The second round of a dust-up between the Cincinnati AFL-CIO Labor Council and Thompson Hine & Flory, the law firm organizing a seminar for businesses titled ''How to Remain Union Free,'' was a lot quieter than the first.

Thursday morning, about a dozen union members picketed outside the Hyatt Regency downtown to protest resumption of the seminar that ended Feb. 8 when union protesters stormed the session in one of the hotel's banquet rooms. Thursday's picketing ended after a Hyatt official said the seminar was canceled.

Peter Newman of Thompson Hine & Flory said the seminar was canceled Wednesday after the union ran an ad in The Downtowner, including a Feb. 25 letter from the law firm announcing the rescheduling of the session. Mr. Newman said his firm has offered to complete the seminar for participating companies at its facilities.

Midland dividend hits 70 cents

Cincinnati-based Midland Co. has raised its annual dividend rate to 70 cents a share from 66 cents.

The first quarterly dividend of 17 1/2 cents a share will be payable April 10 to shareholders of record March 15. The dividend the previous four quarters was 16 1/2 cents a share.

5/3 seeks OK on debentures

Fifth Third Bancorp filed Thursday with the Securities and Exchange Commission to sell as much as $200 million in unsecured debt securities.

The Cincinnati banking company will sell junior subordinated debentures through trusts and use proceeds from the sales for general corporate purposes, the filing said. Details of the securities sale will be in a supplemental prospectus for the shelf offering, according to the registration statement. A shelf offering allows larger companies to register securities and sell them as financing needs arise.

LCA-Vision confirms center

LCA-Vision Inc., as expected, Thursday said it will create its 15th laser eye surgery center in the nation. The center in the Warren/Youngstown, Ohio, area will open March 10.

Cincinnati-based LCA has been rapidly expanding its network of surgery centers, undaunted by a $4 million loss last year due largely to heavy start-up costs. Dr. Stephen Joffe, LCA's chief executive officer, said the rate of new-center openings will slow for the balance of the year.

M.B.W. Foods picks S/Y&R

Sive/Young & Rubicam has been picked as media agency-of-record for Columbus-based M.B.W. Foods, maker of Mrs. Butterworth's syrup.

The size of the account was not disclosed.

Sive/Y&R will provide strategic planning and develop the creative, media planning and public relations campaigns for Mrs. Butterworth's regular and light syrups and pancake mix. The agency's Small Talk division will coordinate marketing efforts for the syrup that are targeted to children.

LTV Steel over EPA limits

LTV Steel Co. might need to spend $1 million or more on air-pollution equipment to reduce clean-air law violations at its Cleveland plant, the federal government says.

The Environmental Protection Agency said LTV exceeded limits for airborne particles - such as dust, smoke and ash - from two blast furnaces that make molten iron and one basic oxygen furnace that turns iron into steel. Two plant sources exceeded legal sulfur dioxide limits.

The alleged violations occurred during the past four years, the EPA said.