Business Notes DIVESTITURE

Mobil Oil, the largest U.S. firm still doing business in South Africa, had staunchly refused to join the more than 170 American companies, including Exxon and General Motors, that have closed their operations in that country because of its racial policies. But last week Mobil announced that it is also pulling out. The firm will sell its $400 million petroleum refining and marketing operations to General Mining Union Corp., a South African firm, for $155 million.

Mobil's decision was prompted by a change in U.S. tax law that was intended to drive American companies out of South Africa. Since last year U.S. companies can no longer deduct from their American tax bills the taxes they pay to the South African government. That change, which cost Mobil millions in 1988, finally broke its stubborn resolve to stay. Said Mobil Chairman Allen Murray: "This was a difficult decision because we continue to believe that our presence and our actions have contributed greatly to economic and social progress for nonwhites in South Africa."