ISO 2049 Petroleum products - Determination of colour (ASTM scale)
8 Expression of results
Report as the colour of the sample, the designation of the glass producing a matching colour, for example: "7.5 colour".
If the colour of the sample is intermediate between those of two standard glasses, report the designation of the darker glass preceded by the letter "L", for example: "L7.5 colour".
Never report the colour of a sample as being darker than a given standard except those samples darker than 8, for which the designation "D8 colour" shall be given.
If the sample has been diluted with kerosine (4.2), report the colour of the mixture followed by the abbreviation "Dil", for example: "L7.5 Dil colour".
9 Precision
The following criteria shall be used for judging the acceptability of results (95 % confidence level) when using the reference sample containers.
NOTE 1 The precision was derived by an interlaboratory test programme using sample containers of the dimensions shown in figure 1. The changes that have been introduced into the dimensions for routine analysis, in order to align with those specified in other International Standards stipulating similar glassware, are not expected to change the precision values, although this has not been verified.
9.1 Repeatability
The differente between successive test results, obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the normal and correct operation of the test method, exceed 0.5 of a colour number only in one case in 20.
9.2 Reproducibility
The differente between two single and independent test results, obtained by different operators working in different laboratories on nominally identical test material would, in the normal and correct operation of the test method, exceed 1 colour number only in one case in 20.
10 Test report
The test report shall contain at least the following information:
a) a reference to this International Standard;
b) the type and complete identification of the product tested;
c) the results of the test (see clause 8);
d) any deviation, by agreement or otherwise, from the standard procedures specified;
e) the date of the test.
