Spectrophotometric determinations of chromium in marine substances

Abstract

A general practical method for the determination of chromium in various marine substances has been developed using photometric measurements of diphenylcarbazide complex. Organic matter in the sample solution was decomposed by potassium permanganate, and chromate was reduced to chromium (III) by hydroxylamine in a dilute sulfuric acid solution. Chromium (III) was separated completely from iron, manganese and chloride etc. by several coprecipitations with aluminum hydroxide in the presence of hydroxylamine. The separated chromium (III) was oxidized to chromate with silver peroxide and colored complex formed. A half μg of chromium was easily determined in 10ml of the final solution. The method was applied to solid substances settled from sea water, to fine solid substances removed by high speed centrifuge from sea water, to a number of surface and deep sea water samples collected from the Northern North Pacific Ocean, to shallow sea deposits in Chesapeake and Tokyo Bays, to deep sea deposits in the Middle and South Pacific Ocean and to some Japanese seaweeds.