Studies on the Use of Coulometric and Amperometric Analysis

I. The coulometric determination of chromates and vanadates by means of electrolytically generated cuprous ion has been investigated. For samples of chromate larger than 170 micrograms, the error in the determination was less than 0.1 percent. The presence of oxygen has been shown to give a positive error of about 0.5 percent when determining vanadates. When oxygen was excluded, the error in determining 750 micrograms was less than 0.15 percent. II. The use of electrolytically generated argentic silver for the determination of manganous ion, cerous ion and arsenious acid has been investigated and has been shown to be impractical because of the slow rate of oxidation by the argentic silver. III. The determination of Bromine Numbers with electrolytically generated bromine has been investigated. For olefins which rapidly add bromine, the use of a 50 percent acetic acid solution of sodium bromide as the titration medium has been shown to give good results. A means has been proposed for the electrolytic determination of Bromine Numbers for slowly reacting olefins. IV. An amperometric method for determining the formal potential of the reaction 2 Cu+++7Br- = 2CuBr2-+Br3- has been investigated. The formal potential was found to be -.384 v. for solutions 0.017 formal in cupric ion, 0.44 formal in bromide ion, an 0.7 formal in sulfuric acid.