thallium [Tl]

Introduction

From the Greek thallos meaning green twig or shoot, because of the color of its spectral lines. Discovered in 1861 by Sir William Crookes.

Occurrence

• sparsely but widely distributed
• by-product of producing sulfuric acid
• by-product of refining zinc or lead

Characteristics

• silvery-white metal
• resembles lead in its physical properties
• forms Tl+1
• toxic

Uses

• used chiefly in the form of compounds
• Tl-201 as thallous chloride (Tl+) is used in myocardial perfusion studies; 1/2 life of 72 hours
• photoelectric cells, semiconductors
• pesticides
• many traditional uses have been phased out because of its toxicity

Pathology

• alopecia most common manifestation of toxicity
• painful ascending neuropathy
• gastrointestinal symptoms

More general terms

• chemical element
• metal

Additional terms

• myocardial perfusion & viability scintigraphy
• periodic table
• Tl+