The New Student's Reference Work/Thallium

Thallium (thăl′lĭ-ŭm), a metal discovered in London in 1861 by the use of the spectrum. It is found in certain iron and copper pyrites, of which it forms about a four-thousandth part, and some in mica. It is generally obtained from the fine dust of pyrites burners. It resembles lead in appearance, is very soft, can be hammered into leaves, tarnishes quickly, gives a green color to a flame, and forms many compounds.