Osmium: From the Tetroxide Distillate through Sulphide and Ammonium Osmichloride (Roscoe 1913)

Osmium tetroxide in solution is thrown down as sulphide, turned into sodium osmichloride by chlorine and salt, and precipitated as ammonium osmichloride. Heating that salt in a covered crucible leaves spongy osmium. Result: spongy osmium; the densest known metal (sp. gr. 22.48 when crystalline). Heated in air it forms the poisonous tetroxide again. Source: Roscoe and Schorlemmer, A Treatise on Chemistry vol. 2 (1913), p. 1349. Not given: amounts and temperatures. Osmium tetroxide and chlorine are poison gases. Picture drawn by Youblob.