Continuing high demand and increased prices contributed to a 27 percent year-to-year increase in second quarter net income for Aluminium Co. of America.

Alcoa, the nation's largest producer of aluminium, yesterday also announced a 5-cent divided increase to 50 cents a share. The new payout will be distributed Aug. 25 to shareholders of record Aug. 4.

Aluminium shipments were somewhat lower during the second quarter and first half than for the same periods a year ago because of buying by consumers hedging against a possible aluminium industry strike last year, Alcoa said.

Second-quarter net income was $74.8 million ($2.13 a share) on sales of $1 billion compared with 1977 second-quarter net income $58.9 million (1.70) on sales of $917.5 million.

First-half net income rose to $128.7 million ($3.66) from $107.8 million ($3.10) a year earlier as sales rose to $1.9 billion from 1.7 billion.

Wheeling-Pittsburgh Steel Corp., the nation's ninth largest producer, reported profits more than tripled in the second quarter from a year ago for the best quarterly showing in three years.

Second-quarter net income was $8.68 million ($2.11 a share) compared with $2.73 million (54 cents) in the same period last year Sales rose to $291,47 million from $262.61 million in 1977.

The firm also narrowed its first-half loss of $9.45 million on sales of $553.24 million, an improvement over the first half of 1977 when the net loss was $16.12 million on sales of $473.50 million.

Chairman and President Dennis Carney attributed the gain to modest price increases, increased volume, and elimination of the adverse financial effects of the coal strike and severe weather in the first quarter.

General Telephone and Electronics Corp. produced a 7 percent increase in profits to $149.4 million ($1.01 a share) in the second quarter from $134.6 million (94 cents) a year earlier. Sales rose to $2.15 billion from $1.88 billion.

Chairman Theodore Brophy attributed the earnings gains for both periods primarily to "sharply increased sales and net income from our products group." The gains also reflected continued growth in revenues and net income from the telephone operating group, he said.

KRAFT INC. reported increased earnings and sales for its second quarter and first half, with U.S., Canadian and international operations all contributing to the improvement for the leading maker of packaged foods and dairy products.

Second-quarter net income was $45.4 million ($1.62 a share) compared with $41.2 million ($1.47) a year earlier. Sales rose to $1.378 billion from $1,291 billion.

And Ralston Purina Co. report record sales and earnings for the third quarter and nine months ended June 30.

Third-quarter net earnings were $38.3 million (36 cents a share) on sales of $1.027 billion compared with $35.9 million (34 cents) on sales of $942.8 billion a year ago.

Ralston Purina said each of the firm's three business segments - consumer products, agricultural products, and retaurant - contributed to the earnings increase for the nine months.

Rockwell International Corp., a diversified aerospace firm, reported record earnings of $52.5 million for the third quarter of fiscal 1978, an increase of 42 percent over the $37 million earned in the same period of the previous year.

Per-share earnings rose to $1.50 from $1.07 last year. Sales for the third quarter were $1.52 billion compared with $1.47 billion.

Robert Anderson, president and chief executive officer, said four of the firm's five business contributed to the earnings performance. The fifth consumer operations, recorded earnings similar to those in the 1977 fiscal period.

Record earnings also were reported for the first nine months of fiscal 1978. Rockwell earned $136.1 million ($3.88 a share), up 33 percent from earnings of $102.5 million ($2.97) for the same nine months of fiscal 1977.

The four Rockwell divisions to which Anderson attributed the strong performances were aerospace, electronics, automotive and industrial businesses.

Southern Pacific Co. yesterday reported a 23 percent decline in second-quarter net income and blamed the poorer results on the severe freight car shortage during the spring.

The shortage occurred "when Southern Pacific freightcars "were not returned from eastern connections in the usual pattern" and the railroad incurred extra expenses "moving the empty cars thousands of miles to satisfy the requirements of our shippers," SP Chairman Benjamin Biaggini said in San Francisco.

But a U.S. magistrate there yesterday granted the Interstate Commerce Commission a preliminary injunction preventing Southern Pacific from keeping cars at holdpoints for more than 24 hours until July 31.

The ICC is seeking $4.4 million from the railroad for allegedly delaying trains and failing to return cars expeditiously to their owners during this nationwide freight car shortage.

The magistrate said SP had complied voluntarily with an ICC notice but "I feel some judicial restraint is in order."

SP's second-quarter net income was $30.9 million ($1.12 a share) compared with record earnings a year ago of $39.6 million ($1.47). Revenues rose by 8 percent to a record $592.22 million.

Seaboard Coast Line Industries reported second-quarter net income of $31.7 million ($2.17 a share), up from $28.5 million ($1.95) in the 1977 second quarter. Revenues rose to $491.9 million from $441.3 million.

B.F. Goodrich Co. reported lower second-quarter and first-half earnings than last year, but President John Ong said the company benefited last year from unusually high tire production rates following the 1976 strike.

Goodrich said second-quarter net income was $17.4 million ($1.15 a share) on sales of $628.3 million. In the same period last year, net income was $20.8 million ($1.38) on sales of $582.1 million.

Union Carbide Corp., the nation's second largest chemical producer, announced a 4.1 percent profit increase in the second quarter.

Earnings rose to $106.8 million ($1.65 a share) from $102.6 million ($1.62) in the second quarter of 1977. Sales were $1.98 billion compared with $1.78 billion.

Per-share earnings rerlected an increase to 64.6 million shares from 62.7 million average shares outstanding in 1977.

Another chemical firm, Monsanto Co. posted a small decline in second-quarter profits to $76.1 million ($2.09 a share) from $81.5 million ($2.21). Sales came to $1.18 billion, up slightly from last year's $1.12 billion.

Monsanto's six-month profits dipped to $211.8 million ($5.80) from $229.4 million dollars ($6.22). Revenues rose to $2.53 billion from $2.43 billion.

W.R. Grace and Co. announced a second-quarter profit of $51.5 million ($1.34) a share) compared with $48.7 million ($1.26) during the same year ago period.Revenues rose to $1.11 billion from $1.05 billion, the company said.

Celanese Corp., a diversified producer of petrochemicals, fibers, plastics and polymers, reported flat earnings for the second quarter.

Earnings for the quarter were $23 million, the same as last year's period, although per-share earnings moved up 7 cents to $1.60. For the half, the company earned $42 million ($2.85 a share) compared with $34 million ($2.27) a year earlier.

Revenues for the quarter were $665 million against $607 million a year earlier; for the half, Celanese revenues were $1.27 billion against $1.15 billion.

Burlington Industries Inc., the nation's leading manufacturer of textiles, reported that its fiscal third quarter profits dipped to $20.3 million (72 cents a share) from $25.5 million (90 cents) a year ago.

Sales for the period ended July 1 eased to $614.4 million from $621.9 million.

R.4. Reynolds. Industries Inc. and American Brands Inc., two of the nation's largest tobacco producers, reported improved second-quarter earnings based on sales increases.

R. J. Reynolds, the nation's No. 1 cigarette maker, reported record net income of $111.8 million for the quarter, up 11.8 percent from $100 million in the same period last year.

Earnings per share also set a record at $2.18 in the quarter, up 12.4 percent from $1.94 a year ago.

Rising revenues in the firm's tobacco sector and at Sea-Land Service, the world's largest containerized shipping company, offset a serious secline in energy sales.

American Brands reported second-quarter earnings of $42.54 million ($1.58 a share), up 3 percent from $41.5 million ($1.54) in the same quarter of 1977.

Second quarter sales this year were $1.2 million compared with $1.1 million last year.