Liquid gum is often put up for selling in penny bottles. For this purpose gum arabic, costing sixpence and upwards per pound, is suitable. Gum dextrine may be used, but a large quantity is required to yield a. good gum solution, and, moreover, it is usually dark coloured. A good gum may be made by dissolving l1b. of gum in 21b. of water; a poor gum by using 41b. of water. The former would yield 40oz. (or forty-six penny bottles), and the latter 70oz. (or seventy-six penny bottles), allowing for waste. The addition of a few drops of carbolic acid prevents the gum becoming mouldy. The gum should be covered with the water, and stirred till dissolved, no heat being required.