ISO 4274:1977
Withdrawn
A Withdrawn Standard is one, which is removed from sale, and its unique number can no longer be used. The Standard can be withdrawn and not replaced, or it can be withdrawn and replaced by a Standard with a different number.
Urea for industrial use Determination of biuret content Flame atomic absorption and photometric absorption methods
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02-15-2019
English, French
10-01-1977
Applicable to products having contents of equal to or more than 0.05 % (m/m) (with flame atomic absorption) or 0.1 % (m/m) (with fotometric absorption). Covers the formation of a complex between biuret and copper(II) sulphate in alkaline medium. Fixation of this complex on an anion exchange resin. Elution of Cu first with a potassium nitrate solution and then with a nitric acid solution. Flame atomic absorption: aspiration of the solution into an acetylene-air flame and measurement of the absorption of the 325-nm line emitted by a copper hollow-cathode lamp; or by photometric absorption: formation of a coloured complex between Cu and zinc dibenzyldithiocarbamate, extraction with carbon tetrachloride and measurement at a wavelength of about 435 nm. Has also been approved by the IUPAC.
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