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Technical
Note Cyanide assay based on its novel reaction
with resorcinol and picric acid A
highly selective spectrophotometric assay of hydrocyanic acid and cyanide ions based on
their novel reaction with picric in the presence of resorcinol is described. Trace
concentrations of cyanides in water and hydrocyanic acid collected in dilute sodium
hydroxide solution are determined with a solution of 2 % sodium carbonate containing 110
µg/ml of resorcinol and 229 µg/ml of picric acid when a novel indophenol derivative of
2,6-dinitro-5-hydroxy-4- hydroxylamino-1-cyanobenzene is afforded. The formation of the
novel dye was proved by elemental and spectral analyses. The mixtures is heated at 100oC
for 30 min and, after cooling, the absorbance of the red-brown solution is read at 540 nm,
where the blank showed a minimum absorption. Detection limit of this method has been
evaluated to be below 0.01 µg/ml CN-. The color system obeys Beer’s law in
the range of 0.1 - 10 µg/ml CN-, in which a maximum molar absorptivity of 4.53
x 103 l/mole.cm has been determined. Cyanide in air, in cigarette smoke, and in waste
waters can directly be determined by this selective procedure, without its isolation. |
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