Designate the color of the acid layer by the number of
the nearest matching standard, following the number with a
plus or minus sign if the sample is darker or lighter,
respectively, than the standard. Disregard any difference in hue
and determine only whether the color of the acid layer is darker
or lighter than the color of the reference standard to which the
sample most nearly corresponds. If the hue of the acid color is
different from the hue of the reference color standard, record
the color number followed by (X). Thus “No. 4 − (X)” means
that the acid wash test color is slightly lighter than No. 4 color
standard and that the hue of the No. 4 color standard is not the
same as the hue of the acid layer.
12.4 Dispose of the acid and hydrocarbon properly before
cleaning the container. Clean the test container by flushing
thoroughly with water (tap grade or better) until traces of acid
have been removed. The test container must be completely dry