Dart Drug Corp. yesterday reported that profits rose sharply.

Earnings were $15 million (85 cents a share) in the 10 months ended Jan. 31 compared with $1.3 million (71 cents) for the 12 months ended March 31, 1977. The Landover-based drugstore chain has changed its fiscal year from a period ended March 31 to one ended Jan. 31, conforming with the practice of most retail companies.

According to President Herbert H. Haft, sales totaled $153 million in the recent 10 months compared with $168 million during the previous full year.No fourth-quarter comparisons are possible because of the change in accounting periods, he added.

However, for January alone, Dart suffered a net loss of $163,000 on sales of $14 million. Haft said operations for January historically suffer from higher expenses in relation to sales in the post-holiday period.

"We are optimistic about our prospects in the current fiscal year," said Haft. he noted that Dart earned more in 10 months than the previous year, and said five large new drugstores have been opened and nine units remodeled in the 10-month period.

Dart also has opened four Crown Book discount stores in the metropolitan area, which are contributing "strong" sales, he said. The company recently opened two additional drugstores and completed remodeling two other units. Additional drug and book units are planned this year.

Union First National Bank of Washington yesterday reported a 19 percent increase in earnings for the first quarter of 1978. Net income was $1.16 million (51 cents a share) compared wiyh $971,419 (43 cents) in the same period last year. Assets rose by 24 percent to a record $600 million and deposits increased by 10 percent to a record $465 million.

Firemen's Insurance Co. of Washington earned $304,619 ($7.63 a share) in 1977 compared with $252,847 ($6.38) the previous year. The property insurance firm reported a premium volume of $2.4 million compared with $2.1 million in 1976.

Directors voted to increase Firemen's semiannual cash dividend rate to 85 cents a share from 70 cents.

Microdyne Corp., a Rockville manufacturer of telemetry and satellite television equipment, reported profits of $165,112 (14 cents a share) in the first quarter ended Jan. 29 compared with $52,814 (5 cents) a year earlier. Sales rose to $1.5 million from $845,874.

A company statement attributed the higher sales and profits to a 600 percent increase in sales of satellite TV receivers. A regular semiannual dividend of 5 cents a share will be paid June 16 to stockholders of record May19.