The DuPont Co., the nation's largest chemical-producing firm, announced a second quarter net earnings rise of 26 per cent over last year to $161 million ($3.28 per share).

Last year, DuPont's second quarter net earnings were $128 million, or $2.60 per share.

Sales for the firm were $2.47 billion in the second quarter, up from $2.16 billion last year.

The company said the increase reflected continued strength in its chemicals, plastics and specialty products business.

RCA Corp. reported yesterday that second-quarter net income rose about 30 per cent over a year ago.

The media giat said net income was $70.1 million (92 cents a share) compared with $53.7 million (70 cents a share) in 1976. Sales rose to $1.43 billion from $1.32 billion.

For the first half, net income was $118.6 million, or $1.55 a share, versus $88 million, of $1.14 a share. Sales were $2.8 billion versus $2.58 billion.

TRW, Inc., yesterday announced record sales and earnings for the second quarter. Net earnings rose 12.4 per cent to $42.5 million ($1.33 per share) from $37.8 million ($1.18 per share) a year ago.

Sales for the Cleveland-based automotive and aircraft parts manufacturing company were $825.6 million, a rise from last year's second quarter of $743.8 million.

Celanese Corp. announced nearly flat second quarter net earnings of $23 million ($1.53 per share) compared to 1976's second quarter earnings of $23 million ($1.55 per share).

The company reported sales of $607 million, a 9 per cent rise over last year's $556 million.

Time Inc, profits for the second quarter and first half of 1977 were at record high levels due to substantial gains by its magazines, books and buildings materials operations, the company said.

Time's second-quarter income was $25.14 million ($1.24 per share), a 2 per cent increase from $50.1 million ($1 a share) in the second quarter of 1976.

Revenues increased 17 per cent to $311.23 million from $265.38 million in 1976.

Six-month net income was $40.1 million or $1.98 per share, 31 per cent higher than the $30.73 million or $1.53 per share earned in the first half of 1976.

Revenues were $579.18 million in the first six months, compared with $494.18 million in the first half of 1976.

Burlington Northern, Inc., the nation's largest railroad, reported a substantial increase in second quarter profits to $14.7 million (62 cents) recorded for the same period last year. Revenue for the period totaled $529.7 million compared to $459.5 million.

McGraw-Hill Inc., reported an increase in second quarter earnings to $10.2 million (41 cents a share) compared to $7.5 million (30 cents) for the same period a year ago. Revenues totaled $151.8 million, up from $134.6 million a year ago.

Philip Morris Inc., the nation's second-largest cigarette maker, announced second quarter net earnings of $85.1 million ($1.42 per share), compared to last year's profits of $67.2 million ($1.13 per share). Sales were reported as $2.5 million, up from $2 billion in the same period last year.

Kraft, Inc., reported second quarter profits of $41.2 million ($1.47 a share) compared to $36.05 million ($1.30) in the same period a year ago on sales of $1.3 billion compared to $1.23 billion a year ago.

Bank American Corp. parent corporation of the nation's largest bank, reported an increase in second quarter net earning of 15.4 per cent over the same period last year.

Consolidated second quarter net earnings after securities transactions were $93.0 million (64 cents a share) compared with $78.7 million (57 cents) in the same period of 1976.

Boise Cascade Corp. said its second quarter net income reached $32.6 million ($1.10 per share) compared with $27.6 million (94 cents) a year earlier.

Sales rose to $591 million from $509 million for the same period in 1976.