RUBEANIC ACID AND ITS DERIVATIVES AS COLORIMETRIC REAGENTS.  PART I. SPECTROPHOTOMETRIC DETERMINATION OF COBALT,  NICKEL, PALLADIUM, SILVER AND RUTHENIUM WITH RUBEANIC ACID

Methods for the spectrophotometric determination of cobalt, nickel and palladium in alcoholic pyridine solutions with rubeanic acid are described. Cobalt has been estimated in presence of copper, nickel and silver by employing potassium cyanide and thiourea as masking agents. An extraction procedure for palladium with isoamyl aIcohol, using disodium salt of ethylenedi amine tetra-acetic acid as sequestering agent, is also described. A method of estimating silver in aqueous medium at P_H 4,0-4.6 has been developed. The method for determining ruthenium, as reported by Ayres and Young (Anal. Chem. 1950, 22, 1281), has been modified and improved. The colour system in all cases more or Less obeys Beer's law and gives values of high sensitivity.