Potassium: Carbonised Cream of Tartar and Charcoal Distilled from an Iron Bottle (Brunner and Wöhler, Thorpe 1912)

Charring cream of tartar gives potash mixed finely with carbon. At white heat in an iron bottle the carbon takes the oxygen and potassium distils off as a vapour. Result: potassium metal. Straight from the carbon it holds an explosive compound that can detonate on the slightest friction, so it must be redistilled once or twice. Source: Thorpe, Dictionary of Applied Chemistry vol. 4 (1912), pp. 336-337, after Brunner and Wöhler (Pogg. Ann. 1825). Not given: amounts, temperature, how the vapour is condensed. Picture drawn by Youblob.