摘要:

The effect of age, concentration, and temperature on the Young's modulus of acid and alkaline silica gels bas been measured by a compression method. For the range of concentrations used the Young's modulus is not independent of load. The modulus increases with age of the gel and with concentration. Hurd's criterion of the time of set (tilted rod method) has been evaluated in terms of absolute units. The effect of temperature on the elastic properties is different for acid and alkaline gels. The Young's modulus values for the former (pH 5.6) increase, while for the alkaline gel (pH 8.2) of the same silicate concentration the values decrease with increasing temperature. The modulus for the alkaline gel is higher than for the acid gel at the lower temperatures. A mechanism is suggested to explain these differences.

ISSN:1923-4287    

DOI:10.1139/cjr49b-080

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

Apparatus is described for the measurement of small amounts of scattered light, dissymmetry of radiation, depolarization, and very small refractive index differences. Methods of calibration are critically examined. Benzene was adopted as a turbidity standard. Measurements were made on fractionated polystyrene of known molecular weight and on bovine serum albumin solutions. Values of the reduced intensity for benzene were obtained:Degree and sources of error are discussed

ISSN:1923-4287    

DOI:10.1139/cjr49b-081

出版商:NRC Research Press    

年代:1949

数据来源: NRC

摘要:

A study of the alkaline hydrolysis of C14carboxyl-labeled ethyl benzoate has shown that the substitution of C14for C12changes the rate of hydrolysis of the ester. Ester molecules containing C14hydrolyze at a slower rate than normal ester molecules. The ratio of the hydrolysis rate constants at room temperature has been found to be 0.86 ± 0.016.

ISSN:1923-4287    

DOI:10.1139/cjr49b-082

出版商:NRC Research Press    

年代:1949

数据来源: NRC