United Nuclear Corp. of Falls Church said increased production of uranium was chiefly responsible for its 66 per cent gain in sales and 50 per cent rise in earnings for the first quarter.

For the period June 30, sales increased from $34.3 million a year ago to $57.1 million. Profits climbed from $4.33 million (71 cents a share) to $6.49 million ($1.02) the company said.

Fully diluted earnings per share amounted to 92 cents against 62 cents.

President Keith Cunningham said uranium mining at Church Rock, N. M., began a month ahead of schedule. Shipments to processing plants started early in August. He cautioned that earnings for the later part of the year could be depressed because executives will be tied up by the trial of the company's lawsuit against General Atomic, which is to begin next Month in Sante Fe.

Flow General, Inc., of McLean reported a 54 per cent increase in net income to $1.15 million (87 cents a share) for fiscal 1977 from $747,000 (66 cents) a year ago. Sales rose less than 5 per cent to $42.2 million from $40.4 million.

The company, which makes and sells biological, medical and broadcasting equipment, said its operations for the fiscal year ended June 30 included losses from discontinued operations of $96,000 (7 cents) against $87,000 (8 cents) last year.

Washington Homes, Inc., of Oxon Hill, a major suburban builder, said profits increased 3.3 per cent to $1.22 million (93 cents a share) on a sales boost of 33 per cent to $35.6 million.

For the fourth quarters, sales increased to $114.4 million from $92.2 million a year ago, but profits declined to $164,770 (12 cents) from $401,082 (30 cents).

United Consolidated Industries of Hanover, Md., reported an 11 per cent increase in sales and a 14 per cent gain in earnings for the second quarter. Sales were $4.69 million with profits of $70,363, according to the company's unaudited figures.

For the first six months of the year, through July 31, sales were up nearly 8 per cent to $8.69 million while profits climbed 20 per cent to $86,277.

Because of a reduction in the number of shares outstanding, earnings per share for the quarter amounted to 23 cents, compared to 18 cents the prior year. Earnings per share were for the half climbed from 20 cents to 29 cents.

An auto parts distributor with 15 branches between Connecticut and the Carolinas, the company said it has sold three jobber stores and a small ware house on Eastern Long Island and will reinvest the money in new operations elsewhere.