Bromatometry

The bromatometry is a redox titration , is oxidized at which a sample in an acid medium with a potassium bromate solution, which is reduced to bromide.

Bromatometry is a method of oxidimetry , whereby free bromine occurs at the end point, which causes the solution to turn pale yellow and any indicator that may be present is discolored. Mainly used for the determination of hydrazine and the cations As ³⁺ , Sb ³⁺ , Sn ²⁺ , Cu ⁺ and Tl ⁺ .

Example with iron (II) ions:

${\displaystyle \mathrm {6\ Fe^{\,2+}+BrO_{3}^{\,-}+6\ H^{\,+}\rightleftharpoons Br^{\,-}+6\ Fe^{\,3+}+3\ H_{2}O} }$

Only when there is no longer an oxidizable sample do bromide and bromate react with comproportionation to form elemental bromine .

${\displaystyle \mathrm {BrO_{3}^{\,-}+5\ Br^{\,-}+6\ H^{\,+}\rightleftharpoons 3\ Br_{2}+3\ H_{2}O} }$

Since bromine is able to destroy organic dyes , a dye such as methyl orange is added as an indicator . The discoloration indicates the end point of the reaction.

With bromatometry, semi-metals such as arsenic , copper , thallium , tin , iridium , tantalum , titanium , zirconium , bismuth and antimony are determined.

Bismuth (III) compounds cannot be titrated directly with potassium bromate, as +3 is already the most stable oxidation state for bismuth. Instead, the trivalent bismuth is reduced to metallic bismuth (0) with metallic copper. The Cu ⁺ ions formed are then titrated with potassium bromate.

Individual evidence

1. ^ ^{A b} Brockhaus ABC Chemie , VEB FA Brockhaus Verlag Leipzig 1965, p. 204.
2. ↑ Gerhard Schulze, Jürgen Simon, Jander Jahr Maßanalyse , 17th edition, de Gruyter, Berlin, 2009, p. 176.

literature

• Funk, Schär, analytical measurement technology: pH, redox, LF, O2; Measuring principle, application, devices, problem solving , Mainz: Aachen, 1996
• Kunze, Schwedt, Fundamentals of Qualitative and Quantitative Analysis , 5th ed .; Wiley-VCH: Weinheim, 2002
• Lappin, Redox Mechanisms in Inorganic Chemistry , Horwood: New York, 1994
• Otto, Analytische Chemie , 2nd edition (2000), Wiley-VCH: Weinheim

See also

• Bromometry , oxidimetry with bromine solution as oxidizing agent (when adding KBr ).