摘要:

Various hemicellulose fractions were extracted from wheat straw holocellulose (extractive and pectin free) by successive treatments with cold and hot water, 0.5%, 1.0%, and 2.0% potassium hydroxide and were recovered by precipitation with alcohol. Approximately 25% of the holocellulose material was removed, one half being in the hot water soluble fraction. The original holocellulose, the extracted residue, and the recovered fractions were analyzed for pentosan, uronic acid anhydride, acetyl, methoxyl, and ash content. In general, the more soluble fractions had a higher uronic acid and methoxyl content; the less soluble had a higher pentosan content and a more negative rotation. Intrinsic viscosity measurements indicated that all fractions had a degree of polymerization of 25–30. Hydrolysis of the main fraction yieldedD-xylose,L-arabinose,D-glucose; in additionD-galactose was found in the water soluble fractions. Quantitative determinations of the sugars in the hydrolyzates showed thatD-xylose predominated, withL-arabinose,D-glucose, andD-galactose (when present) in progressively smaller amounts. On hydrolysis all fractions yielded an acid-resistant uronic acid complex that containedD-xylose and a uronic acid tentatively identified as monomethoxyl galacturonic acid.

ISSN:0008-4042    

DOI:10.1139/v51-015

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

A precision freezing point apparatus with platinum resistance thermometer was used to investigate the system hydrogen peroxide – water over the whole concentration range. The freezing point of the purest sample of hydrogen peroxide obtained by repeated fractional crystallizations of a large quantity of 99.6% pure solution was found to be −0.461°C; that of the dihydrate was −52.10°C. The two eutectics occur at concentrations of 45.2% and 61.2% H2O2and at temperatures of −52.4° and −56.5°C. respectively. Contrary to what has been reported previously, water and hydrogen peroxide do not form solid solutions together. This was proved conclusively by applying the technique of radioactive tracers to the 'wet residue' method of Schreinemakers.

ISSN:0008-4042    

DOI:10.1139/v51-016

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

Studies have been made of the change with time in the particulate number and rate of loss to surfaces of ammonium chloride smoke at various relative humidities ranging from 15% to 98%. The results are adequately described by the theory given previously with appropriate values for the loss and coagulation constants. The rate of disappearance of the smoke increased with increasing relative humidity, particularly above a value of about 60%. This circumstance is due to an increased loss rate from the system and not to increased coagulation. Though the possibility of 'protecting' an aerosol against coagulation is remote, it would appear possible to render certain aerosols more persistent in humid atmospheres by treatment affecting loss processes rather than coagulation.

ISSN:0008-4042    

DOI:10.1139/v51-017

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

A study was made of the alcohol–glycerol method of determining free lime in Portland cement and in mixtures of some aluminates and silicates of calcium.Strontium chloride is an effective accelerator. Calcium chloride is effective for mixtures of the pure silicates, but with Portland cement both it and calcium acetate give reduction of the total time required only at low concentrations and produce low values for free lime at higher concentrations of the salts. Lithium chloride produces acceleration, but magnesium chloride masks the presence of free lime. Addition of water in small amounts reduces the time required for the determination; larger amounts cause high values for free lime in the presence of tricalcium silicate.Lime heated to high temperatures becomes too inert to be determined without reactivation by suitable accelerators.The presence of 5:3 calcium aluminate and alumina interfere with the determination of free lime. The method is not satisfactory for underburnt lime–alumina–silica systems low in tricalcium silicate but is more suitable for such systems high in this compound. The higher values obtained with accelerators are probably more accurate than those obtained without accelerators. High precision may be attained with mixtures of dicalcium silicate, tricalcium silicate, and tricalcium aluminate.

ISSN:0008-4042    

DOI:10.1139/v51-018

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

The exchange reactions of iodide ion witho- andp-nitroiodobenzene in the temperature range about 170°–238°C were apparently second order with activation energies of approximately 29 and 33.5 kcal. per mole respectively. In the same temperature range the exchange of iodide ion with iodobenzene andm-nitroiodobenzene appeared to be first order reactions, with activation energies of approximately 25 kcal. per mole.

ISSN:0008-4042    

DOI:10.1139/v51-019

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

Both racemic forms oftrans2-chlorodecalin have been prepared and separated in pure form. The reaction between these chlorodecalins and ethylmagnesium bromide has been studied and two racemates oftrans2-ethyl decalin have been isolated. Some progress has been made in the preparation of the 9-chlorodecalins. A new method for convertingcisdecalin totransdecalin rapidly in high yield using tertiary butyl chloride and anhydrous aluminum chloride is indicated.

ISSN:0008-4042    

DOI:10.1139/v51-020

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

Several equations have been proposed that predict the shape of suspended particles when the viscosity of a suspension of known concentration is measured. These are not applicable to suspensions showing thixotropy, owing to the dependence of the measured viscosity on the shear rate used. However, by using viscosity values that have been extrapolated to infinite rate of shear, good agreement has been found between the predicted and measured shapes for particles in thixotropic systems, and the method appears to be suitable for submicroscopic particles. A scheme is also proposed for comparing the degree of thixotropy of different systems.

ISSN:0008-4042    

DOI:10.1139/v51-021

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

Some deuterium peroxide containing less than 0.3% ordinary hydrogen was produced both by the persulphate and the electric discharge methods. By means of fractional distillation, solutions of deuterium peroxide in deuterium oxide of various concentrations up to 90% were obtained, of which the following properties were measured: refractive index at 25°C, density, viscosity and surface tension at 0°C. and 20°C. Measurements of the last two properties were also extended to solutions of ordinary hydrogen peroxide. The physical constants of the two isotopic peroxides are compared and discussed. The density, viscosity and surface tension of supercooled heavy water at 0°C. were also measured for the first time.

ISSN:0008-4042    

DOI:10.1139/v51-022

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

Twenty-five pyrazolones were prepared by reacting mono- or disubstituted cyanoacetic esters with hydrazine, phenylhydrazine and semicarbazide. 4-Benzyl-3-amino-1-phenyl-5-pyrazolone has been synthesized and its properties have been compared with those of the corresponding 2-phenylpyrazolone derivative. The ultraviolet absorption spectra of several pyrazolones have been determined.

ISSN:0008-4042    

DOI:10.1139/v51-023

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

An investigation has been made of the relative rates of decarboxylation of two isotopic species of malonic acid, one containing only C12carbon atoms and the other containing a C13in a carboxyl position. Two effects were observed using malonic acid containing a normal abundance of C13—(1) a 3.3% faster rate of reaction for the molecule containing only C12carbon atoms; (2) a 2% greater probability of rupture of a C12–C12bond than a C12–C13bond in the molecule containing a C13carbon. The latter effect was found to be independent of temperature. The magnitude of the isotope effect is in reasonable agreement with theoretical predictions.

ISSN:0008-4042    

DOI:10.1139/v51-024

出版商:NRC Research Press    

年代:1951

数据来源: NRC