Abstract
The determination of phosphorus in high-purity chromium has been investigated and a procedure was recommended as follows.
The chromium metal was dissolved in aqua regia and perchloric acid and converted to chromic acid. It was diluted with water, and, after the addition of aluminum salt as a carrier, made ammoniac to precipitate phsophorus. 50 mg aluminum was sufficient (Fig. 4) and did not interfere with the color reaction (Table I). The phosphorus collected was determined colorimetrically with molybdenum blue method. The interference of chromium, tungsten, molybdenum, etc., has been criticizeá. The interfering elements such as silicon, arsenic, germanium, etc., was removed by adding dropwise hydrochloric acid and hydrobromic acid while heating the solution with perchloric acid. A large amount of iron interfered ( Table II) even after the reduction with sulfite. An analysis of electrolytic high-purity chromium from chromic acid or an analysis of com. electrolytic chromium of 99.99% purity from chromium-alum found 2.2 and 10.1ppm of phosphorus, respectively. The result of recovery tests was practically satisfiable.
