Mobil Corp., the nation's second-largest oil company, said yesterday that profits slipped 24 percent from a year earlier in the face of weakened demand and a worldwide oil glut.

Mobil, which is the first U.S. oil company to report first-quarter earnings, said net income declined to $640 million ($3.01 a share) from $846 million ($3.98) in the first quarter last year.

First-quarter revenues, however, rose to $17 billion, from $15 billion a year earlier.

Mobil's sale of its interest in Belridge Oil Co. in the first quarter of 1980, which resulted in an extraordinary gain of $459 million, was not included in the comparative results.

Failure of prices of chemical products to keep up with increasing costs, especially in Europe and Japan, slashed first-quarter profits of Dow Chemical Co. to 70 cents a share from the $1.27 a share earned in the exceptionally good first quarter of 1980.

Net income was $128.9 million on sales of $2.897 billiom, compared with $230.5 million a year ago on sales of $2.809 billion.

Minnesota Mining and Manufacturing Co. yesterday reported a 14.7 percent drop in first-quarter earnings and attributed the decline to unfavorable currency translations.

The diversified manufacturing company said net income in the latest quarter was $142.7 million ($1.22 a share) down from $167.3 million ($1.43) in the first quarter of 1980.

Sales rose 5.9 percent to $1.582 billion in the first quarter, from $1.494 billiom in the same 1980 period.

Uniroyal Inc., rebounding from a loss a year ago, yesterday reported first-quarter earnings of $7.6 million and cited increased efficiency in its domestic tire unit and wage and benefits reductions as reasons for the improvement.

Uniroyal's net income, which amounted to 24 cents a share, compared with a loss of $11.7 million (44 cents). Sales declined in the quarter ended March 19 to $541 million, from $580 million in the 1980 period.

Uniroyal, a major tire manufacturer with interests in chemicals, plastics and leisure products reported a $7.8 million loss in 1980 on sales of $2.3 billion as tire sagged with the automotive industry.

The Middlebury, Conn.-based company's tire and related products operations showed an operating profit of $13.7 million in the first quarter, compared with a $10.1 million loss in the same quarter a year ago.

The New York Times Co. said yesterday that acquisitions and growth in continuing operations boosted first-quarter earnings 11 percent this year to $12.1 million, the highest for any quarter in the company's history.

Profits for the quarter ended March 31 amounted to 98 cents a share of common stock. In the first three months of 1980, earnings were $10.9 million (90 cents a share).

Revenue in the latest quarter was $195.1 million, up 14 percent from the year-earlier $170.4 million.

The New York Times Co.'s operations include The New York Times and 18 other newspapers; radio and television broadcasting stations and cable televisions systems; Family Circle, Golf Digest and Tennis magazines; book publishing, and information and education services.

Republic Steel Corp. earnings in the first quarter rose to $2.01 a share from $1.28 a year ago as revenues climbed to $1.135 billiom from $1.002 billion.

Net income rose to $32.58 million from $20.64 million.

Physical steel shipments were up 3.6 percent from a year ago.