| Abstract: | Cobalt can be determined in the presence of other elements by chromatography followed by photometric scanning. The chromatographic solvent used is a mixture of acetone, n-butanol, hydrochloric acid and acetylacetone, and the cobalt spot is made visible by spraying with a solution of rubeanic acid. The filter paper is cut in strips which are scanned along their length either in a Beckman DU spectrophotometer or a Photovolt densitometer Mod. 525 at 422 mμ. The absorbance curves are plotted and the Co concentration is calculated from the area under the peaks. Chromatograms with 8 spots, each containing 0.4 — 2 μg Co, of which 4 are standards, are convenient. The coefficient of variation for the mean of a single chromatogram is 6 %. Alloys containing as little as 0.2 % Co can be analysed with an accuracy of 5 % or better. |
