11 Calculation
Calculate the acidity to the nearest 0,01, expressed as mg KOH/g of oil using the following equation:
where
V1 is the volume of alcoholic KOH solution (see 5.2) used to titrate the test portion, in ml;
V0 is the volume of alcoholic KOH solution (see 5.2) used for blank titration, in ml;
M is the molarity of alcoholic KOH solution (see 5.2);
m is the mass of the test portion used, in g.
12 Precision
12.1 Repeatability
The difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the values shown below only in one case in 20:
unused oils: 6 % of the mean value;
used oils: 12 % of the mean value.
NOTE The repeatability values for unused oils only apply where the result is significantly above the quantification limit, which has been established as 0,014 mg KOH/g oil.
12.2 Reproducibility
The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the values shown below only in one case in 20:
unused oils: 28 % of the mean value;
used oils: 35 % of the mean value.
NOTE Repeatability and reproducibility limits were established in accordance with ISO 5725 for used oil. Those for unused oil have been taken from ISO 6619.
13 Report
The test report shall contain at least the following information:
The type and identification of the product tested.
A reference to this International Standard.
The result of the test (see Clause 11) expressed to the nearest 0,01 mg KOH/g of oil.
Any deviation, by agreement or otherwise, from the procedure specified.
The date of the test.