Selenium. Standard electrode potentials, Eo, V

Oxidation of a sulfur compound with concentrated nitric acid yields sulfuric acid or a sulfate, which can be tested with barium chloride.

TESTS FOR SULFUR

	CH2=CH2 or C2H5OC2H5		C		CO		CO+CO2

VI		IV				-II
Acid medium
SeO	1,1	HSeO	0,74	Se	-0,11	HSe
Alkaline medium
SeO	0,03	SeO	-0,36	Se	-0,67	Se

[i] An azeotrope (pronounced /əˈzi.ətroʊp/ ə-ZEE-ə-trope) is a mixture of two or more liquids in such a ratio that its composition cannot be changed by simple distillation. This occurs because, when an azeotrope is boiled, the resulting vapor has the same ratio of constituents as the original mixture.

Because their composition is unchanged by distillation, azeotropes are also called (especially in older texts) constant boiling mixtures. The word azeotrope is derived from the Greek words ζέειν (boil) and τρόπος (change) combined with the prefix α- (no) to give the overall meaning, “no change on boiling.”

Over 9,000 azeotropic mixtures of pairs of compounds have been documented. Many azeotropes of three or more compounds are also known

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