An investigation of the freezing of water in capillaries

Abstract

In order to isolate the factors governing the freezing point of cloud and precipitation elements, experiments have been made to measure the effects of physical dimension and of certain ions in solution upon the freezing temperature of water in glass capillaries. The results of these experiments indicate that the freezing point of water in capillaries is independent of the volume or of the interface area, and that the radius of the capillary tubing is the only physical dimension that affects the freezing point of water contained in it. The amount of supercooling necessary to induce freezing can be either increased or diminished by the addition of certain ions in solution. The magnitude and sign of the change in freezing point are functions of the type of ions in solution, the molar concentration of the ions, and the capillary radius.

Freezing characteristics of rain water drops with different solutes and their implication on anomalous ice crystal concentrations in clouds

“…No explanation has been offered for the features noticed. Various views have been put forward by investigators in an attempt to explain the results obtained by them in similar contexts (Mason, 1954;Hosler & Hosler, 1955;DePena, et al, 1962)…”

“…(1) the anomaly has been particularly noticed in maritime clouds (Mossop, 1968), (2) even as early as in 1949, definite evidence of freezing in relatively warm maritime clouds was pointed out (Coons et al, 1949), (3) though the results of experiments reported so far on the effects of soluble salts on the freezing temperatures of drops have not been definitive (Lafargue, 1950;Mason, 1954;Hosler & Hosler, 1955;Hoffer, 1961;DePena et al, 1962& Pruppacher, 1963, the fact that soluble salts do influence freezing has not been ruled out, and (4) conditions simulated for ice nucleation in the conventional type of equipment used for measuring ice nucleus concentration could be different from those actually obtaining in natural clouds to take fully into account of the effect of the soluble salts present in the cloud air on the iceforming ability of the non-soluble nuclei contained therein.…”

Nucleation Behaviour of Iodide and Iodate Systems in the Presence of soluble salts

“…It may be noted that, according to Weyl (1951), a liquid surface consists of the most polarizable ions because polarizability permits an adjustment of the force-fields of the surface ions and, as a result, a lowering of the surface free energy. The implication of this postulate, as also discussedby Hosler (1951), is that a small supercooled drop can be made to crystallize by the addition of foreign molecules or ions that reduce the surface free energy of the drop. Since the amount of surface free energy is a function of the polarizability of the ions, the presence of more polarizable ions or molecules on the substrate will reduce the amount of supercooling necessary to form ice crystals.…”

“…That the presence of some soluble salts raises the freezing point of water drops is well known (Mason, 1954;Hosler and Hosler, 1955;Pruppacher, 1963;DePena et al, 1962;Sano and Uzu, 1965), though there has been no satisfactory explanation propounded about it. What is more important in the context of weather modification is to exploit this effect of the soluble salts for developing suitable mixes which can be used for producing efficient ice-forming nuclei.…”

Supercooling of Water

“…Hosler and Hosler (1955) used a variety of sizes of capillary tubes and found that, even when the capillaries had an diameter of only 0.2 mm, the lowest temperature they could reach with water samples was -33 C, at which point heterogeneous nucleation occurred. Most workers who use differential scanning calorimeters (DSC) use water as a control at one time or another.…”