tellurium

Name tellurium
Symbol Te
Atomic Weight 127.60
Atomic Number 52
CAS ID 13494-80-9
Group Number 16
Group Name Chalcogen
Period Number 5
Origin of Name Latin, tellus = "earth."
Year Discovered 1783
Discovery Credits Discovered by Baron Franz Joseph Muller von Reichenstein at Subiu, Romania.
Class Semi-Metallic
Color Silvery Lustrous Gray
Standard State Solid at 77 F & 298 K
Description Silvery white, metallic looking in bulk but usually obtained as dark gray powder. Semi-metal. Burns in air or oxygen. Unaffected by water or HCl but dissolves in HNO3. Used in alloys to improve machine ability; chemicals, catalysts, electronics.

Diagnostic tests: 
Tellurium and tellurides are detected by heating the powdered mineral in a test tube with 5cc of concentrated H2SO4 acid. The presence of a reddish-violet color suggests Te. After cooling, addition of water will cause the color to disappear and a grayish black precipitate of tellurium will appear.

Open tube test of the powdered mineral oxidizes tellurium to TeO2 which passes up the tube as a white smoke and condenses near the heated part as a white coating. The coating can be fused into a globule which is yellow when hot and white when cold.

Closed tube test of the powdered mineral causes tellurium to volatize and condense on the hot glass as fused globules having a metallic luster. Minor amounts of white oxide may be produced along with the metallic globules.

On charcoal, the blowpipe produces a white sublimate near the assay somewhat resembling the test for antimony. The sublimate can be blasted with the blowpipe flame and imparts a pale greenish color to the flame.

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