To prepare ordinary litmus paper, powder 1 oz. of litmus and boil it with 4 oz. of water, filter, and wash the residue with a little hot water, adding this to the filtrate. If blue litmus paper is required, cut blotting-paper into strips, dip them in the solution, and hang up to dry. If red litmus paper is required, add one or two drops of nitric acid (just sufficient to change the colour of the solution to red and no more) and dip unsized paper in this. For careful work the litmus must be purified before using. To make turmeric paper, treat loz. of powdered turmeric with 4 oz. of warm methylated spirit. Allow this to stand for a few hours, when it should he filtered; blotting-paper should then be dipped in the solution and allowed to dry.