Bethlehem Steel Corp. yesterday reported a third-quarter net loss of $208.9 million, compared with net income of $77.3 million ($1.78 a share) in the comparable 1981 period.

And Mobil Corp., the nation's second-largest oil company, said yesterday its profit in the third quarter fell 36 percent from a year earlier.

Bethlehem Steel's loss came as raw production and shipments declined and steel production averaged only 37 percent of capacity, the company said.

Donald Trautlein, chairman and chief executive officer, said things are not expected to get any better:

"The economic recovery that we thought would begin in the fourth quarter has not yet materialized," he said. "We expect to sustain another sizable operating loss in the fourth quarter of 1982 and the outlook for Bethlehem for 1983 is uncertain."

Trautlein said Bethlehem's steelmaking facilities currently are operating at around 40 percent of capacity, and he added that he expects that level to be maintained through the fourth quarter.

"In the light of the continuing low level of business, we have again reduced our estimates of domestic steel shipments. We are now forecasting shipments in the low 60 million-ton range for this year and the middle 70 million-ton range for 1983," Trautlein said. The domestic steel industry shipped 87 million tons in 1981.

For the first nine months of 1982, Bethlehem had a net loss of $322.7 million, compared with a gain of $179.8 million ($4.12) last year.

Trautlein said the loss for the third quarter resulted mostly from the adverse impact of the economic recession and a pre-tax charge of $97 million for the restructuring of various operations.

Bethlehem continued to cut back production during the third quarter, the firm said. In order to decrease inventories, raw steel production in the third quarter was reduced to about 2 million tons, which is 33 percent and 52 percent lower than in the second quarter of 1982 and third quarter of 1981.

Mobil, like the other U.S.-based international oil concerns, was hit particularly hard by a slump in foreign profits. That is because crude prices were higher outside the United States while overseas demand for oil products was weaker.

Earlier this week, Exxon Corp. reported a 0.5 percent profit decline, Standard Oil Co. of California was down 13 percent and Gulf Oil Corp. was off 54 percent.

Mobil said it earned $323 million (78 cents), compared with $506 million ($1.19) in the third quarter last year. Revenue fell to $15.5 billion from $16.8 billion.

For the first nine months of the year, Mobil's profit was $959 million ($2.29), down 48 percent from the $1.85 billion ($4.34) reported for the same 1981 period. Revenue dropped to $47.7 billion from $50.5 billion.

General Foods Corp., citing gains in its coffee and processed meats businesses, said yesterday its fiscal second-quarter profit rose 15 1/2 percent from a year earlier although revenue fell 3.4 percent.

General Foods, based in White Plains, N.Y., is a leading maker of packaged foods. Its brands include Maxwell House and Sanka coffees, Post cereals, Jell-O desserts, Birds Eye frozen foods, Kool Aid powdered soft drinks, Good Seasons salad dressings and Oscar Mayer meats.

In the quarter ended Oct. 2, General Foods' earnings rose to $66.1 million ($1.34), from $57.2 million ($1.16) a year earlier. Revenue decreased to $2.01 billion from $2.08 billion.

For the first six months of its fiscal year, profit rose 20 percent to $127.6 million ($2.58), from $106.6 million ($2.15) in the comparable year-earlier period. Six-month revenue slipped 2 percent to $4.09 billion from $4.15 billion.

Earlier this month General Foods announced a proposal to acquire Entenmann's Inc., a bakery, for about $315 million. The acquisition is expected to be completed before year's end and should "result in little or no dilution of earnings, General Foods said.

Midland, Mich-based Dow Chemical Co yesterday reported third-quarter sales of $2.5 billion and profits pf $35 million (18 cents), down from $2.9 billion and $128 million (67 cents) last year.

For the first nine months, Dow reported sales of $8.1 billion and profits of $386 million ($2), down from $8.9 billion and $497 million ($2.65) for the same period in 1981.

"Economic conditions continue to hamper our business recovery on nearly a global scale," said Paul F. Orreffice, Dow president and chief economic officer.