BIOLOGICAL CHEMISTRY
BIOLOGICAL CHEMISTRY
Pure Riboflavin-5-Phosphate Synthesized on Large Scale • Researchers outline the application of tonography to the study of amino acids and proteins • Information concerning amounts of folic acidlike compounds in human blood may aid cancer detection • Continuous-flow recording spectrophotometer useful in separation of nucleic acid derivatives
C. F. Hiskey explains curve used in proving theory of absorption law deviations in relative transmittance measurements Precision Colorimetry. T w o timely problems involving precision colorimetry and absorption law deviations in relative transmittance measurements were discussed by C. F. Hiskey, Polytechnic Institute of Brooklyn. This system of analysis employs a high absorbance solution as reference standard. Dr. Hiskey described a method used with single-component systems, which produces an analytical precision more than ten times that obtained in absolute colorimetry. T h i s method consists of setting the instrument with the standard in place so that a reading of 1 0 0 % transmittance is obtained. T h e unknown of slightly higher absorbance than the reference standard is then substituted and the concentration difference determined. For two-component systems, an absorptivity coefficients ratio must be introduced into the usual set of two equations which describe s u c h a system. A precision of one part per thousand is achieved by this method, which produces a substantial increase over colorimetric methods used in such systems as permanganate-chromate. Gas C o n t a m i n a n t s . T h e heat of catalytic conversion forms the basis for continuous assaying and recording of low concentrations of contaminants in gases, related G. Cohn, Baker and Co. Gas mixtures are prepared containing known amounts of the constituent to be determined, a n d these mixtures are passed over small catalytic reactors of known conversion factors. T h e resulting gas is used for calibration purposes because of the difficulty of preparing flowing gas mixtures. Dr. C o h n pointed out the applicability of the method t o trace analysis of industrially important gases, such as oxygen or hydrogen in gases and carbon monoxide and dioxide in hydrogen and hydrogen-containing gases.
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n p i i E large-scale synthesis of riboflavin•*- 5'-phosphate was announced by Leo A. Flexser and Walter G. Farkas of Hoffmann-La Roche. They found that riboflavin can b e readily phosphorylated in good yield b y treatment with a chlorophosphoric acid, which may b e prepared by the reaction of phosphorus oxychloride with one or t w o moles of water or with phosphoric acid. Chlorophosphoric acids, although previously almost unrecognized, are particularly useful reagents for phosphorylating sensitive substances with minimum destruction, the authors said. These acids have t h e further advantages that no base such as pyridine is needed to effect the reaction (as is the case with phosphorus oxychloride); rigidly anhydrous conditions need not b e maintained during the reaction; they are good solvents; and the isolation of the product is easily accomplished. T h e reaction of these acids with riboflavin is rapid at ordinary temperatures, hydrochloric acid being evolved and a homogeneous solution obtained. Upon the addition of ether to the resultant solution, a yellow precipitate is formed which is probably, in the main, a chlorophosphoric acid salt of the cyclic riboflavin-4%5'-phosphate. Upon hydrolysis, the cyclicphosphate ring opens mainly at the 4' position, giving a good yield of riboflavin5'-phosphate in a fair state of purity. Further purification is brought about by the recrystallization of the monodiethanolamine salt. T h e final product was found to be fully active biologically and enzymatically. Its chromatographic behavior and distribution coefficient were identical with the natural riboflavin-5'-phosphate (flavin mononucleotide). The report indicated that this is the first preparation of this biologically important substance in pure form in quantities greater than milligrams. . The subsequent paper by E . De Ritter, J. Scheiner, F . W. J alms, L. Drekter, and S. H. Rubin, also of Hoffmann-La Roche, indicated that the riboflavin activity of synthetic riboflavin-5'-phosphate and its monosodium and monodiethanolamine salts had been determined by fluorometric,
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microbiological, and rat giowth methods and in human availability tests. Pure preparations were found to be fully as active as riboflavin on a molar basis for Lactobacillus casei, as well as b y direct fluorometric assay. However, the microbiological response is the better criterion of purity since closely related compounds may have full fluorescence but lesser b i o logical potency. Comparative urinary excretions after oral dosage of riboflavin, riboflavin-5'-phosphate, or its monodiethanolamine salt indicate that both of the latter are completely available to humans. Fluorescence measurements after extraction of these urines with benzyl alcohol provide evidence that riboflavin-5'-phosphate and its salt are excreted largely, if not entirely, as free riboflavin by h u man subjects.
• Amino Acids and Proteins The application of ionography to the study of amino acids and proteins w a s discussed in the paper by H. J. McDonald, M. C. Urbin, and M. B. Williamson of the Loyola University School of Medicine. In the technique described, an electrical potential is applied across the ends of a filter paper ribbon, saturated with a buffer solution, to which has been added a microquantity of the substance under study. T h e ribbon is suspended horizontally in a helium atmosphere. T h e mobility of the substance under the unidirectional electric field is measured in buffers of constant ionic strength but varying p H . A plot of jnobility against pH change is then made. T h e point where the curve crosses the zero mobility axis corresponds to the isoelectric point of the migrant. Isoelectric points obtained by this method are in excellent agreement with values obtained by classical methods. Some of the isoelectric points as determined by ionography were 7.6 for histidine, 3.1 for glutamic acid, 4.8 for bovine serum albumin, and 4.7 for casein. The electromigration velocity of the substances studied w a s not affected by either adsorption on the filter paper ribbon or by electro-osmosis. It was pointed out that the
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INTERNATIONAL CONGRESS
Gerrit Toennies and coworkers Henry Frank (left) and Dorothy Gallant, Institute for Cancer Research, inspect blood dialysates obtained in investigation o f folic acid activity of human blood mobility of bovine serum albumin, as determined by ionography, is the same as that determined by the moving boundary method. Adsorption Chromatography. In their paper on the separation of 16 dinitrophenylam'no acids by adsorption chromatography on silicic acid-Celite, F. Charlotte Green and Lois M. Kay of CalTech reported th:vt Sanger's method for the determination of the free amino groups in proteins by the use of 2,4-dinitrofluorobenzene has proved extremely useful in the study of numerous protein substances. However, his technique for the separation and identification of the bright yellow 2,4-dinitrophenyl derivatives of the more common acids by "partition" chromatography requires considerable time for a complete analysis. Moreover, the behavior of the derivatives varies considerably from one batch of silica gel t o another. A more rapid systematic method has been devised by the CalTech scientists for the qualitative separation and identification of various ether-soluble 2,4-dinitrophenylamino acids b y "adsorption" chromatography on silicic acid-Celite. In this method, a chromatographic tube is packed under suction w i t h a dry mixture of silicic acid and the filter aid, Celite. The resulting column is prewashed to remove the "free" water from the adsorbent before the sample is placed o n the column for development. Some acid such as formic or acetic is necessary in the developing solutions in order to obtain satisfactory movement of the zones. The developing solvents which are used in this method contain oni- of these acids and acetone or ethyl acetate in petroleum ether, cyclohexane, or benzene. This technique is said to require about one third to one fourth as much time as the "partition" method. Glyconyl Peptides. A . new class of carbohydrate amino acids which might be of biochemical interest has been synthesized by David G. Doherty of Oak Ridge National Laboratory. T h e s e are
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Hugh J. McDonald and Martin B. Williamson of Loyola "University observe the results of an ionographic separation of proteins. Their findings were reported to the Biological Chemistry Section
aldonic acids coupled through their carboxyl group in a stable CO—NH 2 linkage to the amino group of amino acids. The name glyconyl peptide is proposed for this type of compound, as its major difference from a peptide is the replacement ol the NH 2 group in an alpha position to the peptide linkage by a bydroxyl group. These compounds are prepared by coupling the acetylated aldonyl chloride with a free amino acid ethyl ester to give an excellent yield of acetylated aldonyl amino acid ester. This compound can be catalytically deacetylated to yield the aldonyl amino acid ester and either deesterified to the free aldonyl amino acid or converted to the amide with methanolic ammonia. Heats of Hydrolysis. Alan Dobry and Julian M. Sturtevant of Yale University have applied their recently developed calorimetric method to the direct evaluation of the heats of enzyme-catalyzed hydrolyses of peptides in dilute aqueous solution at approximately neutral pH. The hydrolysis of the peptide bond in carbobenzoxyglycyl-L-phenylalanine b y carboxypeptidase has been found to liberate 1800 calories per mole, while t h e hydrolysis of the amide bond in benzoyl-L-tyrosinamide by chymotrypsin liberates 5100 calories per mole, both reactions taking place in solutions of ionic strength 0.3 (added salt) at 25° G. Electrophoresis. In their report on the electrophoresis of proteins and smallmolecule electrolytes, W. W. Davis, T. V. Parke, and R. Gamewell of Lilly Research Laboratories indicated that two systems of electrophoresis were employed which involved the use of agar-filled glass capillaries of approximately 1.5-mm. internal diameter and 7.5-mm. external diameter. The special feature of these systems is a very sharp initial boundary at the end of a capillary which permits resolution of component boundaries within a distance of approximately 1 cm. The use of a gel makes it possible for voltages above 10 volts per cm. to be em-
CHEMICAL
ployed without convection difficulties. Separation can be completed in less than 15 minutes. The capillary does not require thermostating, and the apparatus is relatively simple. In the first system applicable t o proteins, samples of the order of 5.0 m g . of protein can be separated. This corresponds to approximately one drop of serum. An optical reading device permits the recording of complete curves in about five minutes. In the second system, applicable to small-molecule electrolytes, an initially thin ( approximately 0.2-mm. ) layer of sample is developed by electrophoresis into an agar column in a glass capillary. After development, the s u b stances are distributed in zones a s in a chromatographic column. The column of agar is extruded and cut into approximately 0.5-mm. sections and the successive sections are examined for their c o n tents of separate substances present in the sample. Contractile Protein of Muscle. T h e purpose of the investigation reported b y W. F. H. M. Mommaerts and Robert G. Parrish of Duke University was to study in pure systems the molecular interactions which constitute muscular contrnction, in order to arrive at a detailed understanding of the mechanism involved. As far as is known, the substances involved in contraction are myosin, actin, adenosine triphosphate, and inorganic ions. Since contraction is a rearrangement in molecular dimensions of muscular matter, a major portion of the investigation was concerned with the determination of the mokcular sizes and shapes of these protems and with the dynamic aspects of their interactions. Myosin, as now available, is considered to be a pure substance, as judged from its behavior in electrophoresis, ultracentrifugation, and . the phase-rule solubility test. Its molecular dimensions have been calculated from measurements of light scattering and other physical properties. Actin has been purified by reversible
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ENGINEERING
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BIOLOGICAL CHEMISTRY polymerization and ultracentrifugal isola tion of the polymerizate. In the absence of salt, the globulin protein settles as a single component showing boundary sharpening due to the sedimentation po tential. Upon the addition of salt, the protein polymerizes to fibrous actin, and the completeness of this transformation is further proof of the purity of this protein. At alkaline reaction, the protein polymer izes in only one manner, presumably by strictly longitudinal aggregation.
• Folic Acid-Like Compounds in Blood The amount of folic acid in the blood may be related to the presence or absence of cancer in the body, according to a re port by Gerrit Toennies, Henry G. Frank, and Dorothy L. Gallant of the Institute for Cancer Research, Philadelphia. Fast-grow ing tissues, such as cancer, may require more of the vitamin than normal tissues. Encouraging results have been obtained in the experimental treatment of certain forms of cancer by the injection of folic acid antimetabolites. These compounds closely resemble folic acid in chemical structure and can therefore enter into some of the reactions of the true vitamin. How ever, because of differences in some im portant structural details, the antimetab olites cannot follow through on the reac tion path of the vitamin, and, as a result they prevent the utilization of folic acid. The report stressed the fact that there is actually no free folic acid in the blood; what the experimenters measured was some other compound or compounds re sembling folic acid. Whatever this factor is, it appears to be present in blood in an amount 30 to 50 times as great as had been accepted for folic acid in the past. If the normal level of the folic acid factor in the blood can be established, the authors pointed out, any marked drop
below this level might be traced to a can cerous growth. D. I. Weisblat and coworkers at Upjohn reported a new synthesis of folic acid. In this process, 2,4,5-triamino-6-hydroxypyrimidine is reacted with an IV-alkylated p-aminobenzoylglutamic acid. Labile Methyl Groups. The utilization of formate in the formation of labile methyl groups has been further investigated with C u -deuterioformate, according to a paper by Charlotte Ressler, Julian R. Rachele, and Vincent du Vigneaud of the Cornell University Medical College. Studies had previously been undertaken with the use of methanol doubly labeled in its methyl group with C14 and deuterium in an in vivo experiment in the rat, in an effort to determine the possible pathway by which the carbon of methanol arrived in the labile methyl group. Approximately one hydrogen was found to accompany each carbon of the methanol into the newly synthesized methyl group which made its appearance in choline. Sodium C 14 -deuterioformate was ad ministered subcutaneously to the rat and guinea pig. The choline was subsequently isolated from the tissues and degraded to trimethylamine, which was isolated as the chloroplatinate. The comparison of the ratios of deuterium to C u in the ad ministered formate and in the trimethyl amine indicated that formate entered the methyl group of tissue choline with no detectable loss of its hydrogen. It is thus clear that in the conversion of formate into a labile methyl group, such inter mediates as carbon dioxide, cyanide, isocyanate, or such others possessing either no hydrogen atom or readily exchangeable hydrogen atoms are precluded. Any hy pothesis concerning the conversion of formate to the labile methyl group must envisage no labilization and no loss of the hydrogen attached to the carbon, the paper stated.
M. S. Dunn ( s e a t e d ) , University of California at Los Angeles, and graduate students Richard Zuckerman and Alfred Deutsch inspect their results from automatic recording ultraviolet spectrophotometer. Application of this instrument to separation of nucleic acid derivatives was discussed in their paper before the Biological Chemistry Section
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Fa* Absorption. The fat absorption in the rat was studied with C 14 -labeled stearic, palmitic, and butyric acids, ac cording to a report by Sune Bergstrom, Bengt Borgstrom, and Max Rottenberg, of Lund, Sweden. The acids were fed by stomach tube as the free acids dis solved in an inactive glyceride and incor porated into a glyceride by transesterification. The rate of absorption and the dis tribution of the absorbed material in dif» lerent organs was followed up to 48 hours. The glycerides, cholesterol esters, and the different phospholipides were separated according to a modification of the usual fractionation procedure. The activity of the fatty acids in these different groups of compounds was followed in intestinal mucose, plasma, liver, fat, and elsewhere.
ί» Nucleic Acids "A Continuous-Flow Recording Ultra violet Spectrophotometer and Its Applica tion to the Separation of Nucleic Acid Derivatives" was the title of a paper by Alfred Deutsch, Richard Zuckerman, and Max S. Dunn of the University of Cali fornia at Los Angeles. According to their experimental procedure, the eluate of a chromatographic column is passed through a Beckman spectrophotometer and then through a device which measures the vol ume throughput. A servomechanism changes the wave length setting of the spectrophotometer, alternately selecting four predetermined wave lengths in rapid succession. The percentage transmission of the sample stream at each of the four wave lengths is plotted by a multipoint recorder, synchronously with the record of volume throughput. From these curves, the nature and amount of each constituent are readily determined. On the other hand, for preparative work, the eluate after passage through the spectrophotometer is directed to a mani fold of electrically operated valves actu ated by a switch on the recorder. In this manner, fractions are collected, each frac tion representing a complete optical den sity peak—that is, all of one component. Test mixtures of adenine, guanine, cytosine, uracil, thymine, and mixtures of the nucleotides of the first four compounds were resolved. In this manner, all these compounds were also purified in gram quantities for use as standards. Thymonucleic Acid. In experiments on the free diffusion of dilute thymonucleic acid solutions into water and aqueous salt solutions, an anomalous behavior was noted by J. A. V. Butler, D. W. F. James, and Β. Ε. Conway of the Royal Cancer Hospital in London. The boundary, in stead of becoming progressively more diffuse, continued to have a sharp front which advanced into the solvent, the dis tance covered being proportional to the square root of the time. The proposed explanation for this behavior is that the nucleic acid possesses a gel structure even in dilute aqueous solutions, which pre vents the free diffusion of the molecules
3949
INTERNATIONAL CONGRESS in the advancing front. T h e diffusion is, therefore, really a swelling process of the dilute gel. The effect of chemical agents such as the nitrogen mustard C H 3 N ( C H 2 C H 2 C l j a is to destroy the viscous nature of the solutions, giving a comparatively "normal" solution. This action is caused by the csterification or alkylation of the groups which are responsible for the formation of intermolecular hydrogen bonds. The result of such action is to break down the gel into its component molecules, which are chemically modified. T h e molecular weights obtained in such a solution are considered to be more representative of the nucleic acid molecule than those deter mined widi the original associated solu tions. Molecular weights between 104 and 10 5 have been obtained, depending on the nature of the treatment. Fneumococcus Type VI. T h e prepara tion of the desoxyribonucleic acid through the previous isolation of the desoxyribomicleoprotein in fairly pure form has been accomplished by Virgil L. Koenig, Louise Larkins, and J. D . Perrings of the Los Alamos Scientific Laboratory. The solu bility properties of the desoxyribonucleoprotein from the pneumococcus Type VI are different from the solubility properties ot t h e desoxyribonucleoprotein isolated Irom calf thymus. The nucleoprotein pos sesses the ability to transform rough pneumococcus organisms into smooth or ganisms under proper conditions of cul ture technique. The conversion of weighed amounts of the nucleoprotein into the nucleic acid makes it possible to ascertain roughly the amount of pro tein combined with the nucleic acid to form the nucleoprotein. Ascorbic Acid Oxidation. After num erous negative experiments o n the possible effect of thyroxine on oxidations in animal
tissue slices and homogenates, Chalmers L. Gemmill of the University of Virginia Medical School conducted tests on the effect of this hormone on vegetable oxi dases. It was found that small amounts of thyroxine stimulated the oxygen uptake of the ascorbic acid oxidase system. The purified preparation of ascorbic acid oxi dase was obtained from squash. However, thyroxine had no effect on the oxidation of catechol by tyrosinase. Since ascorbic acid oxidase is a copper protein, the effect of thyroxine was studied on the topper-induced oxidation of ascorbic acid. Later, attention was directed toward a possible effect of thyroxine on cytochrome oxidase in the system ascorbic acid—cyto chrome—rat 1 °art homogenate. N o effect was observed with heart homogenate preparations from normal, thyroid-ectomized, or thiouracil-trealed animals. A slight inhibition of oxidation of this sys tem was observed when dried thyroid gland was used with heart homogenates from normal animals. Greater inhibition was found "when the heart homogenates were prepared from thiouracil-treated animals. Hyperglycemic Factor. A transient hy perglycemia is produced in animals and man on intravenous injection of various commercial insulin preparations. A study of the separation of this hyperglycemic factor from the urine of alloxan-diabetic rats and rabbits and diabetic man was reported in the'paper by M. Osman Saka of the University of Istanbul, Turkey. Under the action of alloxan, the insulincontaining beta cells of the pancreas are destroyed and the alpha cells remain in tact. It is supposed that the hypergly cemic and glycogenolytic factor is pro duced by the latter cells. In the case of alloxan-diabetic animals, as well as in diabetic man, the substance which is
E. I. Valko, Brooklyn Polytechnic Institute, with Κ. Η. Meyer, University of Geneva, Switzerland, who discussed the behavior of elastomers at small torsions. Right. Mrs. Ruth Stookey
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supposedly produced b y alpha cells should be detected in blood and urine. A n at tempt was made to separate this factor from the urine of alloxan-diabetic rats and rabbits by fractional alcoholic pre cipitation at various pH. A precipitate was obtained with 7 0 % alcohol. T h e in travenous injection of this precipitate (dis solved in an 0.85% solution of sodium chloride at p H 4.5) produced a marked hyperglycemia in a normal rabbit. Pyridoxal Phosphate. Andrew N. Wil son and Stanton A. Harris of Merck an nounced that an improved synthesis of pyridoxal phosphate ( codecarboxylase ) has been attained by the phosphorylation of pyridoxamine with phosphorus pentoxide in sirupy phosphoric acid. The inter mediate, pyridoxamine phosphate, is read ily oxidized to pyridoxal phosphate, either spontaneously in the presence of charcoal or b y oxidizing agents such as manganese dioxide. The resulting pyridoxal phos phate is absorbed from acid solution by charcoal, which allows the separation of ail inorganic acids and solutions. The py ridoxal phosphate is then eluted with an alkaline solution or, preferably, an am monium hydroxide solution. The crude ammonium pyridoxal phosphate obtained by evaporation gives a yield of better than 5 0 % of the codecarboxylase oxime. The coenzyme activity indicates that the product may b e as high as 80% pure. However, pure pyridoxal phosphate has not yet been obtained. Labeled Glycerol. Last year, Hermann Schlenk and Bernice Wallace D e H a a s of the Texas Agricultural Experiment Sta tion reported a method for the synthesis of C w -labeled glycerol in which nitromethane and radioactive paraformalde hyde served as the starting materials. The relatively low yield of 1 9 % has been at tributed partly to the quality of the mate-
and S. D . Stookey, Corning Glass Works, show the new forms of photosensitive glass during session on glass and proteins before Section on Elastomers and Plastomers
CHEMICAL
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ENGINEERING
NEWS
ELASTOMERS A N D PLASTOMERS rials (the degree of polymerization of the radioactive paraformaldehyde) and partly to the numerous intermediate steps caus ing considerable loss of material. A different method has since been de veloped, starting with chloroacetyl chlo ride, which gives better yields. The quality
of chloroacetyl chloride is easier to control than that of paraformaldehyde. Chloro acetyl chloride may be labeled in the carboxyl group or in the methyl group, producing β- or α-labeled glycerol, re spectively. Pure glycerol is given in a yield of 38°/o based on chloroacetyl chloride.
ELASTOMERS A N D PLASTOMERS
N e w Photosensitive Glass Leads To Improved Chemical Engraving • •
Polymer carbon promises improved service
Knowledge rubber advanced
of
A PHOTOSENSITIVE silicate glass in which -**· operations such as drilling, cutting en graving, and sand-blasting can be replaced by a solution process was described by S. D . Stookey, Corning Glass Works. The selectivity of the solution process is made possible by a photochemical reaction. T h e method reported by Dr. Stookey consists of forming in the glass a threedimensional photographic image, then dis solving it with hydrofluoric acid. In this process the exposed sections, after devel opment, dissolve at about 23 times the rate of the unexposed glass. The glass is made photosensitive by the presence of trace quantities of gold, silver, or copper, with sensitizers. In the photographic proc ess, metallic particles are precipitated in the glass by successive treatment with actinic light and heat. On further treat ment the particles induce crystallization, nucleating crystals o f some of the major constituents of the glass. The resulting devitrified regions contain soluble crystals such as lithium silicate and are readily penetrated by hydrofluoric acid; adjacent vitreous regions are attacked very slowly in comparison. One of the advantages of the new process cited b y Dr. Stookey is that no protective coating is needed. Detailed de signs can b e accurately processed on mass production scale, it was declared, yet pieces can be produced with designs so intricate that their mechanical manufac ture would be impractical. T h e process can b e applied in drilling multiple holes of complex shape and precise dimensions, in cutting out small or irregular shapes, and in photoengraving.
mechanism
of
polyacrylic
polymers, was the subject of a paper by W. O. Baker and F. H. Winslow, Bell Telephone Laboratories. The nature of this product makes it significant technically for electrical, mechanical, and chemical uses of a hard, refractory, electron-microscopically smooth, geometrically regular form of carbon, it was declared. According to Dr. Baker, polymers such as polydivinylbenzene and polyvinylacetylene can be progressively dehydrogenated in an inert atmosphere with enough of the original bond network surviving the heat treatment at temperatures u p to 1200° C. to retain the original gross form. With original cross sections greater than 2 mm., it was stated, pieces of polymer carbon may b e cracked. A unit volume of original polymer, for
example, a small sphere, goes down to an over-all volume of 0 . 4 7 8 cc., after con version to polymer carbon at 960° O , without changing shape. During this change it loses 5 2 % of its weight and its absolute density increases from 1.05 to 2.05. The true volume of carbon in this product is about 2 5 cc. and the pore vol ume is about 2 3 cc. or 4 8 % of the final space in the carbon sphere. T h e empty space relates roughly t o the amount of volatilized material; the atomic rearrange ment shrinks the total sphere size down in proportion to the increase in atomic density; the specific volume of matter decreases by 4 8 % while the apparent vol ume, judged by diameter in the case of a sphere, shrinks by 5 2 % . This would not be expected with the formation of discrete graphite crystallites. T h e x-ray scattering o f polymer carbon suggests cross-linked graphitic layers, re ported Dr. Baker, leading to diamondlike hardness. Reordering, o r true graphitization, does not occur at 2 4 0 0 ° C , he pointed out. Partially dehydrogenated de rivatives form a series of organic electronicsemiconductors. With about 2 3 carbon atoms per hydrogen atom, specific resis tivity at 2 5 ° C . is 1 χ 10"2 o h m cm. Ab sorption spectra show that the electrons in the original hydrocarbon are progres sively loosened.
• P o l y a c r y l i c Rubber Vulcanization T h e mechanism of vulcanization of polyacrylate esters induced w i t h sodium m-silicate and with l e a d oxide was the the subject presented b y S. T. Semegen, B. F. Goodrich. Analysis of the distillates from vacuum distillation at curing tem peratures of the rubber, the rubber plus curing agent, and the cured rubber indi cated alcohol liberation. This was cred-
At Bell Telephone Laboratories, F. H. Winslow pipets cross-linked polydivinylben zene spheres. W. O. Baker shows portion of same batch of polymer spheres, thermally dehydrogenated to carbon without fusion or change of shape
• Polymer Carbon A hard dense carbon, produced by the dehydrogenation at high temperatures of solid, highly cross-linked hydrocarbon
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