Bis-substituted thiocarbamoyl disulfides (thiuram disulfides) were investigated as chromogenic reagents for the analysis of copper in trichloroacetic acid solutions. It was found that hydrogen peroxide speeded color development, increased color stability and enhanced color intensity in a trichloroacetic acid-alcohol matrix. In the presence of hydrogen peroxide, all copper complexes had molar absorptivities exceeding 30,000. Bis-pentamethylene thiocarbamoyl disulfide was selected as the best commerically available reagent of those investigated. The procedure is almost interference free, silver and mercury being the most serious interference. The sensitivity is 6 × 10−3micrograms/cm2.