ISO 2750:1974

Urea for industrial use — Measurement of colour in Hazen units (platinum-cobalt scale) of a urea-formaldehyde solution

Lays down the principle of the visual comparison of the colour of a solution of the sample in formaldehyde, stabilized at a pH of 10 0.1, with that of colour standards. Expression of the results in terms of Hazen units. For routine control purposes, referring to ISO 2211. The method has also been approved by the IUPAC.