2. Sweeten approximately 150 mL of sample, following Steps 1 through 6 as described under Part
B: Acid Number, Mercaptan- and Thiophenol-Free Basis.
• If both Parts B and C were requested, the remaining sweetened sample from Part B, Step 7, should be used as the aliquot for Part C, and does not need further sweetening.
3. Measure, by graduated cylinder, approximately 135 mL of the sweetened, filtered sample into a
second 500-mL separatory funnel.
4. Add, by graduated cylinder, approximately 50 mL of 0.05-M sulfuric acid solution and shake
the solution with venting for approximately one minute.
5. Allow the layers to separate. Draw off and discard the lower acid layer.
6. Wash the hydrocarbon three times by shaking, with venting, for approximately one minute with
100-mL portions of water and discarding the water each time.
7. Filter the hydrocarbon through acid-free filter paper, discarding the first 10 mL of filtrate and collecting the remainder.
8. Proceed as described under Part A: Acid Number, As-Received Basis, using the sweetened, acid
washed, filtered sample and Titration Solvent 1.