Rubidium Chloride: Lepidolite Lithia Residue Parted with Platinic Chloride (Bunsen, Roscoe 1913)

Rubidium's double chloride with platinum is less soluble than potassium's. Precipitating with platinic chloride and boiling out the potassium salt again and again concentrates the rubidium; hydrogen then takes the platinum back. Result: about 125 g of rubidium chloride from 1 kg of residue, with 3–4 % potassium chloride and a little caesium chloride. The platinum is recovered. Source: Roscoe and Schorlemmer, A Treatise on Chemistry vol. 2 (1913), p. 367, after Bunsen. Unknown: the lepidolite residue; no blueprint extracts lithium from lepidolite yet. Picture drawn by Youblob.