EN ISO 6271:2015

European foreword
Foreword
1 Scope
2 Normative references
3 Principle
4 Apparatus and materials
5 Sampling
6 Procedure
7 Expression of results
8 Precision
9 Test report
Annex A (normative) - Platinum-cobalt colour standards
Bibliography

ISO 6271:2015 specifies a spectrophotometric method for estimating the colour of clear liquids in terms of platinum-cobalt units (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 intense than the Pt-Co stock solution the method specified in ISO 4630 applies.The spectrophotometric method provides a more precise way of measuring Pt-Co colour than a visual sample comparison by human eyes.NOTE The term "Pt-Co colour" used here is preferred over the terms "Hazen colour" and "APHA colour".