Trace Analysis of Metals Using Naphthalene　Part I Spectrophotometric Determination of Cobalt after Extraction of Its Chinoform Complex with Molten Naphthalene

A new method is described for naphthalene extraction and spectrophotometric determination of trace cobalt with chinoform. The method is based on the formation of the colored complex which is extractable with molten naphthalene and on the dissolution of the extract in dimethylformamide. This solution follows Beer's law at 428 nm over the range of 3-43 μg of cobalt per 10 ml of dimethylformamide. The color of the complex is stable for 90 min. The various factors such as pH, amounts of reagent and naphthalene, digestion and shaking time are studied, and the molar absorptivity and relative standard deviation are estimated. The extraction of the complex into molten naphthalene is rapidly completed by contact with molten naphthalene or by slight shakin