9. Procedure for Residues Exceeding 5 %
9.1 This procedure is applicable to such materials as heavy crude oils, residuums, heavy fuel oils, and heavy gas oils.
9.2 When the carbon residue as obtained by the procedure described in Section 8 (using a 10-g sample) is in excess of 5 %, difficulties can be experienced due to boiling over of the sample. Trouble also can be encountered with samples of heavy products which are difficult to dehydrate.
9.3 For samples showing more than 5.0 and less than 15.0 % carbon residue by the procedure described in Section 8, repeat the test using a 5 more or less 0.5 g sample weighed to the nearest 5 mg. In event that a result greater than 15.0 % is obtained, repeat the test, reducing the sample size to 3 more or less 0.1 g, weighed to the nearest 5 mg.
9.4 If the sample boils over, reduce the sample size first to 5 g and then to 3 g as necessary to avoid the difficulty.
9.5 When the 3-g sample is used, it can be impossible to control the preignition and vapor burning times within the limits specified in 8.3. However, in such cases, the results shall be considered as valid.
