bluuebunny/crossref_metadata_2025_split huggingface dataset:
Change in crystallinity upon heterogeneous acid hydrolysis of cellulose fibers
Authors: Hermans P. H. , Weidinger A. 
Published: April 2003

AbstractThe recently developed x‐ray method of crystallinity determination is applied to products of heterogeneous acid hydrolysis of cellulose fibers. Upon treatment of viscose rayon fibers with boiling 2.5 N sulfuric acid, the crystalline fraction is increased from 39 to 49% within half an hour, and remains constant upon prolonged treatment. Ramie does not show any change in percentage crystallinity when subjected to the same treatment. Its crystalline fraction is, however, transformed into cellulose IV. The observed changes in moisture regain of the hydrolyzed products are in line with the x‐ray results.
Specific refractivity‐temperature data for polyvinyl acetate and polybutyl acrylate
Authors: Wiley Richard H. , Brauer G. M. 
Published: April 2003

AbstractRefractive index‐temperature and volume‐temperature data for polyvinyl acetate and polybutyl acrylate have been determined and used to calculate the specific refractivity as a function of temperature by the Lorentz‐Lorentz and the Eyckman equations. The results show a variation of specific refractivity with temperature which exceeds experimental error. The variation is evident as an increase of specific refractivity with temperature above Tm and suggests experiments which will show the increase more clearly. A theoretical justification for the increase of specific refractivity with temperature in polymers is discussed.
Redox recipes. I. Reaction between ferrous iron and peroxides. General considerations
Authors: Medalia A. I. , Kolthoff I. M. 
Published: April 2003

AbstractVarious mechanisms which have been proposed for the reaction between ferrous iron and hydrogen peroxide are reviewed. Two of these mechanisms appear equally satisfactory on the basis of present evidence: that of Bray and Gorin, involving formation of tetravalent (ferryl) iron, and that of Haber and Weiss, involving formation ofhydroxyl and perhydroxyl radicals. Mechanisms involving these intermediates have been developed for the ferric iron‐catalyzed decomposition of hydrogen peroxide; the mechanism of Bray and Gorin appears satisfactory, while that of Haber and Weiss leads to certain inconsistencies. A mechanism with ferrous iron and hydroxyl and perhydroxyl radicals as intermediates is presented, which accounts for the experimental observations in the ferric iron‐catalyzed decomposition of hydrogen peroxide. The reaction between hydrogen peroxide and ferrous iron induces the reaction between hydrogen peroxide and various organic compounds; this induced reaction (termed a Fenton reaction) is a chain reaction which is initiated by the active intermediates (ferryl iron or hydroxyl radical) formed in the primary reaction. The determination of hydrogen peroxide by reaction with ferrous iron, if carried out in the presence of various organic compounds (termed promoters), gives incorrect results, due to induced oxidation of the promoters; other compounds, termed suppressors, reduce the extent of this induced oxidation of promoters. It appears that both types of compounds react with ferryl iron or hydroxyl radical to form radicals, which if formed from promoters, reduce ferric iron or hydrogen peroxide, while the radicals formed from suppressors oxidize ferrous iron. These considerations are of particular importance in the determination of organic hydroperoxides. The reaction between hydrogen peroxide or organic peroxides and ferrous iron can induce, or initiate, the polymerization of vinyl monomers; this is an example of redox polymerization, which is of considerable practical importance at present.
Polyelectrolytes. V. Osmotic pressures of poly‐4‐vinyl‐N‐n‐butylpyridonium bromide in ethanol at 25°
Authors: Strauss Ulrich P. , Fuoss Raymond M. 
Published: April 2003

AbstractThe osmotic pressures of two samples of poly‐4‐vinyl‐N‐n‐butylpyridonium bromide (average D. P. 730 and 1900) were measured in 93% ethanol in the concentration range 0.02‐0.20 g./100 cc. The osmotic pressures were higher than those of the corresponding parent polymers, due to partial dissociation of bromide ions. Because of the low dielectric constant ( ε′ = 28) of the solvent and the high concentration of positive charge in the polycations, however, a large fraction of the bromide ions (≥ 95%) were bound by electrostatic attraction to the cations and contributed neither to osmotic pressure nor to conductance. Unlike neutral polymers, the ratio (osmotic pressure over concentration) increases with dilution, due to increasing dissociation with dilution. Addition of an excess of a simple one‐one electrolyte (lithium bromide) almost completely suppressed the dissociation of the polysalt and gave osmotic pressures of the same order of magnitude as those of the neutral polymers. The resulting curves were linear, with a considerably smaller slope than for the parent polymer. Combining the results on osmotic pressure with conductance data, the transference numbers of the polycations were estimated to be 0.28 and 0.52 for degrees of polymerization 730 and 1900 respectively. The conductance of lithium bromide is decreased by the addition of these polyelectrolytes, possible due to the association of an excess of anions to the polycations under the influence of their electrostatic fields.
Compléments à l'étude de la statistique des chaînes moléculaires en solution diluée
Authors: Benoit H. , Sadron C. 
Published: April 2003

AbstractLe cas le plus simple pour calculer l'écart quadratique moyen entre les extrémités d'une chaǐne macromoléculaire est celui oùtoutes les rotations sont libres. Mais cette condition n'est généralement pas réalisée, aussi avons nous examiné dans cet article les résultats obtenus en introduisant une fonction de répartition symétrique pour les positions de chaque atome de la chaîne sur le cercle de base du cǒne de valence. Nous comparons les formules proposées jusqu'ici en représentant graphiquement leurs résultats (figs. 2 et 3). Cette comparaison montre que la formule de Kuhn et Taylor (8,9) est une approximation de celle que nous avons établié dans un article précédent (7) et a, de ce fait, un domaine de validité plus restreint. Ce domaine augmente avec le nombre des chaǐnons de la chaîne. En utilisant les fonctions de répartition proposées par Taylor nous représentons les valeurs de l'écart quadratique moyen en fonction de l'énergie d'interaction (figs. 6 et 7). Nous montrons ensuite que cette énergie d'interaction ne peut avoir la valeur calculée pour les vapeurs de carbures aliphatiques normaux mais est la somme de plusieurs termes et doit varier avec la nombre de chaǐnons et la température. Les formules établies permettent de prévoir deux aspects différents de la précipitation suivant qu'elle est effectuée par abaissement de la température ou adjonction d'un précipitant. Enfin, lorsque dans leurs rotations les atomes de la chaîne doivent passer par dessus des barrières de potentiel on peut prévoir des anomalies dans son comportement.
Thermodynamics of high‐polymer solutions. III. Swelling of cross‐linked rubber
Authors: Scott Robert L. , Magat Michael 
Published: April 2003

AbstractThe equilibrium swelling of the gum stocks of twelve different rubber vulcanizates has been measured in thirteen organic solvents. The results are in good agreement with the theory of Flory and Rehner. Values of the internal pressure (cohesive energy density) and the average molal volume between cross‐linkages Vc have been determined for the rubbers. The molal volume Vc is shown to agree closely with that obtained from measurement of the elastic modulus. An analysis of earlier data on the swelling of polybutadiene shows the number of cross‐linkages to be directly proportional to the sulfur content.
Photochemistry of proteins. VI. pH dependence of quantum yield and ultraviolet absorption spectrum of chymotrypsin
Authors: Finkelstein Paul , McLaren A. Douglas 
Published: April 2003

AbstractThe quantum yield of inactivation of chymotrypsin was found to be independent of variations in conditions of irradiation including light intensity, concentration of the irradiated solution, rate of stirring and the presence or absence of oxygen. The quantum yield for inactivation is at a minimum at the isoelectric point (pH 5.4). An explanation is offered for the variation of the quantum yield with pH in terms of an internal Franck‐Rabinowitch mechanism. The absorption spectra of the enzyme was also studied as a function of pH, as was that of an amino acid mixture whose composition corresponded to that of chymotrypsin. Evidence is presented for the existence of bound, un‐ionizing tyrosine in the native enzyme and of unbound tyrosine in alkali‐denatured enzyme. The significance of changes in the absorption spectra accompanying irradiation is discussed.
Pyrolysis of polyisobutene (vistanex), polyisoprene, polybutadiene, GR‐S, and polyethylene in a high vacuum
Authors: Madorsky Samuel L. , Straus Sidney , Thompson Dorothy , Williamson Laura 
Published: April 2003

AbstractSamples of polyisobutene, polyisoprene, polybutadiene, GR‐S, and polyethylene, weighing about 25 to 50 mg., were pyrolyzed in a vacuum of about 10−6mm. of mercury in a specially designed apparatus at temperatures ranging between 300 to 475°C. The volatile products of pyrolysis were separated into four fractions: (IV) gaseous, volatile at ‐196°; (IIIA) liquid, at ‐75°, (IIIB) liquid, at 25°; and (II) waxlike fraction, volatile at the temperature of pyrolysis. The gaseous fraction was analyzed in the mass spectrometer and was found to consist in all cases of CH4. The liquid fraction, IIIA, was analyzed similarly and was found to give a mass spectrum characteristic for any given polymer. A molecular weight determination of the waxlike fraction by the micro freezing point‐lowering method, showed it to vary from 543 to 739, depending on the polymer from which the fraction was obtained. It is shown that the method of pyrolytic fractionation of high molecular weight polymers, in conjunction with mass spectrometer analysis of the more volatile fractions, can serve as a means of identifying the polymers.
Polymers and copolymers of o‐acetoxystyrene and o‐hydroxystyrene
Authors: Marvel C. S. , Rao N. Shanmukha 
Published: April 2003

Abstracto‐Hydroxystyrene did not copolymerize with styrene and butadiene in GR‐S‐type systems. A terpolymer of these three monomers was obtained by copolymerizing o‐acetoxystyrene, styrene and butadiene in carbon tetrachloride solution by the action of stannic chloride followed by hydrolysis of the acetate groups in the polymer with dilute hydrochloric acid in dioxane solution. The polymer thus obtained did not improve the tack of GR‐S.
Determination of disappearance of bis‐isopropyl xanthogen (“dixie”) in synthetic rubber latex during polymerization
Authors: May D. R. , Kolthoff I. M. 
Published: April 2003

AbstractBis‐isopropyl xanthogen (“dixie”) is a poor promoter, but an effective modifier, in the GR‐S recipe, as was concluded from unreported intrinsic viscosity measurements. High molecular mercaptans are good promoters but very poor modifiers. In recipes containing mercaptans as promoters, dixie acts like a retarder until a conversion of 30% is attained. After this conversion the rate becomes normal. It is found that at a conversion of 30% most of the dixie has been dissipated. Bis‐isopropyl xanthogen can be determined polarographically. A procedure is given for the polarographic determination of dixie and the determination by amperometric titration of mercaptan when both dixie and mercaptan are present in a GR‐S latex. Disappearance curves of dixie and of mercaptans are given when both modifiers are present in the original charge.
Vitesse de polymérisation et de copolymérisation de l'acétate d'isopropényle
Authors: Hart R. , Smets G. 
Published: April 2003

AbstractEn présence de peroxyde de benzoyle, l'acétate d'isopropényle polymérise de la même facon que l'acétate d'allyle. Son comportement lors de la copolymérisation avec l'acétate de vinyle, le chlorure de vinyle et le méthacrylate de méthyle montre que ce monomère possède une réactivité générale semblable à celle de l'acétate de vinyle. Le caractère négatif de la double soudure est plus prononcé (−0.8). Ces copolymérisations sont caractérisées par un important transfert de chaîne, dû à la présence de l'acétate d'isopropényle. A l'égard du styrène, l'acétate d'isopropényle se comporte comme un solvant; il n'y a ni copolymérisation, ni transfert de chaîne.
Optische anisotropie und form von fadenmolekülen. II. Künstliche doppelbrechung
Authors: Stuart H. A. , Peterlin A. 
Published: April 2003

AbstractEs werden die Beziehungen für die elektrjsche, magnetische und die Strömungsdoppelbrechung von Fadenmolekülen in Lösung in Abhägigkeit vom Polymerisationsgrade angegeben. Ferner werden einige Möglichkeiten die Makro‐ und die Mikroform eines hochpolymeren Moleküls zu bestimmen und Verzweigungen zu erkennen, besprochen. Schliesslich wird durch Messungen der elektrischen Doppelbrechung am Dampf nachgewiesen, dass Paraffinketten lose Knäuel bilden.
Tetramethylthiuram disulfide vulcanization of extracted rubber. II. Structure of radioactive tetramethylthiuram disulfide
Authors: Craig David , Davidson W. L. , Juve A. E. , Geib I. G. 
Published: April 2003

Abstract(1) A study of the four sulfur atoms in tetramethylthiuram disulfide (TMTD) by radiosulfur techniques disclosed that these sulfur atoms are equivalent chemically. (2). The synthesis and reactions of radio‐TMTD were studied. (3) New reactions which were found for TMTD included those with the following substances: dimethylamine, n‐dodecyl mercaptan, ZnS, ZnO, zinc dust, S8*, and acetic acid. (4) Radiosulfur and the sulfur atoms in ZnDMDC do not undergo interchange, at least up to 150°.
Copolymerization of butadiene‐styrene by means of an oxygen, dodecyl mercaptan, and iron and cobalt pyrophosphates system
Authors: Marvel C. S. , Keplinger O. 
Published: April 2003

AbstractCopolymerization of butadiene‐styrene in soap emulsion can be initiated by the interaction of oxygen and mercaptans catalyzed by traces of ferrous pyrophosphate and cobalt salts. A recipe is described which effects conversions of 53% within 36 hours at −1°. The resulting rubber is very soluble in benzene and has an intrinsic viscosity in the range of 3.5–4.36.
Redox recipes. III. Use of various sugars at 0° and 30°C. in a cumene hydroperoxide–iron–sugar recipe
Authors: Kolthoff I. M. , Medalia A. I. , Youse Madolyn 
Published: April 2003

AbstractThe cumene hydroperoxide–iron–sugar recipe which gave attractive rates of conversion at 30°C. has been studied with several variations at 0°, using several sugars or sugarlike products. Dihydroxyacetone appears to be the most suitable reducing agent at 0°.
Copolymerization of phenylacetylene with vinylpyridine
Authors: Price Charles C. , Greene Charles E. 
Published: April 2003

AbstractExperiments on the copolymerization of phenylacetylene with 2‐vinylpyridine gave values for the copolymerization ratios, r1 = 4.0 ± 0.7 and r2 = 0.20 ± 0.05. Estimates of the copolymerization constants, Q = 0.3 and e = −0.6, from these experiments agree with those estimated from values of copolymerization constants recently reported by Doak from studies of copolymerization of phenylacetylene with methyl acrylate and acrylonitrile. The experiments reported herein support the report by Doak that phenylacetylene acts as a marked retarder, as well as a commoner.
Role of the semipermeable membrane in the osmotic molecular weight determination of cellulose acetate
Authors: Philipp Howard J. , Bjork Carold F. 
Published: April 2003

AbstractOsmotic pressure measurements are reported for solutions of unfractionated and fractionated cellulose acetate in acetone, using denitrated collodion, gel‐cellophane, and caustic‐treated cellophane as semipermeable membranes. Although techniques are employed that are presumably correct for the effect of diffusion, different osmotic pres‐ sures and hence apparent molecular weights are obtained with the three types of membranes. No correlation is found between osmotic pressure and either the permeability constant or the average pore diameter of the membranes. Measurements with a very low molecular weight cellulose acetate, the molecular weight of which is known from independent measurements, show that the rate of diffusion of small solute molecules through various membranes is not related to the rate of transfer of solvent molecules.It appears that the observed differences between membranes are caused by rapid diffusion of low molecular weight material at the beginning of the osmotic measurement, before even the first readings by a dynamic method can be taken. From measurements with the very low molecular weight cellulose acetate it is concluded that, in the case of cellulose acetate in acetone, correct osmotic molecular weights are obtained only with undried gel‐cellophane membranes, and that molecular weights determined with either the faster denitrated collodion or the slower caustic‐treated cellophane membranes are appreciably too high.
Rate of sorption of organic vapors by films of cellulose acetate
Authors: Mandelkern Leo , Long F. A. 
Published: April 2003

AbstractA detailed study has been made of the rate of take‐up of vapors of methylene chloride and acetone by thin films of cellulose acetate (37.9% acetyl) as a function of vapor pressure, film thickness, and temperature. It was found that the method of film preparation and conditioning greatly influenced the kinetics of the take‐up. Films, which were not completely dry, exhibit a much faster rate of take‐up than dry films. Dry films could he obtained by either long treatment in a vacuum oven, or by water leaching followed by vacuum drying for five days. In either case, identical kinetic results are obtained. The mercury cast films used in this work give reproducible results and show a much slower rate of take‐up than a comparable glass cast film.It was found that there was no fundamental difference in the rate of take‐up for the vapors of methylene chloride and acetone, although in the liquid state the former is a limited swelling agent, while the latter is a solvent. For both these yapors there is a characteristic pressure above which several anomalies appear, which make a complete quantitative explanation of the data rather difficult. The most important of these anomalies is that, if one plots the amount of vapor taken up as a function of time, an inversion of slope is observed. This inversian is very marked and is a function of film thickness. Another anomaly that appears is that the absolute amount of vapor sorbed for thinner films is greater than that for thicker films for an appreciable time interval. The effect of temperature is complex. Above the pressures where the inversion of a slope occurs, the rate is lower a t higher temperatures for a considerable range of the sorption. These effects cannot be explained on the basis of a generalized diffusion equation with the boundary conditions which have been considered so far, i.e., assuming that the outer film surface is always in equilibrium with the vapor.
Cationic polymerization of butadiene and copolymerization of butadiene and styrene
Authors: Marvel C. S. , Gilkey R. , Morgan C. R. , Noth J. F. , Rands R. D. , Young Charles H. 
Published: April 2003

Abstract

The cationic polymerization of butadiene with several Friedel‐Crafts catalysts has been described. Aluminum chloride and chlorosulfonic acid are active catalysts at −75°. The rate of polymerization at −75° is much faster than at the higher temperatures. Except for boron trifluoride etherate, which catalyzes the polymerization at −30°, the other catalysts (sulfuric acid, fuming sulfuric acid, stannic chloride, and boron trifluoride hydrate) produce appreciable amounts of polymer only at 0° or higher.
The effect of variables, such as catalyst concentration, catalyst solvent, dilution, reaction time, etc., differs with each individual catalyst. In some cases, results were not conclusive due to lack of reproducibility. It was found that the presence of moisture is mainly responsible for this lack of reproducibility. Traces of water promote the polymerization with stannic chloride or boron trifluoride etherate, but inhibit the polymerization when an ethyl bromide solution of aluminum chloride is used as catalyst.
Rubberlike polyhutadienes can be obtained with all catalysts except sulfuric and fuming sulfuric acids. However, the physical properties of these polymers show that the molecular weight is very low and that the polymer is not suitable as a rubber. Polymers ranging from viscous liquids to hard, brittle solids have also been obtained. In general, the solubility of the polymers is low. Approximately 60% of the butadiene enters the polymer chain by 1,4 addition.
The copolymerization of butadiene and styrene at −75° with an ethyl bromide solution of aluminum chloride has also been studied. At conversions between 20 and 30% a soluble, rubberlike copolymer having a low molecular weight is formed. An insoluble, brittle polymer is obtained a t higher conversions.
The soluble, cationic copolymer has a characteristic ultraviolet absorption curve which is different from that of GR‐S. It has a styrene content of approximately 50% by weight which demonstrates that the styrene is more active in cationic copolymerization than is butadiene.
Polyelectrolytes. VII. Viscosities of derivatives of poly‐2‐vinylpridine
Authors: Maclay William N. , Fuoss Raymond M. 
Published: April 2003

AbstractPolyelectrolytes were prepared by partial quaternization of poly‐2‐vinylpyridine (M = 45,000) with methyl bromide and butyl bromide. Viscosities of the former salt were measured in water and methanol; of the latter in water, methanol, ethanol and nitrobenzene. A new method of calibrating viscometers is described. Shear constants of the salts in aqueous solution were determined. The viscosity data conform to the equation:

Correlations between both structure of salt and dielectric constant of solvent, and the constants of the equation were found. Quaternary derivatives of poly‐2‐vinylpyridine are more rodlike than corresponding derivatives of poly‐4‐vinylpyridine.
Azo‐bis nitriles. II. Use of 2,2′‐azo‐bis‐isobutyronitrile as a catalyst for the polymerization of styrene
Authors: Overberger C. G. , Fram Paul , Alfrey Turner 
Published: April 2003

Abstract(1) The rate of polymerization catalyzed by 2,2′‐azo‐bis‐isobutyronitrile was found to be proportional to the square root of the catalyst concentration at 47.8° and 67.8° at a monomer concentration of 4 moles/liter. A square root dependence was also observed at 80.3° with 1‐azo‐bis‐cyclohexanecarbonitrile in pure monomer. At these temperatures, the number average degree of polymerization, assuming combination for the termination step, was inversely proportional to the square root of the catalyst concentration. These facts are additional evidence to support the unimolecular first‐order decomposition of the azo‐bis compound into radicals.(2) The monomer dependence on the over‐all rate was found to be 1.2, again at 68.2° this result is consistent with first‐order initiation and bimolecular termination.(3) The decomposition of 2,2′‐azo‐bis‐isobutyronitrile in pure styrene or in toluene and styrene is a unimolecular first‐order decomposition with a rate constant similar to that observed in pure toluene.