KCl Surface Research Articles

Growth of Potassium Chloride Crystals from Aqueous Solutions. I. The Effect of Lead Chloride

Single crystals of potassium chloride were grown from aqueous solutions under carefully controlled conditions of supersaturation, agitation, and impurity lead chloride concentration. The growth rate of the (100) face was determined. It was found that PbCl2 concentrations as low as 10−8 moles PbCl2/mole KCl decreased the rate of growth, and the retardation increased markedly with increasing PbCl2 concentration. The growth process changed from a layer type to a dendritic form over a small supersaturation range. Mass transfer rates of both KCl and PbCl2 from the solution to the crystal face were estimated and conditions delineated where each may be the rate-controlling step. A mechanism is proposed to account for the formation of crystal clusters on the surface of KCl at slow stirring rates.

Focusons in potassium chloride

The first experimental confirmation of the existence of focusons in alkali halides is reported. Energetic argon ion bombardment of KCl (100) surfaces produced preferential positive ion ejection along 〈111〉 and 〈112〉 directions. The results are interpreted in terms of an energy dependent hard sphere model.

Cool-flame combustion of hydrocarbons

The oxidation of three typical hydrocarbons (propane, cyclohexane, and n -heptane) in the cool-flame region has been studied, using a conventional static system, between 200° and 350°C with total pressures of 20 to 200 mm, and using either an uncoated vessel or one coated with boric oxide, potassium chloride, sodium hydroxide, or lead oxide. With an uncoated vessel the ease of formation of cool flames increases in the order: C 3 H 8 , C 6 H 12 , C 7 H 16 -KCl and particularly PbO coatings inhibit cool-flame production. Investigation of the oxidation products before and after the passage of a cool flame showed that, with cyclohexane and heptane, hydroperoxides-C 6 H 11 OOH and C 7 H 14 (OOH) 2 —are responsible for branching below 300°C leading to cool flames. The rates of oxidation under any conditions depend on the modes of reaction of the alkylperoxy radicals and hydroperoxides present in the system. These are probably more readily destroyed at KCl and PbO surfaces than at an acid-washed Pyrex surface.