(Gr. thallos, green twig) Discovered by Crookes in 1861. Named after the green spectral line the element produces. Found in crooksite, lorandite, pyrites and hutchinsonite.
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metal, metallic luster, develops bluish-gray tint on exposure to air, reacts with water, soft, malleable, can be cut with a knife, 20 isotopes (191-210), elements and compounds are toxic, contact with skin is dangerous, suspected carcinogen
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thalium sulfate is an odorless and tasteless rodenticide and ant killer and has been banned in the US since 1975, infrared detectors, photocells, added to produce low melting glasses, had been used to treat skin infections (limited due to toxicity)