Southern Railway reported yesterday record profits for the second quarter and first six months of 1978, after which directors of the Washington-based transportation company voted an 11 percent increase in quarterly dividends.

Martin Marietta Corp. and Fairchild Industries, two Montgomery County industrial firms with significant aerospace operations, also posted record profits and sales. Baltimore Gas & Electric Co. reported higher earnings but the utility said petitions soon would be filed with Marylands public service commission, seeking higher rates.

Southern's president, Stanley Crane, said freight business rebounded sharply in the second quarter and contributed to record profits of $44.3 million ($2.94 a share) compared with $37.7 million ($2.51) in the same period a year ago, a gain of more than 17 percent.

Operating revenues jumped nearly 11 percent in the quarter to a record $336 million. Eleven of 12 commodity groupings showed increased business for Southern in the quarter, ranging from 2.6 percent for chemicals to 32.5 percent for farm products.

In the first half, Southern earned a record $73 million ($4.83 a share), up 12 percent from $65 million ($4.33) last year. Revenues climbed 8 percent to $615 million.

Directors increased the railroad's dividend rate by 7 cents a share to 72 cents, starting with a quarterly distribution on Sept. 15 to owners of record Aug. 15. Crane said freight carloadings continued strong during July and show "no signs of diminishing." He also said Southern continues to review a possible acquisition of the Illinois Central Gulf Railroad.

Martin marietta Corp., of Bethesda, reported record second-quarter profits of $37 million ($1.54 a share) compared with $31 million ($1.31) in the same period of 1977. Sales rose $446 million from $371 million for the diversified aerospace, chemicals, aluminum and construction materials firm.

First-half profits also were at a record level: $54.7 million ($2.29 a share) vs. $53 million ($2.24). Sales rose to $794 million from $680 million.

The 1977 first-half included cents a share from non-recurring income - an erospace fee payment for performance "excellence" and a gain from a debenture transaction.

Fairchild Industries, of Germantown, said second-quarter profits rose substantially to $5.5 million ($1.16 a share) compared with $1.7 million (37 cents) in the same period last year - the ninth consecutive quarter of sharply higher profits. Sales rose to $130 million from $95.5 million.

In the first six months, the aerospace and communications company earned $11.3 million ($2.38 a share) on sales of $251 million compared with profits of $2.9 million (63 cents) and sales of $184 million in the 1977 period.

Fairchild officials attributed the continued gains to increased delivery and improved production efficiency at the Republic division, which is building A-10 close support fighters for the Air Force. Fairchild delivered 22 of the planes in the recent quarter bringing the first half total to 40 (up from 27 in the same period of 1977).

Baltimore Gas and Electric Co. reported yesterday first-half earnings of $67.9 million ($1.91 a share), up from $52.5 million ($1.49) a year ago.

Chairman Edward Utermohle said the company expects to file a rate increase application "in the next few months" seeking $30 million to $35 million in additional annual revenues.

Utermohle also said the company plans to spend $239 million on construction this year and $218 million in 1979. About two-thirds of those funds will be financed internally, he said.

For the 12 months ended June 30, the company reported earnings of $118 million ($3.28 a share) compared with $100 million ($2.83) the previous year. Revenues for the year were $882 million, up from $756 million. For the quarter, revenues were up to $448 million from $398 million.

The company said the increased earnings were a result of "higher service rates, combined with increases in sales." Total gas sales for the six months increased 7 percent over the comparable peiod a year ago, and electric sales increased 5.9 percent, the company said.

Equitable Bancorp. reported record earnings of $3.2 million (88 cents a share) for the second quarter, compared with $2.6 million (72 cents) for the second quarter of 1977.

Equitable, a Baltimore-based holding company for several banks including University National Bank, based in Rockville, and Columbian Bank and Trust Co., reported first-half earnings of $6 million ($1.65 a share) compared with $5 million ($1.37) a year ago.

Equitable recently announced plans to merge its two largest banking affiliates. The plan calls for Equitable Trusts Co. to acquire University National.

Mercantile Bankshares Corp: reported second-quarter earnings of $2.6 million (58 cents a share) compared with $2.5 million (54 cent) a year ago, an increase of 7 percent.

First-half earnings increased 11 percent, to $5.2 million ($1.15 a share) from $4.7 million ($1.04) a year ago.

Overnite Transportation Co. of Richmond reported its highest earnings of any quarter with earnings of $3.8 million ($1.18 a share) for the second quarter, a 12 percent increase over last year's $3.8 million ($1.05).

Six-month earnings were also a record, reaching $6.1 million ($1.91 a share) compared with $5.2 million ($1.63) a year ago. Revenue was a record for both periods - $50.2 million for the quarter and $94.1 million for the six months.

The company, now not unionized, said the Teamsters union will hold elections at the company of Aug. 2, 3 and 4.