International Bank, a major Washington-based merchant bank, posted a 32 percent decline in second quarter earnings but a 43 percent increase in earnings for the first half of the year.

The company, which owns stakes in a variety of industrial, insurance, leasing, real estate and offshore banking entities, said it earned $3.7 million (28 cents a share) in the second quarter, compared to $5.1 million (40 cents) last year.

Revenues increased 2 percent in the period, to $5.7 million from $5.6 million. The earnings drop was attributed by the company to a strike at a plant owned by its manufacturing group.

For the first six months, International Bank said, earnings rose to $7.3 million (57 cents) from $5.1 million (40 cents), while revenues climbed 19 percent to $10.9 million from $9.1 million.

Smithfield Foods Inc., the Arlington company famous for its hams, said increased hog supplies and reduced interest costs gave it a profit of $737,000 (25 cents) in the first fiscal quarter ended July 31, compared with a $2.1 million loss a year earlier. Sales rose 4 percent to $136,157 from $131,020 in the quarter.

Federal Realty Investment Trust, a Chevy Chase-based REIT that specializes in ownership and operation of shopping centers, said its earnings rose 82 percent in the second quarter, to $1.2 million (21 cents) from $679,000 (16 cents) last year. Revenues rose 21 percent to $4.4 million from $3.7 million.

For the first six months of the year, the company said, earnings rose 89 percent to $2.6 million (46 cents) from $1.4 million (34 cents) on sales of $8.9 million, a 16 percent increase from 1982's $7.6 million revenues for the first six months.

Security National Corp., the parent of Security National Bank, said its earnings rose 14 percent to $819,000 (89 cents) in the second quarter from $718,000 (78 cents) a year ago. Six-month income rose 1 percent to $1.52 million from $1.5 million. The company's assets increased 22 percent to $190 million at June 30 from $155.67 million a year ago.

Biospherics Inc., a Rockville maker of environmental-protection testing equipment and other products, said it earned $9,932 (zero per share) in the second quarter, compared with a $44,948 loss a year ago. Sales in the quarter rose 6 percent to $1.3 million from $1.2 million.

For the six months ended June 30, the company earned $54,455 (1 cent), compared with a $92,993 loss a year ago, as revenues rose 6 percent to $2.5 million from $2.4 million.