INDUSTRIAL AND ENGINEERING CHEMISTRY
26
also help solve many troublesome problems in industry. An enthusiastic letter was recently received from the superintendent of a zinc smelter who feels they are the answer to a difficult problem a t this plant. Workmen handling zinc sulfate solutions tend to develop sores unless both their persons and their clothes are kept-clean. This is difficult &th soap or other detergents, but simple in the case of a detergent which forms a soluble zinc salt. Many other such special uses will undoubtedly be found as the properties of these materials become better known. The work which resulted in the development of these new detergents has not been limited to any one individual or group, but a few have been outstanding in their contributions. Among these is H. Bertsch, of H. T. Bohme, A.-G., who was the first to point out that the carboxyl group must either be eliminated or “blocked” by other groups in order to achieve hard water insensitivity. Schrauth and his associates of Deutsche Hsdrierwerke A,-G. worked out the methods for making alcohois by catalytic hydrogenation and have
Vol. 26, No. 1
produced these alcohols on a factory scale. The Igepons were worked out and are produced by I. G. Farbenindustrie Akt.-Ges., the great German chemical combine. BIBLIOGRAPHY (1) Anonymous, W o o l Record Textile W o r l d , 40, 1369-70, 1423-5 (1931). (2) Bray, W. W., Am. Dyestuff Beptr., 22, 247-52 (1933). (3) Briscoe, M., J. SOC.Dyers Colourists, 48, 127-31 (1932); 49, 71-3 (1933). (4) Kertess, A. F., Ibid., 48, 7-9 (1932); 49, 69-70 (1933). (5) Killeffer, D. H., ISD. ENG.CHEM.,25, 138 (1933). (6) Lederer, H., Soap, 8, KO.4 , 7 1 - 3 , 7 7 (1932). (7) Lottermoser, A., and Stoll, F., Kolloid-Z., 63, 49-61 (1933). (8) Xusslein, J., J. Soc. Dyers Colourists, 47, 309-12 (1931); Meltiand Textilber.. 13. 27-9 (1932). (9) Schrauth, W., &ifksieder-Ztg.; 58, 61-3 (1931); 2. anoew. Chem., 46, 410, 459-61 (1933). (10) Stadlinger, H., Kunslsedde, 14, 398-404 (1932) ; Melliand Textile Monthlu, 4, 417-20, 499-502 (1933). RECEIVED September 12, 1933.
Modern Developments in Applied Cellulose Chemistry GUSTAVTJSJ. ESSELEN, Gustavus J. Esselen, Inc., Boston, Mass.
M
that time. Even nitrocellulose ODERN developments The cellulose chemical industries may be dilacquers were being used in a i n applied c e l l u l o s e vided into three general classes. The first comvery limited way, but the proper chemistry have been prises those in which the ultimate use of the cellucombination of economic, i n among the most spectacular of lose is as such or in a slightly modified form. d u s t r i a1 , and technical condirecent industrial advances. It This includes paper, three types of rayon, and tions, all of which were necesis a strange coincidence that sary for the establishment of the many of them depend for their the transparent wrapping material Cellophane. modern nitrocellulose lacquer inusefulness largely upon their apThe second class is that in which the ultimate use dustry in a large way, did not peal to the eye. Celluloid, for is in the form of cellulose nitrate. I n this group occur until about ten years ago. example, found wide use as a raw are to be found the pyroxylin plastics (such as Since then, progress along this material from which to manufacce 11uloid, Fiber loid, and Pyral in), photographic line has been rapid. Table I ture toilet articles because of the shows approximately the annual endless variety of combinations film, lacquers, artijicial leather, and cements of production of nitrocellulose lacof color and form into which it various forms. The third class comprises those quers in the United States in could be fabricated with relative products whichjnd their ultimate use in the f o r m certain selected years beginning ease. The appeal of the modern of cellulose acetate. Among these may be cited with 1909, and Table I1 gives a u t o m o b i l e finish is also atthe annual consumption of celluthe cellulose acetate type of synthetic fibers, the tained by means of a cellulose lose nitrate in lacquers during compound, and the attractivetransparent wrapping material Kodapak, the the last seven years. ness of modified cellulose in the safety type of photographicjlm, and new slowIt is sometimes thought that form of Cellophane has revoluburning plastic materials to replace celluloid and thelarge increase in the use of tionized the packaging of prodsimilar pyroxylin plastic products. I n all of cellulose lacquers has been due ucts for domestic consumption. primarily to the rapid growth these groups there is continuing progress and deThe fact that cellulose should of t h e a u t o m o b i l e industry. serve in a large way as a raw velopment. While it is true that large quanmaterial for chemicaI industry tities have been used in this ini s h a r d l y surprising in view of the fact that it isavailable in large quantity in nature dustry, there are other uses far too numerous to list, rangand in forms from which a reasonably pure cellulose can be ing from artificial flowers and artificial legs to window shades separated without undue difficulty. Empirically i t has long and xylophones. That the automobile industry alone is not been used for the manufacture of paper and, during the closing responsible for the remarkable increase in the uses of lacquers quarter of the last century, for making celluloid, but it is only is well illustrated by the fact that in 1927 when the prosince the beginning of the present century that most of the duction of automobiles decreased 23 per cent, the sales of spectacular cellulose products which now attract so much at- lacquers increased 38 per cent. The modern cellulose nitrate lacquer depends for its poputention, made their appearance. larity upon the fact that it dries rapidly to give a hard surCELLULOSE NITRATE face which is very resistant to moisture. Present-day lacThe &st of the cellulose compounds to achieve industrial quers contain, in addition to the cellulose nitrate base, natural importance was the nitrate. By the end of the nineteenth or synthetic gums or both, plasticizers, and sometimes oils. century it was well established as smokeless powder and as together with the necessary coloring materials, the whole the basis of the celluloid industry. The nitrocellulose base being blended with suitable volatile solvents. They are disfor photographic film was also on a firm industrial footing a t tinguished from the earlier nitrocellulose lacquers by the fact
Jaooar>, 193%
1 N D U S T 1%I A 1,
A N D E N G I N E E R I N G C If E M I S T R Y
PULP I ~ - s u ~ n n EQIIIPMENT, xc FnoM TAKE-UP END
that they contain a larger percentage of solids so that fewer coats are required for equivalent coverage. The tendency recently bas been to use somewliat less cellulose nitrate per gallon and more of the synthetic or natural resins. For example, the average amount of cellulose nitrate per gallon of lacquer in 1927 was 1.46 pounds; in 1929 it was 1.25 pounds; and in 1931, 1.22 pounds. TABLE I. AI\-NUAI, h O D U C T I o N OF’ ~ I T I W F B L L U L O S Eh.CQUEBS
the sole and to the bottom of the upper. This is allowed to dry until the two are to be combined, when they are moistened with a solvent “activator” and brought in contact by means of a machine of suitable design. When the process was first started in 1928 it was necessary to hold the soles in contact with the upper under pressure for 30 minutes. By 1931 this time had been reduced to 70 seconds; at the present time under the best operating conditions it is necessary only to hold the sole in contact with the upper for 50 seconds. The 1000 Gallons I000 Gallons process is so rapid that a single operator in 8 hours and 15 1909 1800 1827 1s,s00 1821 1400 IS29 25.000 minutes applied soles to 1580 pairs of shoes. This included 1923 1950 1931 16,400 both the appiication of the solvent activator to the sole and 1925 7300 1932 11.600 TABLE11. ANNUAL CON~UMPT~OX OF CELLULOSE NITRATE the upper, as well as sticking them together. Where two operators work together the average per operator may ND IN LACQUERS even higher. 1000 Povndi IDDO Povnda In the early days the cement was applied with a brush by 1928 8.200 1930 14,000 1827 12.700 1931 13.400 hand, but since then, machines have been developed which 1928 17,300 1932# 8S00 1829 zo.ow apply the cement and also the solvent activator in aocurately * The indieationa ais that 1833 will show s marked increme ovm 1932. measured amounts by means of a finely calibrated mechanical Considerable quantities of cellulose nitrate are also used feed. At the present time 40 per cent of all the women’s in conjunction with textiles to produce coated fabrics (some- shoes produced in the United States are cemented shoes. In times known as artificial leather) which are widely used for 1932 there were required about 100,000 gallons of nitrocelluupholstery, hook binding, and even floor coverings. Box lose cement for this industry, using approximately 168,000 toes for shoes are often made by impregnating canvas or other pounds of nitrocellulose. It is estimated that for 1933 the fabric with a solution of cellulose nitrate in a volatile solvent figures will be approximately double these amounts. During the past year a so-called cold solder has appeared on and permitting the solvent to evaporate. Attractive fancy the market, primarily for domestic use. It consists essencoated papers are now available, made by applying thin coattially of a solution of cellulose nitrate in a volatile solvent, to ings of colored nitrocellulose solutions to paper. For many years cellulose nitrate has been used as an ad- which has been added a considerable proportion of aluminum hesive cement in the manufacture 01 leather belting, and re- powder. cently the same principle bas been extended to the manufacCELLCLOSE ACETATE ture of shoes. This has involved working out a wholly new line of cellulose nitrate adhesives which develop an unusually Although cellulose acetate was known in the laboratory strong bond in a remarkably short time. Although methods long before 1900, its real technical development did not begin operating on this principle had been known previously in until about 1910. Even then its use has lagged far behind Europe, the first production of shoes in this way in the United that ofthe nitrate, onring largely to the fact that i t has always States was in 1928. Table I11 shows the number of shoes been more expensive. At the present time, however, there is produced by this process each year since then. an unusual interest in cellulose acetate as a plastic material to replace celluloid and the other pyroxylin plastics. It has long TABLE 1x1. ANNUALPRODUCTION OF CEMENTED SHOES been known that transparent sheets made with a cellulose Poi,* poi,* acetate bape were much more stable toward light and heat 1928 162.3S8 1931 10.9s4.a2e 1829 2,120,601 1932 20,456,640 than those made with cellulose nitrate. For these reasons 1930 4,560,059 1933(to July 1) 26,215,171 cellulose acetate sheets would be more desirable in the mannThis new method of making shoes entirely eliminates nailing facture of laminated safety glass for automobiles. There or sewing in the application of the sole. It consists in apply- were, however, three reasons why it was not used in the early ing R carefully regulated amount of nitrocellulose adhesive to years of laminated glass manufacture in this country. These
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INDUSTRIAL AND ENGINEERING
were (1) haziness in the sheet, (2) difficulty in developing a satisfactory bond between the plastic and the glass, and (3) higher cost. By means of a series of brilliant chemical achievements these difficulties have all been surmounted so that today it is estimated that more than 60 per cent of all the laminated safety glass produced in this country is made with cellulose acetate as the plastic layer in the “sandwich.”
CHEMISTRY
Vol. 26, No. 1
Cellulose acetate is also finding increasing use in the manufactureof photographic films, particularly for home movies and for x-ray films, an announcement having recently been made that the latter are now being sold at the same price as was formerly charged for the cellulose nitrate films. Cellulose acetate is also available in sheets about 0.001 inch thick as a transparent wrapping and packaging material. I n making both of these products the so-called casting process is used, which consists in first preparing a flowable solution of the c e l l u l o s e ester, together with a certain amount of plasticizer, and permitting this to flow in a carefully regulated stream on t o the highly polished surface of a large metal drum. Arrangements are provided whereby this drum is revolved at a uniform rate of speed in an enclosed chamber in which the atmospheric conditions are carefully regulated and from which the exhaust air is passed through solvent recovery apparatus. It is estimated that in 1931there was in the United States an annual production capacity for the manufacture of cellulose acetate for all p u r p o s e s , i n c l u d i n g synthetic fibers, amounting to about 18 million pounds, although the actual production in that year was only about 15 million pounds. An idea of the rapid rate of increase in the production of cellulose acetate may be obtained from the fact that the indications are that by the end of 1933 Courfesy, Western Electric Co. c e l l u l o s e a c e t a t e will be coming from the factories in this country a t the rate of about .PULPINSULATING EQUIPMENT, FROM FEEDEND 40 million pounds per year. The manufacturers of cellulose acetate succeeded in improvCELLOPHANE ing the solubility of their product to a point where it gave a transparent sheet considerably cleaner and freer from haze Another modern development involving applied cellulose than the standard pyroxylin sheets, and increased production chemistry is the production of thin transparent wrapping tended toward lower costs. The manufacturers of laminated materials from regenerated cellulose. These have found wide glass developed a method of producing a satisfactory bond use under trade names such as Cellophane and Sylphwrap. between plastic and glass. The manufacturer of the trans- The chemistry involved in the manufacture (1) of these thin parent cellulose acetate sheets, by means of a revolutionary filmlike materials is essentially the same as that of viscose process which reduced the time of manufacture from days to rayon and consists in first subjecting cellulose (purified cotton less than the corresponding number of hours, was able to linters or wood pulp) to the action of mercerizing caustic reduce costs to such an extent that the acetate sheets became soda solution. After the excess has been squeezed out, the competitive with those made of pyroxylin. resulting wet cellulose is shredded into a finely divided form Until this new process was developed, the standard method and allowed to age for 2 or 3 days under carefully controlled of making sheets from cellulose acetate or nitrate had con- conditions of temperature. The fluffy cellulosic material is sisted of a succession of time-consuming batch operations, then treated with carbon disulfide which renders it soluble in in many of which, in spite of the strictest precautions, there dilute caustic soda solution. The solution which results is was opportunity for contamination with fine particles of dust. “ripened” under carefully controlled temperature conditions The new procedure, on the other hand, is a continuous one, and at the same time carefully filtered to remove all dirt. and throughout the whole process the material is enclosed It is finally forced through a fine slot into a hardening bath and completely protected from atmospheric contamination which is ordinarily composed of an aqueous solution of sulfuric and dirt. The cellulose ester is converted into a continuous acid and sulfates. This regenerates the cellulose from its sheet or web which passes through a continuous drier where soluble compound and converts it into a continuous thin ribit loses its solvent and emerges at the end in the form of a bon. The ribbon is passed through successive washing and continuous, seasoned sheet. It is then rolled into large rolls, purifying baths, followed by a glycerol solution, and is finally either the full width of the machine or slit according to the dried. particular demands at the moment. I n a modification of this process, the cellulosic solution I n addition t o the marked savings in time and labor, one after the final ripening is forced through a circular slot into of the striking advantages offered by the new process is the a salt hardening bath to form a continuous tube which, after improvement in quality which has resulted. Whereas for the necessary washing, purifying, and softening steps, is the material produced in the old way a strict inspection and used in the manufacture of sausage casings. I n this congrading of the product was required, practically all of the nection it is interesting to note that sausage made in this material produced by the new process is of first quality and way often has the casing stripped off before it is marketed. These transparent wrapping materials of regenerated celluit is at the present time being shipped in continuous rolls of different widths up to 2000 feet in length. The new process, lose are sensitive to changes in atmospheric humidity condiwhich was developed at theFiberloid Corporation, is applicable tions and permeable to moisture. For this reason they d o to both pyroxylin and cellulose acetate sheet materials. and not afford a satisfactory degree of protection either to naturally moist products or t o those which should be protected bids fair to mark a new era in this industry.
January, 1934
I N D U S T R I A L .4 I\; D E N G I N E E R I N G C H E M I S T R Y
from moisture. T o overcome this defect, a process has been developed for applying a very thin surface coating which renders the material more resistant to moisture.
29
from it is reflected specularly. Although rayon filaments are normally transparent, a certain proportion of the light is reflected each time it meets the surface of a filament, so that, a s the light passes down through a bundle of filaments, each filament causes some of the light to be reflected until finally practically complete reflection results. The introduction into t h e fibers of a small amount of finely divided material, with an index of refraction different from that of the rayon substance, accomplishes two things: It tends to reduce the amount of light which is reflected specularly and a t the same time causes some of the light to be reflected diffusely. Both of these factors increase the proportion of diffuse reflection and accordingly give a more or less delustered appearance, depending upon the extent to which the effect is carried. Another interesting trend which has received unusual impetus during the past year is the marked increase in the production of synthetic fibers from cellulose acetate. The amounts of cellulose acetate rayon produced in the United States in recent years is as follows:
SYNTHETIC FIBERS There are several recent developments of note in the synthetic fiber or rayon industry. For a number of years the tendency has been to increase the number of filaments in rayon threads of a given size or, in other words, to decrease the size of the individual filaments. For example, in the early days of the rayon industry in this country it was common to have 150 denier rayon with sixteen individual filaments. Kowadays it is not uncommon to have sixty filaments in a thread of the same size. I n fact, synthetic fibers have been made with individual filaments as small as one denier, but, as the size of the filaments becomes too small, there is an undue tendency to break or “catch,” thus producing a fuzzy fabric, particularly after it has been used a short time. Perhaps the outstanding recent development is the change 1000 Pounds 1000 Pounda during the last few years in the public demand from materials 1928 5,000 1931 15,000 1929 7,500 1932 13,60Q with high luster to fibers with a subdued sheen. This has 1930 9,000 reached such proportions that estimation shoms 70 per cent of the synthetic fibers produced in this country today to have This increase has been due in large part to improvements in a more or less delustered finish. The normal method of reduc- manufacture of cellulose acetate which have resulted in ing the luster of a material is, of course, to roughen its surface. lower costs of production. I n the case of rayon, however, such a method would have the Several years ago considerable interest was aroused among disadvantage of imparting an unpleasant feel to fabrics made the manufacturers of viscose rayon by a process which claimed of such fibers and also of leaving them open to the possibility to produce rayon which was stronger than natural silk when that, if the result were accomplished by a surface application dry and a t least as strong as natural silk when wet. Careful of some finely divided substance, this substance might be investigation showed, however, that, while it was possible slowly removed by wear. to obtain this strength as claimed, nevertheless it could be I n the case of transparent substances such as rayon fibers, accomplished only a t a higher cost for chemicals; furtherthere is a second and more suitable method of reducing the more the resulting fibers had a marked tendency toward luster which consists in introducing relatively small propor- brittleness, which prevented their use for most practical tions of suitable finely divided substances inside the fiber it- purposes. I n view of this, it is not surprising that the process self. This can be done with proportions so s~nallthat they has not assumed commercial importance. do not affect the smoothness of the surface. The substances may be either solid or liquid, the essential characteristic PCLP-INSULATED WIRE being that they should have an index of refravtion different A rather unique use of wood pulp is in the manufacture of from that of the rayon. The principle upon which this method of delustering de- fine sizes of insulated electric wire in which the insulation is pends is entirely different from that used in making a “flat” supplied by a layer of wood pulp which is formed directly on or “matte” surface lacquer. I n general, the extent to which the wire by a modified paper-making process. I n the early a surface is delustered ( 3 ) depends upon the proportion of days, when paper was first used as an electrical insulating malieht .. which is reflected from that surface in a diffuse or scat- terial, it was felt that only papers made from Manila or hemp tered manner as compared with fibers were suitable for this m r the total amount of reflected pose. Further studies shoGed, light, part of which is reflected however, that it was entirely specularly and part diffusely. f e a s i b l e t o u s e wood pulp I n m a k i n g a lacquer which papers, provided proper predrieswith a dull surface, enough cautions had been taken in pigment is ordinarily employed preparation of the pulp. I n deso that its bulk produces a scribing a unique process Little rough surface when the lacquer (9)says : “Paper is made on a dries. This roughened surface 36-inch face single-cylinder wet causes light falling on it to be machine in the usual way. Inreflected diffusely, as compared stead of making a single web, with the specular reflection of however, the mold is deckled light from the more or less glassoff with paint deckles so that it like surface of an unpigmented f o r m s s i x t y small 0.25-inch lacquer. With rayon, on the webs. The wire to be insulated other hand, it is posrible to prois run around the mold at the duce a delustered yarn without same time the sheet is formed. affecting the smoothness of the In this way the wire is emsurface of the individual filabedded in the wet pulp ribbon ments. The luster of rayon deas it leaves the mold and all C o u r t e s y , United Shoe M a c h i n e r y C a r p . pends upon the fact that practhat is required from then on is tically all of the light reflected to press out the water, wrap the C E h l E N T SOLE A T T 4 C T “ G hf.4CHInT ( ~ ~ O D E B) L
30
INDUSTRIAL
AND ENGINEERING
ribbon around the wire, dry the insulation, and reel up the finished product.” This process is now supplying a large percentage of the fine-gage insulated wire for telephone cable work. It is expected that a little later it will be possible to apply this type of insulation to larger gage cables and for circuits other than those in the telephone industry.
PAPER AND RUBBER There is another interesting development which has been making progress quietly during recent years and which gives promise of developing into a specialized industry. It involves integral combinations of paper with rubber, the rubber usually being in the form of latex. There are two general processes for making these products. One involves mixing the latex with pulp in the beater, while in the other the paper or board is made first and saturated with rubber latex afterward. The various products made in this way are finding increasing use in the manufacture of shoes, particularly as inner soles and midsoles; in the automobile industry as rim strips, body shims, washers, etc.; and as a base for pyroxylin coatings in the manufacture of imitation leather. LATESTDEVELOPMENTS During the last ten years there has been considerable reference in the patent literature to the subject of cellulose ethers, and, during the past year or two, materials which belong in this chemical classification have made their appearance on the market in a limited way. The simplest ether of cellulose is the methyl ether. It can be made water-soluble and is being offered under several trade names in connection with textile h i s h i n g and printing operations. Considerable study has also been devoted to ethyl cellulose, and this also is available on the market for special purposes. Perhaps the most promising of the cellulose ethers a t the present time is the benzyl, which is being manufactured in Europe and can be purchased in this country. It is reported that a t least one American manufacturer is studying the feasibility of producing this ether here. Benzyl cellulose is unusually stable toward chemical action. It is not decomposed by alkalies of mercerizing strength, nor
CHEMISTRY
Vol. 26, No. 1
is it affected by sulfuric acid up to 50 per cent concentration. Furthermore, benzyl cellulose is unusually resistant to water and moisture. It is claimed that films made of benzyl cellulose are practically impermeable to water vapor. It will probably be necessary to improve somewhat on the methods of production which have so far been published, but with benzyl chloride available a t low cost, it is reasonable to expect that benzyl cellulose will be available in the near future a t moderate prices for such purposes as thin transparent wrapping materials, electrical insulation, lacquers, and industrial finishes, molding powders, and for conversion into the innumerable articles which are now fabricated from pyroxylin plastics. There is also, a t the present time, considerable interest in mixed cellulose esters in which the hydroxyl groups instead of being all esterified by the same acid, are esterified partly by one acid and partly by another. It is claimed, for example, that cellulose acetopropionate offers several advantages over any of the cellulosic compounds which are now available. With relatively inexpensive propionic acid promised by the organic chemical manufacturer, it seems probable that in the near future cellulose acetopropionate also will be available for the many purposes for which cellulose compounds are now being used. Moreover, all of these latest cellulose compounds are to be regarded only incidentally as replacing cellulosic or other materials which have been available for a longer time. Their chief importance lies in the probability that their novel properties will greatly extend their use.
ACKNOWLEDGMEXT The information and figures given in Table I11 regarding cemented shoes were furnished through the courtesy of the United Shoe Machinery Corporation and its subsidiary, the Boston Blacking and Chemical Corporation. LITERATURE CITED (1) Hyden, W. L.,IND.EKQ.CHEM.,21, 405 (1929). (2) Little, J. S., Tech. Assoc. Papers, Series 16, No. 1. 150 (1933). (3) Pfund, A. H . , J. Optical SOC.Am., 30. 23 (1930). RECEIVED September 8, 1933.
~
The Synthetic Rubber Problem’ WALLACE H. CAROTHERS, E. I. du Pont de Nemours & Company, Wilmington, Del. This paper is a n attempt to indicate the nature If this were true it should be WO o b j e c t i v e s i n atand current status of the synthetic rubber problem possible to infer the structure tempts to s y n t h e s i z e by a study of chemical behavior r u b b e r are (l) to disfrom the standpoint of organic chemistry. I t and then to make a r a t i o n a l cover or demonstrate completely includes a n outline of unsolved problems and synthesis-that is, from known the structure of rubber and exsome new data bearing on the relation between starting materials to build up plain its properties in terms of the structure of dienes and their suitability as by known and d e l i b e r a t e l y this structure, and (2) to procontrolled steps the supposed duce artificially a commercially starling materials f o r the synthesis of rubber. acceutable s u b s t i t u t e . The structure. If the synthetic product was then exactly identical second of these objectives is now an accomplished fact, but the first is far from having been in all its properties with the natural product, the structure of the latter would be proved. achieved. What is sometimes referred to as the synthesis of rubber The difficulties in this connection can be illustrated by first viewing the facts in the light of the assumption that consists essentially in this: Isoprene on standing passes rubber hydrocarbon is a chemical individual in the usual slowly into an elastic solid having the chemical composition s e n s e i . e., that it is made up of identically similar molecules and many of the chemical reactions of rubber. But alcapable of being represented by a single definite formula. though this material is elastic, it is not physically identical with rubber; few experts in the field would mistake it for 1 Because of the oomprehensive historical article on “Synthetic Rubber” rubber. The product synthesized, then, is probably not publiahed by Whitby and Kats [IND.ENQ.CEBM.,25, 2105. 1338 (1933)l rubber; and, even if it were, the synthesis is not rational. since thia paper wae preaented in Chicago, it has been considerably revised It is a spontaneous or accidental transformation of unknown with the elimination of historical matter.
T
