For comparison, the corresponding asphaltenes separated by straight-chain pentane contained: C, 78.3; H, 7.9; N, 1.3; S, 11.8 wto/
The following methods were applied to upgrade the 'naphtha': (1) refining in a glass laboratory fractionation still; the bad odour was eliminated by removing the material boiling up to 60ยฐC from the 'naphtha'; (2) acid washing with 90% H,SO,, which caused a loss of 4 wt Y0 of the total 'naphtha', but removed bad odour and coloured materials; (3) base wash with 30"/, aq. KOH, which caused a 2% weight loss, but contributed to the removal of undesirable materials. Elemental analysis* before and after the acid-base wash gave the following results, which show a considerable improvement in terms of sulphur nitrogen removal. * Analysis by Alfred-Bernhardt Micro-Analytical Laboratories, West Germany) Letters to the Editor Composition (wt ':,,) C H N S Before acid-base wash 85.0 14.0 0.3 0.3 After acid-base wash 84.9 14.9 0.05 0.02 Treatment of the parent crude oil with the acid-base purified naphtha still resulted in considerable precipitation (20.6(X of total weight) of heavy constituents. REFERENCES I 2 Recent results obtained by us in cooperation with the CFP-Total