Coulometric assay of the primary standards potassium dichromate and ammonium hexanitratocerate.
The high-precision coulometric titration apparatus of Eckfeldt and Shaffer (Leeds & Northrup Company) has been used for the precision assay of two primary standard materials for oxidation-reduction work. The purity found for NBS 136b Potassium Dichromate. 99.975 %, standard deviation 0.002 %, checks the earlier value of Marinenko and Taylor. Ammonium hexanitratocerate, if low in thorium, is also an excellent primary standard, two recent commercial preparations having purities of 99.972 and 99.984%, a higher standard deviation, 0.005 %, reflecting a minor difficulty in end-point detection caused by platinum oxide formation on the indicating electrodes.
Knoeck
J
J
Department of Chemistry, Iowa State University, Ames, Iowa 50010, U.S.A.
Diehl
H
H