Platinum Sponge: Crude Platinum in Dilute Aqua Regia, Thrown Down with Ammonium Chloride (Heraeus, Roscoe 1913)

The wet process of the Heraeus works in Hanau: crude platinum is dissolved in dilute aqua regia, dried and heated to 125 °C, then the platinum alone is thrown down from the acid extract as ammonium platinichloride. Ignited, the salt leaves spongy platinum. Result: platinum sponge, and a mother liquor that still holds palladium, rhodium, ruthenium, osmium and iridium, for making rhodium. Source: Roscoe and Schorlemmer, A Treatise on Chemistry vol. 2 (1913), pp. 1373 and 1377-1379. Not given: amounts of ore, times, how the retorts are heated, ignition temperature. Aqua regia is a strong acid; mercury vapour is poisonous. Picture drawn by Youblob.