Methods for the separation of platinum, palladium, rhodium, and iridium from one another and for their gravimetric determination

A method is described for the analytical separation of platinum from each or all of the three metals, palladium, rhodium, and iridium.It is based upon the complete precipitation of the hydrated dioxides of palladium, rhodium, and iridium in a boiling solution containing sodium bromate and having an acidity of pH 6.Two precipitations of the hydrated dioxides were found to be sufficient to effect the quantitative isolation of platinum.The separation of palladium from rhodium and iridium, by means of dimethyl- glyoxime, and its subsequent determination are also described.The procedure for the separation of rhodium from iridium by titanous chloride and for the determination of these two metals, given in detail in a previous publication from this laboratory, is discussed only briefly in this paper. CONTENTSPage I. Introduction 291 II.Materials used in the experiments 293 III.Separation of platinum from palladium, rhodium, and iridium 293 1.Method recommended for the separation of platinum from palladium, rhodium, and iridium, either collectively or singly 294 (a) Preparation of the solution 294 (6) Hydrolytic precipitation of palladium, rhodium, and iridium 294 IV. Discussion of the hydrolytic procedure 295 V. Determination of platinum 296 VI.Determination of palladium 298 VII.Determination of rhodium and of iridium 299 VIII.Experimental results on the separation of platinum from palladium, rhodium, and iridium 300 IX.Separation of palladium from rhodium and iridium 302 X. Separation of rhodium from iridium 303in the refining of platinum. 5In the analytical separation, a definite alkalinity was established by the addition of an excess of freshly prepared barium carbonate.In the refining operation, precipitation was made in a solution slightly alkaline with sodium bicarbonate to which sodium bromate was added.These researches of Wichers