Rhodium: Platinum Mother Liquor Worked through Lead, Barium Peroxide, Sulphur and Zinc (Deville and Debray, Roscoe 1913)

After the platinum is taken out, the liquor still holds the other platinum metals. Iron throws them down; lead and nitric acid strip palladium and copper; barium peroxide and aqua regia drive off the osmium; sulphur and zinc fusions purify the rhodium, which comes out as rose-red rhodammonium chloride. Result: rhodium metal, fused in the oxy-hydrogen flame. Source: Roscoe and Schorlemmer, A Treatise on Chemistry vol. 2 (1913), pp. 1328-1329, after Deville and Debray. The platinum mother liquor comes from the Heraeus wet process (Roscoe pp. 1378-1379). Osmium tetroxide vapour is highly poisonous. Picture drawn by Youblob.