DIN EN ISO 6271:2016-05

DIN EN ISO 6271 specifies a spectrophotometric method for estimating the colour of clear liquids in terms of Pt-Co units. It is applicable to clear liquids having a colour characteristic similar to those of the platinum-cobalt colour scale specified in Annex A. For products with colours more intensively than the Pt-Co stock solution the ISO 4630 method is recommended. The spectrophotometric method provides a more precise way of measuring Pt-Co colour than a visual sample comparison by human eyes. The term 'Pt-Co colour' used here is preferred over the terms 'Hazen colour' and 'APHA colour'