This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
(Zinc fused and poured into water).
Tests. - Zinc is chiefly used for preparing hydrogen, and these impurities are tested by adding pure dilute hydrochloric or sulphuric acid to it and holding over it a piece of paper dipped in acetate of lead. If sulphur be present the paper is blackened. If the piece of paper be wetted with solution of nitrate of silver, a brown or black stain is produced if arsenic is present. On lighting the hydrogen and depressing a piece of porcelain on it, a black stain is produced if arsenic is present.