ISO/R 849:1968
Withdrawn
A Withdrawn Standard is one, which is removed from sale, and its unique number can no longer be used. The Standard can be withdrawn and not replaced, or it can be withdrawn and replaced by a Standard with a different number.
Phosphoric acid for industrial use Determination of iron content 2,2'- Bipyridyl spectrophotometric method
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03-20-2019
English, French
10-01-1968
Applicable to products having Fe contents of more than 0.001 % (m/m). Preliminary hydrolysis of polyphophate acids by prolonged boiling in the presence of hydrochloric acid. Reduction of iron(III) by means of hydroxylammonium chloride. Formation of the iron(II)-2,2'-dipyridyl complex in the presence of ammonium acetate at pH of 3.1 and a temperature of 75 C (under the test conditions the phosphate ions do not interfere). Spectrophotometric measurement of the coloured complex at a wavelength of about 522 nm.
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