bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Determination of Sulfur in Rubber by Means of the Calorimetric Bomb
Authors: Saladini B. 
Published: February 2011

Abstract
For determining the total sulfur content of rubber, industrial laboratories ordinarily use some method which is based on the destruction of the organic substances, and oxidation of the sulfur to sulfur dioxide in an open vessel, e. g., by sodium peroxide, perchloric acid, or a potassium carbonate-potassium nitrate mixture. Particular attention should be called to the method of Butironi which is based on the fusion of the substance with dry potassium hydroxide in a silver crucible, and subsequent oxidation of the sulfur to sulfuric acid by potassium nitrate. This method can be used for hard rubber. There is also an interesting method of Losana, which involves heating the substance with powdered iron and sodium bicarbonate, treatment of the iron sulfide with hydrochloric acid, passage of the hydrogen sulfide into zinc acetate solution, addition of a known excess of iodine solution, and titration of the excess iodine. All these methods are tedious and delicate, and leave much to be desired from the point of view of precision because of losses through spattering or incomplete oxidation. Because of this, and because of the great simplicity and rapidity of execution with many organic substances other than rubber, the possibility of utilizing the calorimetric bomb for the determination of sulfur in rubber was investigated. Many tests on mineral oils and organic substances containing sulfur have proved the simplicity of the method and the certainty of perfect combustion and complete oxidation of the sulfur when the procedure is carried out with proper skill.
The Absorption of Water by Rubber and Its Relation to the Protein Content
Authors: Skinner S. J. , Drakeley T. J. 
Published: February 2011

Abstract
1. The absorption of water by rubber is dependent upon the degree of division, and comparable results are obtained in a reasonable time only by using shredded samples of rubber. 2. The moisture in rubber appears to be present in two forms, (a) that removed after, say, three days, over sulfuric acid, and (b) what has been termed the residual moisture, which is more difficult to extract from the rubber, but which is evolved by heating the sample for an hour or so at 100° C. In general, the higher the protein content the lower the percentage of residual moisture. 3. Solutions of sulfuric acid provide suitable means of adjusting the humidity of the air. 4. The temperature must be kept constant to avoid deposition of dew upon the rubber. 5. The rate of absorption of moisture decreases rapidly after the first 24 hours of exposure to the prescribed atmosphere. The absorption after 5 days is very slow, and equilibrium was attained in approximately one week. 6. In general the rate of absorption is higher with rubbers containing a large percentage of protein matter. The rate of absorption in an atmosphere of humidity of less than 80 per cent is slow, and for experimental purposes a humidity of approximately 95 per cent is shown to be suitable. 7. It has been found that the ratio of the water absorbed at a constant humidity to the residual moisture is in all cases related to the protein content. 8. In general, the total weight of water absorbed per 100 parts of rubber rises with rising protein content provided the humidity of the air in contact with the rubber is 85 per cent or higher. 9. The proportion of moisture absorbed in atmospheres of less than 70 per cent humidity is small, but increases rapidly with increasing humidity.
Experiments on the Electrodeposition of Rubber from Latex
Authors: Mackay J. G. 
Published: February 2011

Abstract
Freshly tapped latex contains on the average from 27 to 35 per cent of rubber and from 1.2 to 1.7 per cent of acetone-soluble matter, such as resin and water-soluble sugars, from 1.5 to 2.0 per cent of protein and 0.25 to 0.20 per cent of mineral matter. The last consists mainly of the phosphates of calcium, magnesium, and potassium, with organic salts of these metals and a small amount of sulfate. Doubts have been expressed as to the existence of rubber as such in latex, since the physical properties of the dispersion bring it within the category of emulsions, i. e., of dispersions whose dispersed phase is liquid. Thus it has been suggested that the dispersed particles must consist of some simpler hydrocarbon which is polymerized to rubber during coagulation. From results obtained with the micro-manipulator, Freundlich and Hauser (Kolloid-Z., 36, 75 (1925)) concluded that the particles in latex consist of an elastic (solid) outer skin containing a viscous liquid, and assumed that the inner liquid hydrocarbon and the outer solid represent different stages of polymerization of the basic hydrocarbon isoprene C5H3. It is, of course, quite probable that the ejection of liquid which these investigators observed when a latex particle is punctured resulted from the rupture by the needle of the field of force at the surface of a liquid particle, and it is perhaps advisable to adhere to the more conservative conclusion of Stamberger (“The Colloid Chemistry of Rubber” (1929)) that in all raw rubber dispersions we are mainly concerned with liquid disperse phases. Latex is a relatively coarse dispersion with an average particle size of 0.5μ, and the particles vary in size from 2.0 to 0.1μ, i. e., from microscopic to ultra-microscopic particles (von Weimarn, Kolloid-Z., 46, 217 (1928)).
Isoprene and Rubber. Part 33. End Groups in Rubber
Authors: Staudinger H. 
Published: February 2011

Abstract
In a recent work, Pummerer, Ebermeyer, and Gerlach attempted to identify end members in the rubber molecule by ozone decomposition, and in this way to determine the molecular weight of rubber by chemical means. In this connection they say: The basis for the validity of the conclusions derived from the cleavage fragments on the average length of the rubber chain is that this hydrocarbon contains no structurally foreign impurities, but is built up of homogeneous molecules, though of perhaps different lengths. Pummerer abandons his earlier view, according to which rubber is composed of a uniform base molecule, in favor of concepts held by me for years on the constitution of rubber and other high polymeric substances. As was first proved for synthetic products and as shown for balata and rubber, these substances consist of a mixture of similarly constituted molecules of various lengths and therefore of a mixture of homologous polymers. Pummerer has now adopted this concept, but on the other hand he does not agree on the question of the molecular weight.
Isoprene and Rubber. Part 34. Molecules or Micelles in a Rubber Solution
Authors: Staudinger H. , Bondy H. F. 
Published: February 2011

Abstract
Measurements of the Viscosity of Rubber Solutions In the literature may be found numerous measurements of the viscosity of rubber solutions, the object of which was to throw light on the nature of colloidal solutions and changes in these solutions by various operations. These investigations give no insight into the structure of colloid particles and the reason for changes in rubber solutions because they are based on false assumptions, particularly the assumption that rubber has a micellar structure. Often highly viscous solutions were studied, and though these appeared to be of special interest to the colloid chemist, they were unsuited for such investigations, for they are gel solutions in which the structure of the colloid particles is much more difficult to explain than is that in dilute solutions (sol solutions), where the molecules have freedom of movement and do not disturb one another. The earlier works also contain references to the sensitivity of rubber to oxygen, though no special precautions were ever taken in the measurements to exclude oxygen; in fact this was unnecessary as a rule, for crude rubber solutions are much more stable, because of anticatalysts present, than solutions of pure rubber in which these have been removed. Pure rubber was prepared by the method of Pummerer and Pahl and, as described in the following work, was separated by fractional extraction into portions of different average molecular weights. Viscosity measurements of the individual fractions were then carried out under various conditions. The study of the rubber solution, like that of the balata solution, must be carried out with complete exclusion of air, and the solvent (tetralin or benzene) must be distilled in an atmosphere of pure nitrogen and be freed of oxygen. The filtration of the rubber solution, the filling of the viscosimeter, as well as the measurements themselves, are likewise made in an atmosphere of pure nitrogen. Measurements were taken in the Ubbelohde viscosimeter at different pressures, as a rule at 10.30 and 60 cm. mercury pressure. Very dilute solutions were also measured in the Ostwald viscosimeter, since the deviations from the Hagen-Poiseuille law are of no great importance at low concentration. Finally, it should be mentioned that these special precautions during the viscosity measurements, above all the careful exclusion of air, are necessary only in the case of rubber, not with the saturated hydrocarbons, polystyrene, and hydrorubber.
The Minimum of Sulfur Required for Vulcanization. A Résumé
Authors: Bruni G. 
Published: February 2011

Abstract
The problem of the minimum proportion of sulfur necessary to effect vulcanization is fundamental to an interpretation of the very nature of vulcanization itself. Since the introduction of ultra-accelerators, it has been recognized that very small quantities of sulfur are sufficient to bring about vulcanization. In experiments carried out in 1918 in collaboration with G. Menghi in the Laboratory of Chemical and Physical-Chemical Research of the Pirelli Company of Milan, the author found that by the aid of zinc dimethyldithiocarbamate or of similar substances there is an appreciable vulcanization with 0.2 per cent of sulfur. This fact was made public in patents applied for by the author the next year. On the other hand, it is generally recognized today that all vulcanization originates in a chemical reaction, though a fundamental difficulty lies in the fact that it has never been possible to give an exact definition of what is meant by vulcanization. When is a rubber considered vulcanized? From a technical point of view this question may be answered, but there has not been a satisfactory explanation up to this time.
Applications to Rubber of the Concept of Antioxygens and Proöxygens. The Case of Litharge
Authors: Dufraisse Charles , Drisch Nicolas 
Published: February 2011

Abstract
It is known that the oxidation of autoöxidizable substances can be retarded or accelerated by the addition of a small proportion of certain compounds. To these latter Moureu and Dufraisse have given the name antioxygens and prooxygens, have shown that they act catalytically, and have proposed a theory to explain their action. Like other autoöxidizable substances, rubber is sensitive to pro- or antioxygenic catalysis, and this fact is of particular interest, since autoöxidation is one of the principal causes of its spontaneous deterioration or aging. It seemed worth while therefore to undertake a systematic study of this oxidation, with the hope of drawing practical conclusions in connection with industrial processes and the preservation of rubber. The change brought about by autooxidation is a complex phenomenon, and only when each of the factors is studied separately can exact conclusions be reached. In our case we have tried to, distinguish each of the influences which may play a part. In our study we used the experimental method of Moureu and Dufraisse, which in principle involves measuring the rate of oxidation by the manometric method in the cold and at 80°. Since earlier observations and our own preliminary experiments showed that oxygen in the proportion of 1 to 100 was sufficient to make the rubber useless, all our experiments are concerned only with the beginning of oxidation.
A Simplification and Improvement in the Determination of Copper in Fabrics and Rubberized Materials
Authors: Kirchhof F. 
Published: February 2011

Abstract
The determination of small quantities of copper in fabrics and in rubberized materials can be simplified by destruction with concentrated nitric acid, which accelerates the ignition to the final ash. At the same time, this method avoids the usual danger of volatilization of copper as chloride as a result of the presence of chlorine from white factice or from cold vulcanization. Likewise, precipitation of the copper as sulfide can be avoided by repeating the precipitation of the extract from the ash, which contains predominantly aluminum and iron, with ammonia. In this second precipitation, only around 1 to 2 per cent of the total quantity of copper is retained in the precipitate and filter, and this quantity may in most cases be neglected. The ordinary colorimetric method used in the past for the detection of copper as complex cuprammonium ion can be made about ten times as sensitive by making use of the reaction: Cu+ + + 2I− → CuI + I. This is, however, applicable only in the complete absence of the ferric ion and of nitric acid in the test solution. The sensitivity can be increased still more by the addition of starch. Another advantage of the determination of copper by measurement of the equivalent quantity of iodine lies in the fact that, if necessary, only one-tenth as much sample need be used, but in this case as in all such determinations, the copper must be distributed uniformly throughout the material to be analyzed.
Lipin from Latex
Authors: Cotton F. Harriss 
Published: February 2011

Abstract
Recent papers by Rhodes and Bishop and by Eaton, Rhodes, and Bishop have described work carried out at the Rubber Research Institute of Malaya on the isolation of lipin from the serum of latex, and its effect on vulcanization. Aside from its accelerating power, it was found that when it was added to rubber during mastication on hot rolls, the plastic mass became opaque and had a great tendency to crumble. The receipt of about four ounces of lipin extracted from Hevea latex gave the opportunity to verify this peculiar effect of lipin on rubber during mastication and to find some industrial application of this property. Approximately two hundred grams of pale crepe rubber were masticated on a small experimental mill until the rubber ran around the front roll in a smooth sheet. Two grams of the waxy lipin were then added. This did not adhere to the rubber, but rolled around in a lump on the bank of rubber at the nip. As the surface of the masticating rubber became smeared with the lipin, the sheet coming around the front roll began to break up, as if it were scorching, and in a few moments the rubber began to crumble like vulcanized scrap being shredded. After a time, the lipin worked into the rubber, which then reunited in the form of a sheet.
Reactions during Vulcanization. II Reaction between Zinc Soaps and Mercaptobenzothiazole
Authors: Depew Harlan A. 
Published: February 2011

Abstract
Fatty acids react rapidly with zinc oxide to form zinc soaps during milling, and accordingly the action of fatty acid in the presence of zinc oxide is the same as that of an equivalent amount of the corresponding zinc soap. In accelerated stocks, the zinc soaps in the mix react with the accelerator to form the active zinc accelerator compound. The dynamic equilibrium between the accelerator and zinc soaps results in the formation of a smaller amount of the zinc accelerator compound in the case of mercaptobenzothiazole than for many accelerators, and accordingly relatively large amounts of zinc soaps are required with it. Since the zinc reacts with mercapto benzothiazole as the zinc soap, and since there is sufficient time for the reaction between zinc oxide and the fatty acid to proceed to practical completion, irrespective of the particle size of the zinc oxide, it follows that particle size of the zinc oxide is not a factor in the activation of mercaptobenzothiazole.
Effect of Cadmium Compounds on Typical Organic Accelerators during Vulcanization
Authors: Easley M. K. , Eide A. C. 
Published: February 2011

Abstract
Cadmium may occur in zinc oxide in the form of oxide, hydroxide, sulfate, sulfide, chloride, and carbonate in quantities up to 0.5 per cent or slightly more. Using 10 parts of zinc oxide which contains 0.5 per cent of cadmium, the latter would not exceed 0.05 part on the rubber. Owing to testing inaccuracies and the masking effect of impurities, small amounts of cadmium may be difficult to detect. To eliminate such complications, a base formula was selected using chemically pure zinc oxide to which were added various amounts of cadmium compounds. With few exceptions, these compounds retard tetramethylthiouram monosulfide but slightly advance the rate of cure of butyraldehyde aniline, diorthotolylguanidine, and mercaptobenzothiazole.
Experiences with a Direct Accelerator-Adsorption Test
Authors: Amon F. H. , Estelow R. K. 
Published: February 2011

Abstract
A method for determining the accelerator adsorption properties of carbon blacks is described. This method is novel in that an extremely dilute solution of diphenylguanidine in benzene is employed. Application of the test to a large number of carbon blacks has revealed its practical value as a measure of those variations in adsorption properties which are of teal significance to the rubber manufacturer. The method has been employed in several separate control laboratories and it has been found to be of distinct value in indicating quality of production. Since the results can be interpreted without knowledge of source or history of the particular carbon black being tested, the test can be employed for control purposes by the rubber manufacturer as well as by the carbon black manufacturer.
Variations in Plantation Sheet Rubber
Authors: Bishop R. O. , Fullerton R. G. 
Published: February 2011

Abstract
An examination of the samples of sheet rubber collected at a recent Exhibition discloses a high degree of variation in the vulcanization properties of the rubber. Similar variations in the normal produce of first class estates are recorded. Other properties of rubber, such as plasticity, may be expected to show similar variability. Figures are given to indicate the extent of the irregularities and how they would be reflected in technical mixes. The bearing of this on the industrial uses of raw rubber is discussed.
An Inorganic Rubber
Authors: Renaud Paul 
Published: February 2011

Abstract
The hypotheses generally accepted for the structure of gels explain these phenomena in detail. The trimer, polymerized by heating, gives rise to chains of different sizes, which are able to unite and form a network. The latter contains in its meshes the trimer which has not reacted, and also polymers of low molecular weight. According to whether the latter form a liquid or solid mixture, the gum is optically liquid or solid. At low temperature, the network itself assumes a rigidity which it communicates to the entire mass. The thermo-mechanical properties show that this is true of all the gums. The presence of the network has little influence on the fusion of the intercellular product, whereas its influence on vaporization is great; in fact, the volume is as little affected by fusion as it is greatly changed by vaporization. It must therefore be the case that rupture of the meshes by pressure is more rapid than their formation by polymerization. The influence of benzine and of water, one of which dissolves the intercellular products and the other does not, shows the influence of osmotic pressure, to which Duclaux (see Bull. soc. chim., 33, 36 (1923)) has called attention.
Note on the Absorption of Oxygen by Sheets of Rubber
Authors: Linhart George A. 
Published: February 2011

Abstract
Very interesting and commercially very important experiments have recently been made in the Bell Telephone Laboratories by G. T. Kohman on the absorption of oxygen by sheets of rubber. No attempt, however, was made to interpret the results mathematically. It is true, of course, that any empirical equation to express the course of the process would be merely a sort of garnish. It would be interesting, however, to show that these processes are not unique. Some years ago the writer published an equation which described the progress of many processes in the fields of chemistry, botany, biology, bacteriology, etc. It is based upon the results of the tossing of a coin, and represents in fact the law of uni-directional probability. The derivation of the equation is rather lengthy. In this note the equation will be applied to the process of the absorption of oxygen by sheets of rubber. In the original article cited above the numerical data are not given, but they are so well shown on the graphs that the results may be read off to within one per cent. The amounts of oxygen, therefore, given in the table of this note are expressed in millimeters read off on the original graph, while the time is expressed in hours.
Coherent Expanded Aerogels
Authors: Kistler S. S. 
Published: February 2011

Abstract
There are few topics in colloid chemistry that have experienced such extensive investigation as that of the structure of gels. Numerous hypotheses have been presented and supported by experimental data of one character or another. Certain aspects of gels have seemed to classify them as solid solutions, others as emulsions, while yet others give strong support to a two-phase, solid-liquid structure. Although the latter theory in similar form to that postulated by Nägeli in 1858 has been accepted by most of the foremost colloid chemists, the evidence has not been sufficiently unequivocal to convince all. The evidence presented in the results of diffusion experiments through gels, the fact that the electrical conductivity, refractive index, and vapor pressure before and after setting are identical, at least in certain cases, and the known facts of syneresis would seem to leave little room for doubt of the two-phase nature of gels in general. A theory in order to be perfectly acceptable must, however, enable verifiable predictions to be made from it.
Further Studies of Rubber Solutions
Authors: Shacklock Cecil W. 
Published: February 2011

Abstract
1. The refractive index of rubber is not appreciably affected by mastication for five hours in the cold. 2. The refractive index of solutions of rubber indicates that solvation of the rubber hydrocarbon is independent of the time of milling of the rubber. 3. The oxygen, which is continuously absorbed by rubber during mastication in air, reacts with the rubber, evolving oxidation products, and also forms addition products. It is suggested that this addition of oxygen reduces the micellar binding forces and so permits easy mechanical disaggregation. 4. The acetone extraction of rubber increases progressively with the period of mastication of the rubber. 5. The surface tension of solutions of rubber milled for varying periods increases with the time of milling, and subsequently remains constant. This is possibly due to the oxidation products from the end-groups of the hydrocarbon chains. Such end-groups are more open to attack by oxygen than the rest of the chain; further, there is a limit to the number of end-groups available for reaction (two per chain) while the number of unsaturated linkages between the end groups is undoubtedly many, and each of these is a possible point of oxygen action.