Some chemical properties of alum used in foods

B. T. Lim

Abstract

Twenty samples of alum used in food were collected and analysed qualitatively and quantitatively. All the alum samples were readily soluble in both water and 1% hydrochloric acid, sparingly soluble in 1% sodium hydroxide and insoluble in 95% ethanol. The aqueous solution (5%) of alum was acidic (pH 3.0-3.2). All the alum samples, when compared with pure potash alum, showed no significant difference (p > 0.05) in the contents of aluminium, potassium and sulphate, and weight loss on drying. Results showed that all the alum samples were aluminium potassium sulphate dodecahydrate or potash alum, and that their purity was at least 97%.

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