M.Sc. (Chemistry) / The preparatIon of fine powders having large surface are as was carried out using the Hot Kerosene Drying Method (H.K.D.). In this method an emulsion containing An aqueous solution of a sought after cation is emulsified along with kerosene having a high boiling point (200+ C). The emulsion is then added to a given amount of the kerosene at a predetermined temperature above the boiling point of water, in a drop-wise fusion, during which the water con concerned in the emulsion rapidly evaporates resulting in the solid accumulating on the bottom of the flask. The powder is then separable from the kerosene using conventional means. Tungsten and iron-containing powders were each, made according to this method. The preliminary preparations were carried out with tungsten containing emulsions. In an attempt to produce an emulsion having the smallest internal phase diameter, w/o iron-containing emulsions prepared using different concentrations of the emulsifying agents and various kerosene-water ratios, were photographed microscopically under high magnification. Sedimentation rates and the presence of phase separation of the emulsions were recorded. In this manner an optimum emulsion with regard to particle size and stability was found. This emulsion composition was employed to prepare a series of emulsions with varying concentratiOns of the iron sulphate solution. Powders were prepared from these emulsions by subjecting them to the ".K.D. procedure. In another series of experiments the effect of the kerosene bath temperature on the quality of the poWders was studied. The surface areas of the solids were determined by using a dynamic method, and these could be directly related to the particle size of the powders for purposes of comparison...
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:10616 |
| Date | 14 April 2014 |
| Creators | Van Zyl, Adriaan |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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