Colorimetric determination of <I>n</I>-butyl mercaptan in hydrocarbon with cobalt naphthenate

Abstract

Cobalt (II) naphthenate produced a blood-red colored compound in several organic solvents with n-butyl mercaptan. Based on this reaction, colorimetric determination of n-butyl mercaptan in hydrocarbon was investigated. The absorption intensity was influenced by solvent. Ethyl ether was used in the present method.The calibration curve was prepared as follows. The n-heptane solution containing the n-butyl mercaptan, not more than 4×10-5 mol of mercaptan, was taken into a 50 ml volumetric flask. Until the solution was 5 ml, n-heptane was added. And 2 ml of 0.01M cobalt(II) naphthenate was mixed to the contents. Then the mixed solution was diluted to 50 ml with ethyl ether. After 120 minutes, the absorbance of mixed solution was measured at 500 nm against the reagent blank. Beer's law was not obeyed. The molar absorption coefficient was 1100 M-1cm-1 at 3×10-5 mol/50 ml. Both tert- and sec-butyl mercaptans did not react.