Fresh Oils5 0.044~X11! (5)
Used Oils Buffer end point5 0.117 X (6)
where:
X = the average of the two test results.
16.1.2 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 following values only in one case in
twenty.
Fresh Oils5 0.141~X11! (7)
Used Oils Buffer end point5 0.44X (8)
where:
X = the average of the two test results.
16.2 Strong Acid Number:
16.2.1 Precision data have not been developed for strong
acid number because of its rare occurrence in sample analysis.
16.3 Bias—The procedures in this test method have no bias
because the acid values can be defined only in terms of the test
method.
Test Method B
17. Reagents
17.1 See Section 7.
17.2 Potassium Hydroxide Solution, Standard Alcoholic
(0.01 mol//L)—(Warning—See 7.7 and 7.8.) Add 0.56 g of
potassium hydroxide (KOH) to approximately 1 L of propan-
2-ol or weigh 1.122 6 0.02 g of 50 % KOH into 1 L of
propan-2-ol. Boil gently for 10 min to effect solution. Allow
the solution to stand protected from carbon dioxide (CO2) for
two days and then filter the supernatant liquid through a fine
sintered-glass funnel. Store the solution in a chemically resistant
bottle. Dispense in a manner such that the solution is
protected from atmospheric carbon dioxide (CO2) by means of
a guard tube containing soda lime or soda non-fibrous silicate
absorbents and such that it does not come into contact with
cork, rubber, or saponifiable stopcock grease. Standardize
frequently enough to detect concentration changes of 0.0005
mol/L by potentiometric titration of pipetted quantities of
potassium acid phthalate solution dissolved in CO2-free water.
17.3 Potassium Acid Phthalate (KHC8H4O4), primary
standard, dried—Place 10 to 20 g of primary standard potassium
acid phthalate (KHC8H4O4) of 100-mesh fineness, in a
weighing bottle at 120°C for 2 h. Stopper the container and
cool it in a dessicator.
17.4 Potassium Acid Phthalate (KHP) Solution
(0.01 mol ⁄L)—For a volumetric standard, weigh approximately
1.0 g and record the weight to the nearest 60.0001 g of
dried potassium acid phthalate primary standard (KHC8H4O4)
and make up to the mark with DI Type II water in a 500 mL
volumetric flask. Alternatively for a weight-based standard,
weigh the KHP and record the weight to the nearest 0.0001 g
and record the total amount of water and KHP to the nearest