This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
The application just described (of acid nitrate) has been recommended also for chronic patches of psoriasis, and especially for such as occur along the forehead at the roots of the hair, but it should be used with great caution. The ointments of white and of red precipitate have a certain value for psoriasis of the face, or scalp, or hands, because they have no unpleasant color or smell, but they are seldom so efficacious as tarry preparations. The iodides, with iodide of potassium, are also recommended (Rochard, Lailler).