Dynalecton Corp., a McLean-based diversified technological firm, reported yesterday record earnings for the fourth quarter and the year.

Net earnings for the year ended Dec. 31 were $13.9 million ($1.62 a share), a 177 percent increase from $5 million (65 cents) in 1980. Revenues were $475 million compared with $442.6 million in 1980.

For the fourth quarter, net earnings were $4.8 million (56 cents), up 85 percent from $2.6 million (31 cents) in the comparable period of 1980. Revenues were $125.8 million for the 1981 quarter, compared with $125.1 million.

In addition, the firm's board of directors declared a dividend of 20 cents a share, a 100 percent increase over the previous year, payable April 5 to shareholders of record March 18.

Biospherics Inc., a Rockville-based diversified environmental research and development firm, yesterday reported 1981 earnings of $189,110 (10 cents) compared with $16,619 (one cent) for 1980.

For the fourth quarter, earnings were $87,855 (5 cents) compared with $34,801 (2 cents) last year. Revenues in 1981 were $1.8 million compared with $1.6 million.

The company said record high interest rates resulted in interest costs of more than $245,000, despite a 40 percent reduction of total debt.

In addition yesterday, the 15-year-old firm said it has reached an agreement with Union Carbide Corp. to give it sole ownership of patents and technology for the Phostrip process, which removes phosphorus from waste water. The firm said the Phostrip technology made a "significant contribution to profits in 1981 and is expected to be a major factor in growth and profits."

Baltimore Gas and Electric Co. reported earnings yesterday for January of $10.6 million (31 cents) compared with $14.1 million (43 cents) for the same month last year. For the 12 months ended Jan. 31, the company reported earnings of $119.7 million ($3.58) compared with $126.6 million ($3.91) for the comparable period last year.