摘要:

It has been shown that relative humidity exerts a definite effect on the physical properties of a mass of asbestos fibre. A special apparatus has been devised in which a mass of fibre may be compressed in such a way that the volume, pressure and relative humidity of the sample are known at any time. The effect of sorbed water on asbestos is to increase the apparent density and to decrease compressibility and resiliency. It has been assumed that the major factor which controls these characteristics is the fact that sorption of water affects the surface in such manner that the slippage of the fibres over one another is facilitated. Since no fibre unit is experimentally obtainable in the case of asbestos, the fibre bundle must be considered and the stiffness of such a bundle depends on the ease of slippage of its components and hence on relative humidity. This fact is of prime importance in the testing of asbestos where humidity will exert a direct effect on the screen test.Cotton and wool fibres have been examined, and a definite effect of humidity demonstrated. Certain theoretical speculations in the case of cotton have been put forward.

ISSN:1923-4287    

DOI:10.1139/cjr34-001

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

Measurements have been carried out on the adsorption of hydrogen sulphide on a commercial sample of "activated alumina" by the dynamic and static methods. The adsorption is influenced by prior heating of the alumina to various temperatures, being a maximum when the temperature of prior heating is 550 °C.

ISSN:1923-4287    

DOI:10.1139/cjr34-002

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

The penetration of aqueous sulphite solutions into differently shaped blocks of spruce wood has been investigated, the effect of the shape and type of wood, and of the presence of imprisoned air being determined. Measurements of the rates of diffusion of the constituents of calcium bisulphite solutions into pre-soaked blocks of wood showed that "free" sulphur dioxide diffused more readily than calcium bisulphite. Adsorption of sulphur dioxide and calcium bisulphite solutions by spruce wood was measured at 30° and 50 °C., and the influence of this factor on penetration was determined. The effect of penetration on delignification indicated the necessity of a satisfactory distribution of the lime salt at a low temperature to avoid localization of the lime during the pulping process.

ISSN:1923-4287    

DOI:10.1139/cjr34-003

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

The rate of penetration of water through heartwood, pressure and temperature remaining constant, shows an initial fairly rapid decrease followed by a gradual decrease to a constant rate. With unseasoned sapwood, the rate of penetration increases to a maximum, after which it slowly decreases. With seasoned sapwood the rate decreases with elapsed time. Pre-soaking for periods up to seven days does not affect the equilibrium rate of penetration. The initial rate is lower with pre-soaked than with air-dry wood. Pre-soaking does not hasten the attainment of an equilibrium rate. Rate of penetration is fairly constant for heartwood specimens of the same kind taken from the same transverse section of a tree. Unseasoned sapwood is more than 200 times as permeable as heartwood from the same tree. White spruce, black spruce and red pine heartwoods show about the same penetrability at low pressures. At higher pressures red pine becomes much more permeable than white spruce at the same pressure. The same is true of cedar, tamarack and balsam. Unseasoned sapwoods show increasing penetrability in the order hemlock, balsam, red pine, white spruce. Observed apparent penetration radially and tangentially through heartwood is less than 9% of that in the longitudinal direction. (Water actually penetrating was in no case greater than 1% of that penetrating longitudinally in the same time through a specimen of the same thickness.) In sap-wood the rate of radial and tangential penetration is less than 2% of that in the longitudinal direction. Tangential penetration of white spruce sapwood is probably greater than radial penetration. Rate of longitudinal penetration increases with decrease in thickness of specimen. A very great increase in rate is noted after the thickness becomes less than one fibre length. This is suggested as a method of obtaining an approximation to the average fibre length. Rate is not inversely proportional to thickness, but decreases more rapidly with increasing thickness owing to loss of pressure head in passing pit membranes. Rate of penetration increases with increase in pressure differential. The rate is proportional to pressure (or slightly greater) in white spruce. The rate increases much more rapidly than proportionately with balsam, tamarack, cedar and red pine. This is due to bulging of thin pit membranes and consequent enlargement of perforations. Magnitudes of pressure and back pressure have no effect on rate of penetration, or time to reach an equilibrium rate, if pressure differential remains constant. Penetrability is not altered permanently by the application of pressure. Rate of penetration increases with temperature. Temperatures above 70 °C. have a permanent effect on the penetrability. Intensive drying of wood increases its penetrability.Sucrose solutions cause a decrease in rate of penetration greater than that expected from viscosity considerations. Molar sodium hydroxide increases the permeability of heartwood specimens of greater than one fibre length, and decreases that of sapwood and very thin sections of heartwood. Molar hydrochloric acid decreases the rate of penetration through heartwood, but has little effect on that through sapwood. Gases penetrate seasoned heartwood and sapwood easily. Pre-soaked heartwood strongly resists penetration by gases. Short lengths of unseasoned or pre-soaked sapwood are fairly easily penetrated by gases. All the evidence points to the absence of any valve action on the part of pit membrane tori.A new theory has been advanced to account for the phenomena ordinarily ascribed to valve action, and also to explain those observations which could not be explained satisfactorily as due to torus valves.

ISSN:1923-4287    

DOI:10.1139/cjr34-004

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

It is shown that the estimation of nitrogen by the Kjeldahl method on a semi-micro scale is more sensitive to variations in procedure than the corresponding macro method.Several methods of preliminary reduction, recommended for certain types of compounds, have been found difficult to adapt to semi-micro work. A method of reduction, involving use of hydriodic acid and phosphorus, has been developed for many such compounds.

ISSN:1923-4287    

DOI:10.1139/cjr34-005

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

The results of a study of the competing abilities of certain weeds and crop plants are presented. Characteristics studied as possible indicators of competitive efficiency were development of assimilation surface, stomatal number, readiness and uniformity of seed germination and distribution and penetration of root systems.It is shown that success in competition depends on readiness and uniformity of germination under adverse moisture conditions, the ability to develop a large assimilation surface in the early seedling stage, the possession of a large number of stomata and a root system with a large mass of fibre close to the surface but with its main roots penetrating deeply.Cereal crops were classified in the order of competing ability as follows:— barley, rye, wheat and oats, flax.Brassica arvensisandAvena faluawere the most vigorous competitors among the weeds studied.

ISSN:1923-4287    

DOI:10.1139/cjr34-006

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

The following conclusions are drawn from a uniform, co-operative, crop sequence study at seven stations in western Canada,viz., Morden, Indian Head, Swift Current, Scott, Lethbridge, Olds and Vermilion, from 1928 to 1932, inclusive (a total of 28 station-years). Foot-rot damage of wheat is significantly reduced where wheat alternates with summerfallow in a two-year rotation, where it follows summerfallow in other rotations, alternates with oats in a two-year rotation, follows oats in a three-year rotation, follows sweet clover in a three-year rotation, or where wheat is sown late. It is increased where wheat follows wheat, barley, or western rye grass.

ISSN:1923-4287    

DOI:10.1139/cjr34-007

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

The crown and root tissue from 43,305 of 47,360 plants examined in this investigation yieldedHelminthosporium sativum, Fusarium culmorumand otherFusariumspp., either alone or in combination with these or other fungi and bacteria. It was the exception for any mature plant, the surface tissue of which was disinfected, to be free from fungi or bacteria. None of the various crop sequences or cultural practices used in this study appeared to significantly affect more than another the relative prevalence of eitherH.sativumorFusariumspp., as indicated by isolations from the crown tissue of wheat. However, as there was a marked tendency at certain stations each year forH.sativumorFusariumspp. to predominate, it was concluded that certain factors of the environment were more effective than the crop sequence in modifying the relative prevalence of the two fungi mentioned in the crown and root tissue of wheat plants.

ISSN:1923-4287    

DOI:10.1139/cjr34-008

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

Data are given concerning the appearance ofCytosporaspp. on 15 species of shrubs and trees following a light ground fire near D'Arcy, B.C. On 11 of the hosts was found a species ofCytospora, which is herein described under the name,C.pulcherrima. On three of the hosts was found an undeterminedCytosporawith larger spores and darker, less delicate tendrils. On the one coniferous host present, Douglas fir, the only fungus present was determined asC.friesiiSacc.The taxonomic importance of the study rests on the range of species of infected hosts which revealed a width hitherto unknown or at least unreported for aCytospora.

ISSN:1923-4287    

DOI:10.1139/cjr34-009

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

The variation of the surface tension of carbon tetrachloride with temperature has been determined with considerable accuracy between + 12 °C. and − 10 °C.

ISSN:1923-4287    

DOI:10.1139/cjr34-010

出版商:NRC Research Press    

年代:1934

数据来源: NRC