorinated natural or synthetic rubber, and the product of the reaction of hypochlorous acid on rubber (8.3). Carbon linings for a carbon-hearth furnace were cemented with a carbon-base cement (5.9). A new cement based on fly ash, portr land cement, gypsum, 9nd rock wool has found wide application in power plants because of its insulating, adhering, and finishing properties (77). A cement has been developed for bonding sheets of vinyl or vinylidene halide polymers to metal surfaces. The

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cement consists of vinylidene chloride, acrylonitrile, and tetraethyldisulfide (79). IMPERVIOUS MEMBRANES

Usually, in the construction of acidproof brick floors, the concrete sub-base is protected first with a l/rinch thick asphalt membrane and then covered with acidproof brick joined with resin or sulfur cement. I n some instances, where solvents are spilled on the floor, an impervious membrane of furan resin cement reinforced with glass cloth is laid down before installing t h e brick floor. The use in Germany of polyisobutylene sheet, and in England the use of polythene or polyvinyl chloride sheet instead of asphalt has been described (37). The use of rigid and plasticized polyvinyl chloride sheet linings for chemical equipment has been described (60). Fume ducts, tanks, tank inserts, fans, pumps, and valves are made from the rigid sheet which is produced in thicknesses up to 2 inches by a special process. Copolymers of butadiene and styrene are suitable for higher temperatures than natural rubber, but the most stable is the isobutylenebutadiene copolymer (65, 81). Polystyrene, polyethylene, and polyvinyl chloride have good resistance to 48% hydrofluoric acid (80). D a t a on the chemical, mechanical, and electrical properties of chlorotrifluoroethylene have been published (50, 88). Polymerized tetrafluoroethylene, chlorotrifluoroethylene, and interpolymers of these two materials are plasticized with fluorinated hydrocarbon oils (17). A small amount of finely divided sodium aluminum silicate incorporated in neoprene cements imparts dimensional stability (61). Although the subject of much research, a satisfactory method of cementing polyethene or Teflon sheet to metal has not been developed. Flame spraying of polythene has been attempted with varying success. The use of polythene-isobutylene blends are satisfactory for someuses (53,7$). A cement for high temperature seals for vacuum joints is produced by treating a dimethyl silicone with a boron compound and adding fillers to the product (105). Other siloxane resin compositions suitable for use as cements have been described (10). INDUSTRIAL APPLICATIONS

An interesting study of the factors influencing the service life

of acidproof brick linings in sulfite digesters has been published (98). T o maintain a balance between tensile and compressive stresses in a brick digester lining so that a tight seal between lining and shell is always maintained, it is necessary to consider tho “residual” compression which normally builds up in a lining. The residual stress develops relatively slowly to a point of approximate constancy and depends on the water swelling and elasticity of the materials. The combined stress caused by water swelling and thwmal expansion should a t all times be great enough to exceed all influences tending to cause tension but should not be so great as t o exceed the strength of the lining or lining materials. Actual temperature measurements taken a t numerous points in a digester lining and shell show the variations in the temperature gradients throughout the cooking cycle and under varying conditions. The results of this work emphasize the need for consideration of such factors as external temperatures, cold air drafts, installation temperatures, sudden heating or cooling of the face of the lining, and other influences which frequently and alone might not be considered important. Whereas the lining materials are chosen and the lining designed so that sufficient safety is incorporated to compensate for some irregularities, nevertheless an accumulation of irregularities all acting to increase the effects in one direction may reduce the service life of a lining or cause excessive maintenance. On the other hand, general recognition of these less obvious factors should aid in extending the average life of digester linings even beyond ’the present-day average. The corrosion and lining of sulfate digesters have been described. It was observed that digesters installed in 1947-48 are giving much shorter service than older units despite identical

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INDUSTRIAL AND ENGINEERING CHEMISTRY

Vol. 43, No. 10

Weatherproof Insulation on Hortonsphere Used for Storage of Butane Insulation is 0.5-inch thick, asphalt-synthetic rubber cement containing granulated cork

steel specifications ( 1 6 , 63). Calcium-base sulfite liquor after evaporation to 62.7% solids was burned successfully in a modified Sterling boiler (54). Stacks for the disposal of TTaste acid gases from paper inills have been constructed of concrete and lined with 4 inches of acidproof brick joined u i t h furan resin cement. .4n asphalt membrane is used between the brick lining and the reinforced concrete stack. Acidproof brick-lined equipment used to produce phenol by sulfonation includes tanks used in the neutralizing system and the acidification towers (66). Paints, pIastics, and floor materials lvere evaluated for their susceptibility t o contamination and subsequent decontamination for use in radiocheinical laboratories (94). An acidproof brick-lined reactor for the continuous production of aliphatic polysulfonyl chlorides was described (20). The corrosion of lead linings in rayon spin bath evaporators is due mainly t o electrochemical effects caused by lack of homogeneity in the lining and local concentration differences in the bath liquor being evaporated (58). Acidproof brick-lined evapoi ators have been used nithout this difficulty. The plant for the recovery of sulfur dioxide a t the Consolidated Mining and Smelting Co. of Canada, Ltd., has been described ( 5 7 ) . Cooling towers, 10 x 10 X 24 feet, Pachuca-type acidifiers 8 feet in diameter by 10 feet, eliminators 9 feet in diameter by 22 feet, coke filters 8 X 10 X 5 ~ / feet, 4 and drying towers 7 X 7 X 48 feet are all lined vAth acidproof brick. Either lead or bituminous materials are used behind the brick lininp nhich is joined with acidproof cement. Information on the chemical and physical propel ties of acidproof clay arid shale brick were published (%, 59, 96). A survey was made on the use of ceramics for nuclear reactors (81). Impervious carbon liners for pipes and vessels are ma,de of carbon shapes impregnated ~ i t ah salt solution that nil1 react with the

acid to produce an insoluble salt in the pores of the caiboii liner ( 1 ) . Kexv types of carbon for lining chemical equipment have been described ( 9 , 29, 71, ?.& 101,108). A satisfactory method of joining straight end sections of pipe produced from caibon, phenol-formaldehyde I esin, or furan resin has been pcifcctcd, thus eliminating the necessitl of using metal flanges in marly instances. Tanks satisfactory foi handling invert sugar solutions having a pH of 4.0 were satisiacto~ilyprotected with six coats of phenolic resin cement containing 40% solids (28). ACKNOWLEDGMEIIT

The section on Hydraulic Cements was prepared by W. C. IIansen, Universal iitlas Ceiiient Co. LITERATURE CITED

Abraham, hlbei t. Jr. (to Standard Oil Developmelit (yo.), U. 8. Patent 2,530,320 (Nov. 14, 1950). i2hrends, I., Drecki, A,, and Koteoki, W., Cement (U’amnci), 4, 44-6 (1948). Anon., Ckem. A g e , 61, 128 (1949). Anon., Batir, S o . 5, 46 (1950). Barkhuff, Raymond A , , and Debling, Lawrence M. (to Moiisanto Chemical Co.), U. S. Patent 2,538,753 (Jan. 2 3 . 1951). Barkhuff, Raymond A , Jr. (to Monsanto Chemical Co.), E . Y. Patent 2,513,614 (July 4, 1950). Bradley, Theodore, F. (to Shell Development C o . ) , U. H. Patent 2,500,600 (March 14,1950). Blohm, C. L., and Frazier, H. D., Chem. Eng., 57, S o . 9, 140 (1950). Bodvan-Griffith, C. L., Presented a t conference of Soc. Chenr. Ind., Birmingham L-niversity (April 18-20, 1950). Braley, Orville B. (to Dow Corning Corp.), V. S . Patent 2,504,388 (April 18, 1950). Brocart, J., Techniques et Architecture, 1,70-2 (1948).

October 1951

INDUSTRIAL AND ENGINEERING CHEMISTRY

(12) Broome, D. C., Presented a t Conference of SOC.Chem. Ind., Birmingham University (April 18-20, 1950). (13) Campbell, W. G., and Packman, D. F., Ibid. (April 18-20, 1950). (14) Carlin, Frank, Jr. (to American Cyanamid Co.), U. S. Patent 2,510,496 (June 6, 1950). (15) Ciba Ltd., Swiss Patent 264,818 (Feb. 1, 1950). (16) Collins, T. T., Jr., Paper Z'rade J., 130, 90.21, 32-4-36, 38; NO.22,20-2 (1950). (17) Compton, John D., Justice, Joseph M'., and Irwin, Carl F. (to E. I. du Pont de Nemours & Co.), U. S. Patent 2,510,078 (June 6,1950). (18) Dahl, L. A., Proc. Am. ConcreteInst., 46, 257-72 (1949). (19) Dealno, V., and Goodman, C., J . Applied Phys., 21, 10407 (1950). (20) Dietrick, S. R., Lockwood, W. H., and Whitman, N. (to E. I. du Pont de Kemours & Co.), U. S. Patent 2,462,730 (Feb. 22,1949). (21) Dillehay, E. R. (to Richardson Co.), U. S. Patent 2,501,995 (March 28,1950). Dinelli, Rino, and Mostardini, Rino, Italian Patent 454,618 (Jan. 28, 1950). Dunlop, Andrew P., and Washburn, Ernst L. (to Quaker Oats Co.), U. S. Patent Appl. 604-081; Oficial Gaz., 628, 1530 (1949). Dunlop, Andrew P., and Washburn, Ernst L., U. S. Patent 2,527,714 (Oct. 31,1950). Ellers, Saul, U. S. Patent 2,452,557 (Feb. 23, 1948). Fanelli, R., J . Am. Chem. Soc., 72, 4016-18 (1950). ENG.CHEM.,42, KO.11, Fettea, E. M., and Jorczak, J. S.,IND. 2217-23 (1950). Foelsch, H. W., Corrosion, 6 , No. 8, suppl. 1 (1950). Franke, E., Werkstope u. Korrosion, I , 254-60 (1950). Frey, Sheldon E., Gibson, Donald J., and Lafferty, Robert H., Jr., IND. ENG.CHEM.,42, No. 11,2314-17 (1950). Geller, R. F., Nucleonics, 7, No. 4, 3-17 (1950). German, W. L., and Ratcliffe, S. W., Presented a t Conference of SOC.Chem. Ind., Birmingham University (April 18-20, 1950). Goldberg, Bernard, Corrosion, 7, 47-50 (1951). Goss, W., Modern Plastics, 28, No. 7,100-2 (1951). Greenlee, Sylvan 0. (to Davoe & Raynolds Co., Inc.), U. S. Patent 2,521,911 (Sept. 12, 1950). Ibid., 2,510,885 and 2,510,886 (June 6, 1950). Griffiths, L. H., Presented a t Conference of SOC.Chem. Ind., Birmingham University (April 18-20, 1950). Gugelot, P. C., and White, M. G., J . Applted Phys., 21, 369-79 (1950). Halls, E. E., Plastics (London), 15, 194-6 (1950). Harvel Corp., British Patent 627,478 (Aug. 10, 1949). Ibid., 636,695 (May 3, 1950). Harvey, Mortimer T. (to Harvel Research Corp.), U. S.Patent 2,508,025 (May 16, 1950). Haslett, A,, Proc. Am. ConcreteInst., 46, 75 (1949). Heindl, R. A., and Post, Z. A., J . Am. Ceram. Soc., 33, 230 (1950). Hoiberg, Arnold J., IND. ENG.CHEM..43, No. 6, 1419-23 (1951). Howard, E. Lorenao, Concrete, 56, No. 1, 16-18 (1948). Hower, Wayne F., World Oil, 130, No. 6, 96-8, 101-2 (1950). Huasey, A. V., and Robson, T. D., Presented a t Conference of Soc. Chem. Ind., Birmingham University (April 18-20, 1950). Imoto, Minori, and Asao, Chiyo, J . SOC.Chem. I n d . J a p a n , 50,132-3 (1947). Jaray, F. F., Presented a t Conference of Soc. Chem. Ind., Birmingham University (April 18-20, 1950). Jennings, Alfred J., and Luzena, Verl E . (to E. I. du Pont de Nemours & Co.), U. S. Patent 2,508,262 (May 16, 1950). Johnson, C. P., J . Metals, 188, 752-3 (1950). Johnson, Thomas C., T A P P I , 33,481-4 (1950). Jolley, R. S., and Rogers, C. E., Paper Trade J., 131, No. 20, 25-6,28-30 (1950). ENG.CHEM.,43, 324-8 Jorcsak, J. S.,and Fettes, E. M., IND. (1951). Kenyon, Richard L., and Boehmer, N., Ibid., 42, No. 8, 144655 (1950). King, R. A., Ibid., 42, No. 11, 2241-48 (1950). Kleinert, Th., and Pospischill, F., M i t t . Chem. Forsch., Inst. I n d . Osterr., 2 , 4 5 4 (1948). Koenig, John H., Materials & Methods, 32, No. 3, 69-84 (1950).

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(60) Lindenfelser, Richard, and Gabrowski, Joseph (to American Cyanamid Co.), U. S. Patent 2,526,885 (Oct. 24,1950). (61) McFarland, R., Corrosion, 7, No. 4, 1-2 (1951). (62) McMillan, F. R., Stanton, T. E., and Hansen, W. C., Portland Cement Assoc. Res. Lab. Bull., 30 (December 1949). (63) McNamee, J. P., Chem. Eng., 57, No. 11, 128 (1950). (64) Marsden, L., Presented a t Conference of SOC.Chem. Ind., Birmingham University (April 18-20, 1950). (65) Merrill, Reynold C., and Spencer, R. W., J . Phys. & Colloid Chem.. 54. 806-12 (1950). . --, (66) Miller, Herman C. (to United States Rubber Co.), U. S. Patent 2,536,611 (Jan. 2, 1951). (67) Moore, John C., and Phelps, Neil T..Oficial Diuest Federation Paint and Varnish Clubs, No. 280, 381-3 (1948). (68) Nagel, Fritz J. (to Westinghouse Electric Corp.), U. S. Patent 2,542,048 (Feb. 20, 1951). (69) Narayanamurti, D., and Jain, N. C., Forrest Research Institute, Dehra Dun, I n d i a n ForrestLeujIet, No. 111 (1947). (70) Nebe, Peter J. (to Carnegie-Illinois Steel Corp.), U. S. Patent 2,485,061 (Oct. 18, 1949). (71) Neukirchen, Joh., Chemical I n g . Tech. 22, 345-7 (1950). (72) Newberg, R. G., Modern Packaging, 23, No. 5, 121 (1950). (73) Nicol, A., Rev. Matdriaux Constr. Trav. Publ., Ed. C. (415), 111-26 (1950). (74) Norman, W. S., Hilliard, A., and Sawyer, C. H. V., Presented a t Conference of SOC.Chem. Ind., Birmingham University (April 18-20,1950). (75) Powers, T. C., Portland Cement Assoc. Res. Lab. Bull., 33 (1949). (76) Preiswerk, E., and Charlton, J., Modern Plastics, 28, No. 3, 85-8 f 1950). \ - - - - ,

(77) Randall, M. C., and Gethen, G. S., U. S. Patent 2,516,342 (July 25, 1950). (78) Reavell, Brian N., Presented a t Conference of SOC.Chem. Ind., Birmingham University (April 18-20, 1950). (79) Reilly, John H. (to Dow Chemical Co.), U. S. Patent 2,523,235 fSeot. 19.1950). (80) Re;nhsrdt, FrankW., and Williams, Harry C., Jr., A S T M Bull. NO.167,60-2 (1950). (81) Reynolds, R. F., Presented a t Conference of SOC. Chem. Ind.. Birmingham University (April 18-20, 1950). (82) Rubin, Louis C., Product Engr., 21, No. 5, 1 3 0 4 (1950). (83) Schaffer, James R. (to B. F. Goodrich Co.), U. S.Patents 2,522,135-6-7-8 (Sept. 12,1950). (84) Schroy, Paul C., Grabrowski, Joseph, and Scott, Milton J. (to American Cyanamid Co.), Ibid., 2,523,333 (Sept. 26, 1950). (85) Schults, Harold W. (to General Motors Corp.), U. S. Patent 2,507,682 (May 16, 1950). (86) Schweizerhall Acid Co., Swiss Patent 265,200 (Feb. 16,1950). (87) Shelburne, T. E., and Sheppe, R. L., Rubber Age ( N . Y . ) , 66, 531-8 (1950). (88) Shepard, Alvin F., and Boiney, J. F. (to Durez Plastics & Chemicals Corp.), U. S.Patent 2,532,374 (Dec. 5, 1950). (89) Silver, I., and Atkinson, H. B., Jr., Modern Plastics, 28, No. 3, 113-114 (1950). (90) Simons, Wm. G,. (to American Cyanamid Co.), U. S. Patent 2,518,388 (Aug. 8, 1950). (91) Squires, Alan T. B. P.(to Rolls-Royce Ltd.), Ibid., 2,523,72930-31-32 (Sept. 26,1950). (92) Thomas, Beaumont, TAPPI, 34, No. 1, 16-20 (1951). (93) Thorvaldson, T., Can. Chem. & Process. Inds., 33, No. 8, 666-70 (1949). (94) Tompkins, Paul C., Biasell, Oscar M., and Watson, Clyde O., IND. ENG.CHEM.,42,1475-81 (1950). (95) Van Gils, G. E., and Clarkson, H., I n d i a Rubber J., 118,773-4, 776 (1950). (96) Vasel, Albert, Sprechsaal, 83, 429-32 (1950). (97) Ward, R., Presented a t Conference of Soc. Chem. Ind., Birmingham University (April 18-20, 1950). (98) Westinghouse Electric Corp., French Patent 942,810 (Feb. 18, 1949). (99) Wiles, Quentin T. (to Shell Development Co.), U. S. Patent 2,528,934 (Nov. 7, 1950). (100) Wiles, Quentin T., and Newey, Herbert A. (to Shell Development Co.), U.S. Patent2,528,932 (Nov. 7, 1950). (101) Wilhelm, Harley A., and Gerald, Park S. (to the United States of America as represented by the United States Atomic ' Energy Comm.), Ibid., 2,521,495 (Sept. 5, 1950). (102) Williams, A. E., Eng. and Boiler House Rev., 65, 314-19 (1950). (103) Wright, James G. E. (to General Electric Co.), U. S. Patent 2,541,851 (Feb. 13,1951). (104) Wyckoff, H. O., and Kennedy, R. J., J . Research XatZ. Bur. Standards, 42,431-5 (1949). (105) Zapater, O., and Llado, Juan, iifinidad, 27, 310-11 (1950). RECEIVED July 19, 1950.