Rapid Photometric Determination of Cobalt in Presence of Iron

General Photometric Microdetermination of Cobalt with Nitroso-R Salt

“…The method presented has been used successfully in the microdetermination of cobalt in a large number of soil samples. The sensitivity has been increased by a factor of 5, in the range 0 to 5 y of cobalt, over that of a previous procedure (5). The use of potassium brómate to oxidize the excess nitroso-R salt selectively, so as to leave the cobalt-nitroso-R salt chelate intact, is critically dependent upon the final nitric acid concentration.…”

Nature and Elimination of Interferences in Determination of Cobalt with Nitroso-R Salt

“…Willard and Kaufman (12) studied the absorption spectrum of cobalt-nitroso-R salt and concluded that 420 µ was the optimum wave length. Other investigators (1,6,7) have preferred to make measurements at 510, 525, or 550 µ.…”

“…Although some of these investigators have recognized and removed interfering ions, none have attempted to study the mechanism of such interferences as cerium, chromium, copper, vanadium, tin, manganese, nickel, and iron which form complexes with nitroso-R salt that may cause inaccuracies in the determination of cobalt (3, 5, 13). Some authors recommend the removal of these and other elements by ion exchange, electrolysis, or precipitation (2,4,6,11). Other investigators complex iron with phosphoric acid and remove Group II elements with hydrogen sulfide (3, 4, IS).…”