bluuebunny/crossref_metadata_2025 huggingface dataset:
Refractive indices of polythenes with different degrees of branching
Authors: Baccaredda M. , Schiavinato G.
Published: April 2003

Refractive indices of five polythene samples, previously studied by Bryant and Franta and by Muthana and Mark, who determined their densities, degrees of branching, osmotic molecular weights and μ‐values in xylene solutions, have been measured by the immersion method in suitable liquid mixtures. Powdered samples have been prepared from xylene solutions by cooling and by evaporation of the solvent under identical conditions. They appear, under the microscope, as transparent radial and weakly birefringent spherulites; refractive index values are higher than those of the amorphous polythene and decrease as the degree of branching increases. The refractive index lowering is to be ascribed to the change both of the molecular structure (branching) and of the ratio between the amount of amorphous and of crystalline material, the latter strictly depending on the former when samples are prepared under identical conditions. Measurement of the refractive index may therefore be suitable for the empirical determination of the degree of branching in polythenes; it seems to be simpler and more significant than the measurement of the density, the latter also being affected by relatively large microvoids, while the refractive index may be affected only by those microvoids the sizes of which are not larger than the wave length of the light used. Refractive index measurement may also be suitable for the determination of the degree of branching and of the degree of crystallinity in other polymeric substances.
Problems in the physical chemistry of polyelectrolytes
Authors: Katchalsky A.
Published: April 2003

This paper reviews some aspects of the present state of research in the field of polyelectrolyte solutions. It deals mainly with synthetic polyelectrolytes with special attention to their electrostatic potentials, the colligative properties of their solutions and molecular shape changes.
Interaction between polyelectrolytes and heteropolar precipitates
Authors: Težak Božo , Kratohvil Stanka
Published: April 2003

The interactions of some polyelectrolytes (anionic–gum arabic, agar; ampholytic–gelatin) with silver bromide sol in statu nascendi were studied. It was found that there are analogous phenomena to those encountered with usual hydrophobic sols. The polyelectrolyte effects on hydrophobic systems were treated in a manner usual for simple electrolytes. The appearance of the typical coagulation curves with maximum is used for the characterization of various systems: hydrophobic colloid–polyelectrolyte–electrolyte. Depending upon the position of the system on “stabilizing” or “sensitizing” side of this maximum (sometimes of minimum), there is a very pronounced difference of the polyelectrolyte action on the coagulation value of simple electrolyte. Thus, on the “stabilizing” side, the “reverse” antagonism was found, which is explained as a result of the dominating polyelectrolyte adsorption effect.
A dielectric study of a carboxymethylcellulose in aqueous solution
Authors: Allgén Lars‐Göran , Roswall Siw
Published: April 2003

A carboxymethylcellulose sodium salt (CMC) with about 50% of the glucose units substituted, has been studied dielectrically by the “ellipsoid method” at various wave lengths. Aqueous solutions containing 0.1–0.0025 g./100 ml. were investigated. Dielectric increments of 2–9 dielectric constant units were obtained for these solutions. The calculated increment per gram per liter was not constant but increased considerably at the lowest concentrations, indicating the prevalence of polar molecules or aggregates at the lowest concentrations, whereas less polar aggregates dominate at higher concentrations (more than 0.01% solutions). At the lowest concentration studied, 0.0023%, the increment per gram per liter was about 120, corresponding to a molar increment of about 55,000,000. Dielectric dispersion curves were obtained which approached theoretical Debye dispersions, indicating that the CMC molecules are rather rigid. The dispersion curves were displaced toward shorter wave lengths with increasing concentration, probably due to the strong molecular interaction. At the lowest concentration a relaxation time of 4.6 × 10−7 sec. was calculated for the CMC molecule. This corresponds to a rotation of the molecules about their long axes in the electric field. An average molecular weight of about 460,000 was calculated for the CMC molecules, or polar aggregates, in very dilute aqueous solution. The electric moment of CMC was estimated to be about 1000 Debye units. In contrast to CMC, the uncharged polysaccharides dextran and ethyloxyethylcellulose did not show any deviation of the dielectric constant values from that of the pure solvent, when investigated in 0.5% aqueous solutions at various wave lengths. It was concluded that the dielectric properties of CMC are very similar to those of other polyelectrolytes studied–such as desoxyribonucleic acid, nucleohistone, and hyaluronic acid.
Separation of neutral proteins on ion‐exchange resins
Authors: Boardman N. K. , Partridge S. M.
Published: April 2003

The effect of pH of buffer on the adsorption of cytochrome C on the ion exchange resin IRC 50 has been studied in detail and the information gained has been used to predict conditions for the separation of neutral proteins such as the hemoglobins. The behavior of a protein on the resin is markedly different from that of ampholytes of low molecular weight such as the basic amino acids. The basic amino acids are desorbed as the pH falls below 5 due to suppression of the ionization of the resin carboxyl groups, but the adsorption of protein is greatly increased under acidic conditions. It is suggested that this is due to a large increase in secondary short‐range forces.

Sheep fetal CO hemoglobin has been separated from bovine CO hemoglobin and bovine CO hemoglobin from bovine methemoglobin. The eluting buffer was citrate of pH 5.81 and 5.92, respectively, and Na+ concentration 0.34 g. ions per liter. In initial experiments, heavy losses of the CO hemoglobins occurred which was most probably due, to a large extent, to the formation of methemoglobin. To obtain good yields, it is necessary to work at a temperature near 0°C. and to use freshly prepared proteins.
La courbe de titration de l'insuline et de ses fractions
Authors: Fredericq Eugene
Published: April 2003

On a mesuré au moyen d'une électrode de verre les courbes d'électrotitration de l'insuline cristalline dans KCl 0,1 N, depuis pH 2 jusque pH 11. Dans la région alcaline les courbes ne sont pas réversibles. La solubilité de l'insuline entre pH 7 et pH 9 augmente beaucoup lorsque la protéine a été préalablement dissoute en milieu acide ou alcalin. Les quantités d'ions H libérées dépendent aussi du traitement subi antérieurement.

On a séparé l'insuline en deux fractions suivant leur solubilité à pH 8. La fraction la plus soluble a une courbe de titration réversible en milieu homogène; dans le domaine d'insolubilité de l'insuline (pH 4 à 6,5), la courbe dépend du sens de la titration. La fraction la moins soluble révèle un nombre inférieur de groupes titrables en milieu alcalin. Ce nombre augmente par séjour à pH supérieur à 10. Les changements survenus dans les groupes dissociables ont été interprétés comme indiquant la présence de liaisons spéciales dans lesquelles seraient impliqués des groupes phénoliques et des groupes imidazole.

On a calculé des courbes de titration suivant la théorie classique et suivant la théorie de Debye‐Hückel. On a pu rendre compte des résultats expérimentaux en assignant une seule constante de titration aux groupes de měme espèce déduits de l'analyse chimique, sauf pour les groupes phénoliques. La théorie des interactions électrostatiques permet d'interpréter ces faits. Elle fournit des valeurs de pK′0 en bon accord avec les données obtenues avec d'autres protéines. Les pK′0 sont respectivement de 6,6, 7,8, 9,9 et 10,0 pour les groupes imidazole, α‐aminé, phénolique et ε‐aminé.

En utilisant comme solvant du dioxane à 40% dans une solution aqueuse 0,4 N en KCl, on a pu maintenir l'insuline en solution dans tout le domaine de pH. La courbe de titration a été mesurée dans ce milieu et interprétée théoriquement par l'effet de l'abaissement de la constante diélectrique sur les constantes de titration.
Interaction of vegetable tannins with polyamides as proof of the dominant function of the peptide bond of collagen for its binding of tannins
Authors: Gustavson K. H.
Published: April 2003

The irreversible fixation of vegetable tannins (mimosa) by collagen and esterified collagen, as well as by a hydrated polyamide, has been investigated. The polyamide possesses a marked affinity for the vegetable tannins and binds them irreversibly, proving that the peptide linkages function as binding sites for vegetable tannins. This fixation is independent of pH value of the system in the pH range 2–8. The same independence is shown in the fixation of tannins by collagen from solutions containing sodium chloride which prevents the swelling of collagen. The typical fixation curve of vegetable tannins by intact collagen is highly pH‐dependent. In this instance the tannin fixation is directly related to the degree of swelling of collagen as a function of the pH value of the system. This is due to the fact that the degree of swelling of the protein governs the number of coordination‐active peptide bonds present in collagen for the fixation of tannins. Esterified collagen, in which the major part of the potential hydrogen binding sites are free to react, fixes large amounts of tannins independently of the hydrogen‐ion concentration of the system in the pH range 2–7. The rapid drop in fixation of tannins at pH values >8 is due to the ionization of phenolic groups, leaving fewer hydrogen bonds available on the tannin molecule. Evidence is presented in support of the view that the main reaction of polyphenolic tannins of the major type represented by mimosa tannins consists in coordination of a polyphenolic molecule to peptide bonds of adjacent protein chains, probably by means of hydrogen bonds. This multipoint attachment will explain the stabilization of the protein lattice effected by the tanning agent.
Application of an integrator in the calculation of diffusion coefficients from plotted diffusion curves: Theory and practice, including an estimation of the accuracy of the method illustrated also by the calculation of a set of known Gaussian curves
Authors: Jensen Robert
Published: April 2003

The formulas used for calculation of diffusion coefficients in free diffusion are stated. The calculations request the 0th, first, and second moments of the curve to be calculated. This is usually made by calculation of moments of segments of the figure between the curve and the base line, followed by summation.

It is proposed to replace this rather laborious procedure by the use of an integrator. A survey is given on the theoretical background and the principles for such instruments. Some equations are stated for the type of instrument used in these investigations. From these equations it is possible, by inserting the values in the formulas used for the calculation of diffusion coefficients, to express the latter for a certain curve as a function of the rotation of the three integration rolls in the instrument. The relative influence on the final result for these integration rolls is considered. For one of the rolls this can be shown to be insignificant, when the moment axis is chosen very near the central axis of the curve. Our experience has shown the standard error in a normal measurement to be 2 × 10−3 and 3 × 10−3 of a revolution for the two other integration rolls. Some curves are given which show the requests one must put on the relative number of rotations for these rolls to make certain that the relative standard error, introduced by the integrator, will not exceed certain values on the final result. The curves are drawn for values from 2 to 0.1%.

From a known Gaussian distribution a set of diffusion curves is drawn. The diffusion coefficient is calculated from these curves both by the usual method and by the integrator. The results obtained by the integrator compare well with those by the usual method if the peaks are not drawn too narrow.
Two‐dimensional electrophoresis on paper
Authors: Dicastro Gino
Published: April 2003

With a view to finding a better method of separating the different components during electrophoresis on paper, we have carried out the electrophoresis in two dimensions, first flowing the current in one direction and then at right angles to that direction. For this purpose we used square paper sheets between two glass plates of the same dimensions. The electrical behavior of the material to be analyzed was tested before electrophoresis, so that it was possible in each instance to establish the duration and the different electrical characteristics of the two periods of electrophoresis and also the best initial position for placing the material. The experiments show that the components are found along a straight line, the position of which is determined in the plane by the characteristics and time flow of the current during the two phases of the process. Referring to the initial position of the material, each individual component is to be found at the extremity of the hypotenuse of a right angled triangle, the other sides of which are formed by the paths made by the substance in the two different phases of the process. The obvious advantage of the two‐dimensional electrophoresis on paper is that it is possible to trace, on the same sheet of paper, the path taken by the different components under two different electrical conditions.
Degradation of vinyl polymers in solution
Authors: Tasset G. , Smets G.
Published: April 2003

The degradation of high polymers was studied in dilute solution (1%) in the presence of an equivalent amount of benzoyl peroxide in a temperature range from 65 to 100°C.

The reaction was followed dynamically by a viscometric method, and from a static point of view by determining the polydispersity of the samples after degradation, and also by spectrophotometric measurements. The viscometric method allows examination of the influence of the polymer concentration, of the degree of polymerization, of the initiator concentration, of the temperature, and of the chemical structure of the polymer on the rate of degradation. These rate constants were obtained under the same experimental conditions, and permit the classification of the polymers in the following decreasing order: polychloroacrylate, polymethyl methacrylate, and polystyrene. Under the same conditions, polyvinyl chloride and acetate are stable and not affected. These results are discussed as a function of the lability of some atoms present in the polymeric chain and as a function of the relative stability of the intermediate radicals produced during the reaction. Statically, the degradation was followed by determining the variation of polydispersity before and after degradation in the case of a sample of polymethyl methacrylate. On the other side, ultraviolet spectrophotometry shows the presence of monomer by degradation of a polystyrene sample; this spectrophotometric method also allows proof of the microreversibility of the polymerization process. The use of this technique makes it necessary to carry out the experiments under experimental conditions that differ from the preceding ones (lauroyl peroxide, and chloroform as solvent).
The lactam‐amino acid equilibria for ethylpyrrolidone and polyvinylpyrrolidone
Authors: Frank H. P.
Published: April 2003

The lactam‐amino acid equilibria of N‐ethylpyrrolidone and poly‐N‐vinylpyrrolidone were studied in dilute aqueous solutions and in n‐butanol at 100°C. and compared with earlier investigations of similar systems. It was found that with in the intermediate pH range the lactam is the predominant form. Below and above certain critical acid and alkaline pH values increasing amounts of amino acid will be formed. It has been shown that these critical pH values are closely related to pK1 and pK2 of the corresponding amino acid. The polymeric lactam PVP is more resistant against hydrolysis than the low molecular lactams. This effect is due to the polyampholyte character of the polymeric amino acid formed in the course of the hydrolysis reaction.
Polyvinylpyrrolidone. I. Distribution of molecular weights: Experimental methods and applications
Authors: Campbell H. , Kane P. O. , Ottewill Ingrid G.
Published: April 2003

A method is described for determining the distribution of molecular weights of polyvinylpyrrolidone (P.V.P.) by measurement of the turbidity produced in aqueous solution by varying concentrations of sodium sulfate. Using this method, the acetone‐water method of fractionation is shown to be unsound due to inhomogeneity of the fractions obtained. This latter method is, however, of value in the preparation of P.V.P. of narrow molecular weight ranges by repeated fractionation. The distributions of molecular weights of typical samples of P.V.P. used in the plasma substitute, Plasmosan, are given. Less than 5% by weight of the molecules possess a molecular weight greater than 100,000. The reproducibility and stability to autoclaving of this polymer are shown to be satisfactory.
An approach to the solution of structure problems of organic chain polymers
Authors: Bjørnhaug A. , Ellefsen Ø. , Tønnesen B. A.
Published: April 2003

A radial distribution method for interpreting diffuse x‐ray diagrams of liquids has been utilized and further developed for an approach to the solution of structural problems of unoriented specimens of chain polymer substances. The principles of the technique have been given. Experimental distribution curves, indicating the atomic distance distributions have been calculated for the following chain polymers: polyvinyl acetate, polyvinyl alcohol, polystyrene, polyhexamethylene adipamide, polymethyl methacrylate, regenerated cellulose, and alginic acid. For the structure interpretation some of the experimental distribution curves are directly compared with theoretical distribution curves calculated from the atomic distances in measured out structure models, which have been built up on a scale of 1 A. equal to 10 cm. by means of a molecular model building set. From the results obtained, the technique seems to be well suited for structure investigations of unoriented samples of polymer substances.
The electrostatic free energy of polyelectrolyte solutions. II. Fully stretched macromolecules
Authors: Lifson S. , Katchalsky A.
Published: April 2003

(1) The electrostatic internal energy of a solution of rodlike, ionized polymolecules is calculated by an integration which makes use of the molecular potentials evaluated previously. (2) The electrostatic free energy is calculated by a charging process for which the reference state is a discharged solution of the same concentration as that of the charged solution. (3) A series of graphs is presented for the numerical evaluation of the internal and free energies of salt‐free polyelectrolyte solutions as a function of concentration, degree of ionization, and temperature. (4) The osmotic pressure of stretched polyelectrolytes is calculated from the free energy expression. The calculated osmotic coefficients are practically independent of molecular weight and polyelectrolyte concentration, and are determined by the degree of ionization. A comparison with the measurements of Kern on salt‐free polyacrylic acid at higher degrees of ionization (for which the macromolecules are stretched) gives a very satisfactory agreement. (5) An expression for the light scattering by polyelectrolyte solutions is derived from the equation for osmotic pressure and discussed briefly.
Polyampholytes
Authors: Katchalsky A. , Miller Israel R.
Published: April 2003

Six amphoteric copolymers of different composition of 2‐vinylpyridine and methacrylic acid were investigated. The specific viscosities of the copolymer solutions exhibit a pronounced minimum at the isoelectric point and the spectrometric titration of the pyridinium groups shows a pronounced jump in pH at the isoelectric degree of ionization. A theory of the polyampholyte behavior, based on the shape changes of the macromolecules and the field energy of the ionized groups, is developed and compares satisfactorily with the experimental results. The theory permits inter alia the evaluation of the intrinsic dissociation constants of the monomeric units and the determination of the isoelectric points from copolymer composition.
Dissociation of weak polymeric acids and bases
Authors: Katchalsky A. , Shavit N. , Eisenberg H.
Published: April 2003

The electrolytic dissociation of several polymeric acids and bases in aqueous solutions has been investigated. The potentiometric behavior is well described by the following equations, For polyacids:

and for polybases:

pK0 is the intrinsic dissociation constant of the monomeric unit, α and β are the degrees of ionization of the polyacid and the polybase respectively, ψ0 is the electrostatic surface potential of the polyion. It is shown that ψ0 is equal to (1/ϵ) (δFe/δv) for polyacids and (1/ϵ) (δFe/δζ) for polybases where Fe is the electrostatic energy of the polyion and v or ζ the number of negative or positive ionized groups respectively. Equations for the calcualtion of ψ0 in the cases of randamly kinked and stretched polyelectrolytes are given and discussed. As the potential ψ0 can be obtained independently from electrophoretic measurements, the above equations correlate potentiometry and electrophoresis. The potentials of polymethacrylate ions were calculated from theory and obtained from electrophoretic and potentiometric measurements. The potentials obtained by the three methods agree within 3% thus justifying the use of the combined potentiometric and electrophoretic measurements for the evaluation of pK0. Application of this method to the potentiometric analysis of pectic acids gave good agreement with experiment and lead to pK0 = 3.40. Combined potentiometric‐electrophoretic analysis for polyaspartic acid gave pK0 = 3.53 and for polylsine pK0 = 10.44.
Effect of detergent on the polymerization of allyl acetate
Authors: Meehan E. J. , Kolthoff I. M. , Carr E. M.
Published: April 2003

The persulfate‐initiated polymerization of allyl acetate has been studied at 70°C. in the absence and in the presence of sodium lauryl sulfate. In the absence of the detergent a polymer of molecular weight about 800 is formed from initially homogeneous reaction mixtures at an initial rate approximately proportional to concentration of persulfate and approximately independent of concentration of monomer. The ratio of the initial rates of disappearance of allyl acetate and persulfate is about 14, corresponding to the ratio calculated from the molecular weight. With a separate phase of monomer the molecular weight is about 1000. The addition of the detergent does not increase the rate of initiation or affect the molecular weight of the polymer formed in innitially homogeneous media, although the rate of polymerization is increased somewhat. With a separate phase of monomer the polymer formed in the presence of detergent has a molecular weight of about 1300.
Choice of solvent for the viscometric determination of molecular weights of high polymers
Authors: Cragg L. H. , Sones R. H. , Dumitru T. E.
Published: April 2003

For the viscometric determination of the molecular weight of a flexible linear high polymer, a very “poor” solvent in which the osmotic slope constant B is zero (i.e., a so‐called “ideal” solvent) has several advantages over the usually preferred good ones. For example, shear effects that are very troublesome with very high polymers in good solvents become negligible or easily manageable. Moreover, in an “ideal” solvent, the “contents” K and a in the equation relating [η] and M really are constant over a very wide range of molecular weights and, since a always has the value 0.50, are more easily determined. Because the advantages seem to outweigh considerably the disadvantages, the use of an “ideal” solvent should be given careful consideration, particularly when the molecular weights are very high or cover a wide range.
Elastic properties of polvinyl chloride gels
Authors: Walter A. T.
Published: April 2003

Young's moduli are measured by a simple compression method on plasticized polyvinyl chloride (Vinylite VYNW) compounds containing from 5 to 100% polymer covering a range of approximately seven orders of magnitude in modulus. By comparing values obtained at different temperatures, it is shown that the 60‐second modulus in the range of 25°C. is largely due to entropy changes occurring during deformation of compounds containing less than about 50% polymer, but upon internal energy changes in compounds containing higher concentrations of resin. A semiquantitative description of the three‐dimensional polyvinyl chloride network existing in the soft‐gel region is arrived at from the kinetic theory of elasticity, and a network structure is suggested for the region of high resin content. A method for comparing relative solvent power of various plasticizers is suggested based on moduli determined in the soft‐gel region. Effects of polymer composition on the network structure are also discussed.
On the kinetics of anomalous flow
Authors: Mack Charles
Published: April 2003

Anomalous flow is considered to be associated with a transition of the particles, representing the units of flow from a state of greater order to a state of greater disorder or vice versa. The particles in the ordered state are, in general, understood to belong to regions where they are in positions of minimum potential energy. A change in the internal structure is accompanied by a variation in the number of vacancies or holes present. Expressing anomalous viscosity as a function of the fraction of the particles in the disordered state and of the fraction of holes present, it is shown that the rate of change in the concentration of these particles is the same as the rate of change in the concentration of the holes. The equilibrium constant is:

where η refers to a viscosity at a state near that of rest. ΔF is the change in the free energy of activation for a particle going from one state to another. This energy change is related to the change in kinetic energy, ΔEk, which permits the calculation of the mass of a particle. Experimental data are given for an asphalt whose shear rate is a power function of the shearing stress and for an asphalt whose shear rate is an exponential function of the shearing stress. It is shown that, in the first case, the degree of disorder increases with increasing stress, and that, in the second case, flow results in an orientation of the particles. In both cases the mass of a particle is considerably larger than that of a molecule. It would appear therefore that shear does not consist here in a shift of a particle from one position to another but is rather similar to slip in metals.
Second‐order transition temperature of butadiene copolymers
Authors: Gerke R. H.
Published: April 2003

Second‐order transition temperature of copolymers of butadiene and the following monomers, acrylonitrile, styrene, dimethylbutadiene, and methyl acrylate has been determined using the dilatometer method. That of polyacrylonitrile has been estimated by extrapolation of data. Mercury or 38% sulfuric acid was used as confining fluids. It has been found that the logarithm of the second‐order temperature in degrees Kelvin is a linear function of the weight fraction of monomer.
Effect of silicone coatings on denaturation of egg albumin
Authors: Kukin Ira , Rochow Eugene G.
Published: April 2003

Human blood is known to coagulate much more slowly in glass vessels lined with a very thin film of methyl silicone than in similar vessels with clean glass walls. In an attempt to explain this observation, the effect of various surfaces on the simpler system of egg albumin in aqueous buffer was studied. It was found that little or no denaturation of the albumin occurred when the solution of it was shaken for extended periods in either clean glass or silicone‐lined bottles in the absence of air. In the presence of a gas interface denaturation was fairly rapid, but proceeded at a somewhat lower rate in silicone‐treated bottles (coated by exposure to the vapor of mixed methylchlorosilanes) than in clean bottles. A relatively thick oily film of methyl silicone deposited by another method greatly increased the rate of denaturation, an effect due to a large degree to the increased oil‐water interface created by the dispersion of silicone oil droplets in the solution during shaking. Kinetic studies show that the over‐all denaturation is first‐order, regardless of the type of surface. A theoretical interpretation of these observations in terms of possible mechanisms is given.
The microstructure of diene polymers. II. Polyisoprenes and polybutadienes prepared at high pressures
Authors: Richardson W. S.
Published: April 2003

Polyisoprenes and polybutadienes have been prepared by bulk polymerization at hydrostatic pressures of from 5,000 to 10,000 kg./cm.2. The microstructures of these polymers have been determined by infrared analysis. In general, the structures are not grossly different from bulk and emulsion polymers prepared at near atmospheric pressure.
Kinetics of alkaline hydrolysis of pectinic acids
Authors: Katchalsky A. , Feitelson J.
Published: April 2003

The second order rate constant of the alkaline hydrolysis of pectinic acid salts decreases rapidly with the progress of the reaction and shows a pronounced positive salt effect. This behavior is interpreted in terms of an electrostatic repulsion factor and an “intrinsic” rate constant characteristic of the hydrolyzable groups. It was found that the calculated potentials (ψ) of the charged pectinic acid molecules, based on potentiometric titrations, account for the kinetic behavior as determined experimentally under controlled conditions. The intrinsic rate constant is k = 23.8 1./m. min. at 4°C.
Effect of temperature and pH on the optical rotation of proteins
Authors: Golub Morton A. , Pickett Edward E.
Published: April 2003

The effect of temperature and pH on the optical rotation of a representative group of proteins was investigated. It was found that the proteins showed little or no effect of temperature on the optical activity whether in the native or denatured state. Where definite changes in rotation occurred among the native proteins, these were attributed to denaturation accompanying the change of temperature. Zein, casein, fibrin, erepsin, globin, native and denatured egg and serum albumins, edestin, and pepsin showed no temperature dependence of optical rotation, over the temperature range 20 to 60°C., although protamine sulfate and gliadin possessed small negative coefficients. Native chymotrypsin, trypsin and β‐lactoglobulin showed a marked increase in levorotation with increase of temperature, which was due to denaturation on heating. The denatured forms of the latter two proteins, however, showed no change of optical activity with temperature. The shapes of the optical rotation‐pH curves obtained for salmine, zein, gliadin, egg and serum albumins, casein, fibrin, and insulin were found to reflect the presence of free acid‐ and base‐combining groups in the proteins, with some uncertainty in the case of globin. Since native pepsin, trypsin, chymotrypsin, and β‐lactoglobulin were denatured at pH values not far from those of their normal aqueous solutions, the rotation‐pH curves for these proteins were not capable of similar analysis, but they could be used to follow polarimetrically the course of the denaturation.
Studies on light scattering by polymethyl methacrylate solutions
Authors: Bhatnagar H. L. , Biswas A. B.
Published: April 2003

The scattering of light by solutions of a well‐fractionated sample of polymethyl methacrylate in acetone, methyl ethyl ketone, and benzene, have been measured using 4358 and 5461 A. wave lengths as incident radiations. The average molecular weights of the polymer from turbidity measurements and lengths determined from angular dissymmetries of scattered light are 571,000 and 760 A. in acetone, 38,400,000 and 715 A. in methyl ethyl ketone, and 408,000 and 375 A. in benzene. The abnormal molecular weight observed in methyl ethyl ketone solution may be ascribed to low μ – μ0 value of the medium. The greater molecular extension in ketone than in benzene solutions is explained in terms of the relative magnitudes of solute‐solvent interaction. The depolarization ratios ρu, ρv and ρh have been measured and the decrease of ρv and ρh with increase in concentration of the polymer in ketonic solvents and little change under similar conditions in benzene, are discussed in the light of the “molecular field effect” of Gans.
Variation in the lattice spacing of cellulose
Authors: Wellard H. J.
Published: April 2003

A comparative study of the unit cell parameters a, c, and β of a considerable number of cellulose specimens including samples of the four structure types cellulose I, II, III, and IV has been carried out using an evacuated camera. Small variations were observed as between samples of different origin for cellulose I and cellulose II and were most marked in the monoclinic angle parameter β and in the case of cellulose I (bacterial cellulose β = 98.25°, ramie β = 96.5°). No unit cell parameter differences greater than the experimental error were found for cellulose III, but the intensity of the (020) reflection showed large variations.
Qualitative infrared analysis of polyphenylbutadienes
Authors: De Radzitzki P. , De Wilde M. C. , Smets G.
Published: April 2003

The infrared spectra of synthetic poly‐1‐phenyl‐ and poly‐2‐phenylbutadienes have been examined, principally in the region from 9 to 15 μ. The different intramolecular structures of these polymers, corresponding to the different types of monomer additions (1,4, 1,2, and 3,4) were examined by this method; the data are in complete agreement with the chemical results as reported previously. The influence of the method of polymerization on the internal structures of the polymers is taken in evidence; the presence of the aromatic substituent in position 1 or 2 in the monomer molecule exerts a large influence on the position and the intensity of the characteristic absorption bands, if they are compared with the results for synthetic polyisoprenes.
Chemistry in carbon black dispersion
Authors: Barton Bernard C. , Smallwood Hugh M. , Ganzhorn George H.
Published: April 2003

Heating rubber‐carbon black mixtures at elevated temperatures results in vulcanizates with lower electrical conductivity, lower hysteresis, lower Durometer hardness, and increased abrasion resistance. These changes are apparently the result of chemical reactions between carbon black and rubber which alter the dispersion of the carbon black. Data are presented which show that the basic factors effecting these changes are the chemical reactivities of the carbon black and the polymer and the time and temperature of treatment.
Investigations of crosslinking in the emulsion polymerization of butadiene
Authors: Drysdale J. J. , Marvel C. S.
Published: April 2003

A study of the dilution effect of four hydrocarbons (biallyl, hexane, 3‐methyl‐1‐butene, and isopentane) on the rate of polymerization of butadiene and on the characteristics of the resulting polymer has shown that chain transfer of the following type is an unimportant reaction in butadiene polymerization:
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The above result is consistent with the kinetic treatment of crosslinking as developed by Flory. The results of a comparison of the emulsion polymerization of 2,2′‐azobisisobutyronitrile‐ and of persulfate‐catalyzed butadiene are adequately accounted for without considering the effect of the catalysts on branching or crosslinking. As previously suggested, the differences noted between 2,2′‐azobisisobutyronitrile‐ and persulfate‐catalyzed polybutadienes are probably due to a different molecular‐weight distribution. This difference in molecular‐weight distribution is partly produced by a large difference in r values for the two systems. The unmodified emulsion polymerization of butadiene with 2,2,‐azobisisobutyronitrile in an oxygen‐and peroxide‐free system produces a highly crosslinked polymer.
Viscosities of extremely dilute polystyrene solutions
Authors: Streeter D. J. , Boyer R. F.
Published: April 2003

It is shown that ηsp/c for a polystyrene fraction (M̄v = 250,000) in toluene decreases approximately linearly as the concentration is lowered from 1.0 to 0.1 g./100 ml. and then increases to a maximum at 0.001 g./100 ml. as the concentration is lowered still further. This increase in ηsp/c with dilution is a new effect which we ascribe to the expansion of polymer coils as well as to the disentangling of entire polymer molecules once the concentration is lowered to where there is ample room in the solution for each polymer molecule. The new techniques employ a viscometer with a flow time of 3893 seconds for toluene, special filtering of the solutions, and prolonged agitation of the solutions after each dilution. We present data to show that ηsp/c is time dependent at concentrations below 0.1 g./100 ml.
Calibration of light scattering photometers with Ludox
Authors: Maron Samuel H. , Lou Richard L. H.
Published: April 2003

A simple and exact method is presented for the calibration of light scattering photometers in absolute turbidity units employing du Pont Ludox as the calibration medium. It is shown that previous attempts to employ Ludox as a standard took no cognizance of the relatively high scattering power of this substance in relating τ to I90, and hence results considerably in error were obtained. To check the validity of the calibration, molecular weights were run on the standard Cornell polystyrene in toluene and MEK, and on the I. U. C. sample III polymer in MEK at both 4358 and 5461 A. The results obtained show excellent internal consistency as well as agreement with published data.
The hydrolysis of cellulose part II. Acid sensitive linkages in egyptian cotton
Authors: Sharples A.
Published: April 2003

It has been shown that a hydrolytic study of the kinetics of chain degradation can be used to detect the presence of acid‐labile linkages in cellulose, provided that the amount of ordered or crystalline material in the sample is first reduced by a treatment involving regeneration from alkaline solutions. The results for Egyptian cotton regenerated from benzyl trimethyl ammonium hydroxide in the absence of oxygen show that only a very small fraction of acid‐labile linkages—less than one per 2900 glucose residues—can be present in the original chain molecules. It is possible that even this small amount is produced during the alkali treatment. Thus weak bonds of the types proposed by Schulz and Pacsu are definitely absent. Cotton regenerated from cuprammonium and cupriethylenediamine solutions, however, does contain randomly distributed linkages which are approximately 10,000 times more sensitive to acids than the normal glycosidic type. These appear to be formed from a limited number of special sites in the chain molecules, by oxidation in alkaline solution. Assuming the value of P̄n for undegraded cotton to be 2900, the amount of these extranormal linkages is one per 660 glucose residues.
A viscometer for solutions of high polymers
Authors: Keeling C. D. , Dole Malcolm
Published: April 2003

A viscometer for solutions of high polymers having the following features is described: (1) The lower level of the capillary viscometer is determined by an overflow into an auxiliary reservoir. (2) The solutions are prepared, insoluble gel filtered, and dilutions carried out in the auxiliary reservoir. (3) Because of the fact that the viscometer is a closed system it can be rotated through 360° within the constant temperature bath, automatically filling the upper reservoir and allowing repetitive measurements to be carried out. (4) As constructed, the viscometer can only be used for solutions of low surface tension.
Solvation of cellulose nitrate in acetone‐water mixtures
Authors: Scherer Philip C. , Crookston Norbert J.
Published: April 2003

The sorption of acetone and water by cellulose nitrate from mixtures of the two solvents was studied by allowing the solid cellulose nitrate to come to equilibrium with aqueous solutions of acetone and measuring the change in concentration of the liquid phase. Changes in concentration were determined by measuring the index of refraction using a dipping refractometer. The values calculated for acetone sorbed per (C6) mole of cellulose nitrate are a function of the acetone concentration of the equilibrium solvent. Moles of water sorbed by one (C6) mole of cellulose nitrate depend inversely on the equilibrium acetone concentration of solvent.
Infrared analysis of isomerized, vulcanized and oxidized natural rubber
Authors: Salomon G. , Van Der Schee A. Chr.
Published: April 2003

The purpose of this study was to follow by i.r. analysis double bond shifts and chemical modification of natural rubber. Accurate determination of the original rubber spectrum is facilitated by the use of an internal standard. Isorubber, prepared by thermal dissociation of rubber hydrochloride, contains about 50% of double bonds in the side groups. Although a similar double bond shift is observed in the cyclization of rubber, part of the absorption, in the 11 μ region, may here be due to ring formation. Vulcanization with accelerated sulfur mixtures does not produce changes in the i.r. spectrum, unless the rubber is transformed into a derivative by overcuring with S2Cl2 or during hard rubber formation. At least three types of oxidation reactions can be distinguished spectroscopically: (1 ) degradation of the rubber (by oxidation of a rubber solution with air) with the ultimate formation of only volatile oxidation products; (2 ) gradual formation of oxygenated derivatives (oxidation with ozone), with a distinguishable structure in the spectrum; (3 ) gradual formation of an oxidized and more saturated rubber (oxidation of solid rubber with air), with less characteristic broad absorption bands.
Improved relationships for diffusion and sedimentation constants and for viscosity and streaming birefringence of solutions of polymers
Authors: Kuhn H. , Kuhn W. , Silberberg A.
Published: April 2003

For the description of the practical properties of a large number of linear polymer molecules as well as for the discussion of the various mean parameters of the individual chain molecule, the model usually employed to represent the molecule consists of N m straight line chain elements of length A m statistically joined to each other (straight element model). For the construction of large‐scale wire models of polymer molecules to be used in model experiments on the hydrodynamic behavior of chain molecules, a somewhat different model (circular segment model) was employed in previous papers. In these papers the relationships connecting the parameters which characterize these two models respectively have been determined on the basis of certain assumptions. These assumptions, as has recently been shown, were however partly in error and certain corrections have now to be applied to the numerical constants which appear in previously published formulas for the diffusion and sedimentation constants and for the intrinsic viscosity and streaming birefringence. The formulas, resulting after these corrections have been incorporated, are compiled in the present paper and the effect of these corrections on the interpretation of both new and old experimental results is discussed. It is found that agreement between theory and experiment is improved by the use of the corrected expressions and that in particular certain discrepancies which had previously existed between the lengths A m of the statistical chain element as calculated from sedimentation and diffusion experiments, on the one hand, and viscosity determinations on the other, disappear after these corrections are applied (see Table I).
Vulcanization of crepe rubber by sulfur monochloride. Part II. The dilatometric method
Authors: Glazer J.
Published: April 2003

The kinetics of the reaction between natural rubber hydrocarbon and sulfur monochloride is investigated in dilute hydrocarbon solution by the dilatometric technique. Control experiments with trilaurin and triolein show that the reaction requires unsaturated linkages in the compound to be cold‐vulcanized. The extent and rate of the nonaccelerated reaction with rubber is shown to depend strongly on the nature of the solvent. Moreover, the nonaccelerated reaction is autocatalytic in nature, and exhibits kinetics that are first order with respect to sulfur monochloride. The accelerating effects, on the reaction, of Butyl 8, mercaptobenzothiazole, dibutylammonium dibutyl‐dithiocarbamate (DBA), and methanol are investigated and it is shown that, in the presence of sufficient Butyl 8 or DBA, the autocatalytic nature of the reaction is changed to one that is kinetically of pure first order. The accelerated (Butyl 8) reaction is found to be first order with respect to sulfur monochloride. The accelerated reaction is further shown to be first order with respect to DBA and second order with respect to methanol. A free radical mechanism is proposed for the nonaccelerated reaction, involving attack by the intermediate $ \mathop {\rm S}\limits^ * {\rm \bond S \bond Cl} $ at the double bonds of the rubber molecule. It is suggested that accelerators function by reacting with sulfur monochloride to produce the active intermediate $ \mathop {\rm S}\limits^ * {\rm \bond S \bond Cl} $.
Phase equilibria in polymer–liquid 1–liquid 2 systems
Authors: Krigbaum W. R. , Carpenter D. K.
Published: April 2003

There are investigated the relations between the liquid compositions in the two phases formed when a polymer equilibrates in a mixed solvent. By imposing the simplifyng constraint that all of the polymer be located in one of the two phases, an expression for the equilibrium composition ratio, R = (φ1/φ2)/(v1/v2), is obtained through use of the customary expressions for the free energy of polymer solutions:

Here subscripts 1, 2, and 3 refer to the two liquids and the polymer, respectively, χ is a free energy parameter, l is the ratio V1/V2 of the molar volumes of the two liquids, φ and v represent the volume fraction in the ternary and binary phases, respectively, and ϵ is an auxiliary variable relating φ and v for the two liquid components. Certain consequences of the equilibrium composition relationship are examined, and there are suggested possible applications to diffusion, light scattering, and solubility. The results of analysis of the two phases formed when crosslinked natural rubber equilibrates with the mixed solvent pairs: benzene–nitromethane and m‐xylene–nitromethane confirm the form of the equilibrium composition relationship, and the values for the free energy parameters required to represent the data for these ternary systems appear to be reasonable.
Studies in chain transfer. III. Determination of chain transfer coefficients from catalyzed polymerization data
Authors: Palit Santi R. , Nandi U. S. , Saha N. G.
Published: April 2003

Based on a general equation correlating DP and rate for catalyzed polymerization in the presence of solvents, an experimental method has been devised for determining all three transfer coefficients, viz. monomer transfer (CM), solvent transfer (CS), and catalyst transfer (CI), in a simple and straightforward way. Three types of methods are possible for solvent transfer determination: (1) by determining the slope of

at constant 1 (catalyst): M (monomer) ratio; (2) by determining the intercept of

at constant S/M; and (3) by direct use of the general equation, especially using a catalyst whose CI is known to be zero. It has been further shown that the existing method (slope of 1/P versus S/M) in uncatalyzed polymerization would give correct results for all solvents only over the range in which the rate of uncatalyzed polymerization is proportional to the square of monomer concentration. It has also been pointed out that, in systems in which the more usual rate equation, RP = KP (ki/kt)1/2I1/2M3/2 is valid, the slope of 1/P versus S/M (at constant I/M) would give correct CS values for catalyzed polymerization also.