Investigations of the heavy metals test in the U. S. pharmacopoeia XII

Abstract A detailed study of the Heavy Metals Test in U. S. P. XII indicates that it is inaccurate and misleading for the following reasons: Appreciable amounts of heavy metals may be missed entirely; relatively large amounts of various metals may pass as equivalent to considerably smaller quantities of lead; light‐ or bright‐colored sulfides cannot be fairly matched against the darker lead compound; both the lighting and the vision of the observer are important factors in interpreting results; visual observations have been confirmed by tests with a photoelectric colorimeter. The possibilities of the presence of rarer metals, which would be indicated by the same test, and of other factors which might affect the accuracy of the test should not be ignored.