Paraffin Film Research Articles

Time dependence of heterogeneous nucleation

Freezing of supercooled water drops has been studied by a constant-temperature method to determine the dependence of heterogeneous nucleation on temperature and on the duration of supercooling. A polished metal surface, coated with a water repelling film of liquid paraffin, is used to support the rain-sized water drops being frozen. Complex and rather unexpected behavior was observed during initial freezing after sudden chilling. However, the latter part of the freezing process agrees with the equation developed from the probability considerations by Bigg and shows time dependence. The complex parts of the curves obtained during initial freezing can be explained by the recently discovered dependence of freezing temperature of supercooled drops on rate of cooling.

Dependence of Freezing Temperature of Supercooled Water Drops on Rate of Cooling

The dependence of the median freezing temperature of supercooled water drops on rate of cooling is studied over a wide range of cooling rates. A polished metal surface, coated with a water repelling film of liquid paraffin is used to support the water drops being frozen. Deeper supercooling is observed with higher cooling rates in the range 0.3 to 5.0 deg C min−1. However, for cooling rates greater than 5.0 C min−1 a reverse trend is indicated and the drops freeze at warmer temperatures. The importance of tins experimental result is discussed in the case of thunderstorm clouds with strong updrafts. A similar effect for sublimation nuclei tested in cold chambers has been noted by Schulz (1947) and by Smith and Heffernan (1954).

Methods of Evaluating the Chemotropic Response of Boll Weevils to Extracts of the Cotton Plant and Various Other Substances1

Two methods are described for testing the chemotropic response of the boll weevil, Anthonomus grandis Boheman, to various substances. In one method, solutions of pure chemicals or extracts of the cotton plant were applied to a feeding dish containing diet. In the other, plant parts were placed in a small container covered with a paraffin film to prevent contact of the test material by the insect. The behavior of the boll weevil in both assay methods is described and the applications of the methods are discussed. A solvent extraction of cotton plant parts and the chromatography of the extract are described. By the use of the diet method, several fractions attractive to the boll weevil were found.

Uses of sheet paraffin and plastic films in paper chromatography: spotting of large volumes on paper; elution; strip chromatography

A number of simple chromatographic applications are described in which sheet paraffin or other plastic film is used as an adhesive vapor barrier: 1.A funnel attached to a paraffin-enclosed narrow paper wick for spotting large volumes of sample solution as small spots of controlled size.2.A funnel for the elution of a spot and its reapplication to another paper in a single operation.3.A method for elution or chromatography which requires no jars or other rigid saturation chambers.

Hysteresis of contact angle of water on paraffin. Effect of surface roughness and of purity of paraffin

The experimental results show that when very thin films of purified paraffin were formed in vacuum by volatilization on smooth glass surfaces and water drops were placed upon them, the advancing and the receding contact angles were sensibly the same, 112°; that is, hysteresis effects did not exist on these very thin and very smooth surfaces. Measurable hysteresis effects from 5° to 35° were found for less smooth films, and coatings of appreciable thickness formed in vacuum, in nitrogen, or in air, whether from a melt or by volatilization. The magnitude of the hysteresis effects appeared to be closely associated with the microscopic roughness of the surfaces, the roughness adding to the magnitude of the advancing angle but subtracting from the receding angle to the same degree, so that the average angle remained the same for paraffin films of different roughnesses but of the same degree of purification. The average contact angle for purified paraffin was slightly larger than the average angle for unpurified paraffin.

The Study of the Structure of Tbin Film of Paraffin on Metallic Surface. (Repor No. 2)

The Study of the Structure of Tbin Film of Paraffin on Metallic Surface. (Repor No. 2)

RELATION OF CONTACTING SURFACE AND ANTICEPHALIN ACTIVITY TO THE MAINTENANCE OF THE FLUIDITY AND COAGULABILITY OF BLOOD

Abstract A review of the various factors in the blood that have to do with the promotion and the retardation of coagulation is presented. Circulating blood seems to have within and about itself all the factors required to delay or to promote coagulation. The stability of blood (i.e., its tendency to remain fluid) depends on the extent of the dominance of the anticoagulant (fluidity-inducing) group of factors over the coagulant (coagulation-promoting) group. Among the anticoagulant factors are the natural anticephalin activity of the plasma and the intact vascular endothelium; the latter is simulated by such contacting surfaces as collodion and paraffin films. Alterations in the stability of blood result from uncompensated increases or decreases in one or more of the anticoagulant or coagulant factors. The increased stability of hemophilic blood, due to an uncompensated excess of anticephalin activity, enables it to resist activation by cephalin or by contact with injured walls of blood vessels or with surfaces like glass. Blood obtained from normal individuals after severe hemorrhage has a decreased stability owing to an uncompensated diminution in anticephalin activity; such blood is readily clotted by cephalin and may not remain stable even when in contact with undamaged vascular endothelium or surfaces like collodion or paraffin.

Paraffin Films and Oil Dressings

Paraffin Films and Oil Dressings