Dip paper in a strong decoction of Brazil wood and dry it. Then dip the paper in it and dry it in the air. From the petals of violet-dahlias, as cabbage paper. This is merely paper stained with the juice of the berries. Its blue color is changed to red by acids, and to green by alkalies.
Chlorine has the same effect.
More color may be extracted from the litmus by hot water, but the liquid will require to be concentrated by evaporation. As the last, adding to the strained infusion few drops of nitric acid, or of pure acetic acid. It is not, like turmeric paper, affected by boracic acid. This is merely paper imbued with starch paste. Cotton cord is sometimes used instead of paper.