Iodisation of Lake Katwe salt, Kasese District

Abstract

The raw rock salt was analysed for chemical composition, refined and then iodised. The selected species determined are those known to hinder iodine retention in edible salt, namely; sulphates 20.7 % w/w, carbonates 31.7 % w/w, zinc 18 ± 4 ppm magnesium 945 ± 3 ppm, iron 168 ± 2 ppm and calcium 74 ± 3 ppm as ionic species were determined. The total amount of chloride was 1.54 % w/w.

Purification was by fractional crystallization, precipitation, and adsorption techniques. This yielded 85 % w/w salt as sodium chloride. The impurities were reduced markedly with sulphate 3.83 % w/w, carbonate 1.42 % w/w, zinc 4.22 ± 0.15 ppm, magnesium 7.64 ± 2 ppm, iron 7.40 ± 0.25 ppm and calcium 4.40 ± 0.3 ppm. Iodisation of the salt was done by addition of potassium iodate ( 0.378 g ) to the refined salt ( 200 g ) to give 100 ppm of iodine. Iodine retention was determined by iodometric titration conducted on the salt sample for two weeks. The quantity of iodine retained in the salt varied between 82.3 ± 3.8 ppm and 99.8 ± 9.0 ppm.. The salt can be profitably exploited if attention is focused to the manufacture of other products alongside salt e.g. fertilizers, carbonates, bicarbonate, stearate, and sulphate salts. This will subsidise on operation costs and reduce on the cost of the salt produced.