Letter from Ernest Rutherford, FRS, 17 Wimslow Road, Withington, Manchester, to James Mackenzie Davidson Proposes an alternate process of separating thorium X; dissolving radiothorium and thorium in weak hydroloic acid, precipitating while hot with ammonia and transferring the whole of the hydroxide on filter paper to a strong flask. After leaving for a few days part of the thorium X should be dissolved out by the water. Suggests this is the superior method, as it offers a greater amount of thorium X without any intermediate chemical work. 12 March 1912