Thallium
in chemistry, a triad metallic element discovered by Crookes in 1861, and widely distributed as a constituent in iron and copper pyrites in blende, native sulphur, and in many kinds of ores; symbol Tl., at. wt. 203.64. It can be distilled with the sulphur by heating pyrites to a bright-red heat, then dissolving out the excess of sulphur by boiling with caustic soda, collecting and washing the sulphide of thallium, converting it into sulphate, and precipitating the thallium in the metallic state by THANET yards, at Woolwich 490 yards, at Graves end 800 yards, and 3 miles below, 1,290 yards. The basin of the Thames has an area of 5,400 square miles, and belongs entirely to the upper part of the Secondary and to the Tertiary formations. The depth of the river in the fair way above Greenwich to London Bridge is 12 to 13 feet, while its tides have a mean range of 17 feet and an extreme rise of 22 feet.
By means of numerous canals immediate access is given from its basin to those of all the great rivers of England. the action of pure metallic zinc. The Biskra. Here are in the solitude extenspongy metal is compressed, dried, and fused into a bright metallic button by heating under cyanide of potassium. It is a perfect metal, with high luster, not quite so white as silver, but free from the blue tinge of lead. It has a sp. gr. of 11.80-11.91, melts at 293°, is a very soft metal with less tenacity than lead, and almost devoid of elasticity. It communicates an intense green hue to a colorless flame, and its spectrum consists of one intensely brilliant and sharp green line, coinciding with the number 1442.6 on Kirchhoff's chart.