NEW YORK, SEPT. 17 -- The stock market posted a small loss in quiet trading today, adding a bit more to the steep declines of the two previous sessions.

Analysts said traders were proceeding cautiously awaiting Friday's quarterly "triple witching hour."

The Dow Jones average of 30 industrials slipped 2.29 to 2527.90, bringing its loss since Monday's close to 85.14 points.

Bond prices, however, jumped by as much as a point or more, buoyed by reports that congressional negotiators were nearing a compromise on a deficit-cutting law.

The Treasury's closely watched 30-year bond rose 1 1/8 points, or about $11.25 for every $1,000 in face value. Its yield, which moves inversely to its price, dropped to 9.57 from 9.67 percent late Wednesday. Corporate and municipal bonds also moved higher.

"The mood is a little more buoyant than it has been for a long time," said John Sebastian, an executive vice president at Clayton Brown & Associates of Chicago. He noted that a successful compromise would be enough to lift the credit markets out of the doldrums, where they have languished all summer.

The dollar continued little changed in quiet trading. Against the West German mark, the dollar ended at 1.8155, up from Wednesday's 1.8135. The dollar slipped to 143.40 yen, from 143.75. Overnight in Tokyo, the dollar ended fractionally higher at 143.82, up 0.02 yen from 143.80 Wednesday.

Volume on the New York Stock Exchange came to 150.71 million shares, down from 195.74 million in the previous session.

Analysts said spotty declines in interest rates helped lend the market some support.

But they also said traders were leery of committing themselves in advance of the triple witching hour Friday involving a group of expiring stock index futures, stock index options and options on individual stocks.

Program trading maneuvers by professionals using these contracts and the stocks that make up the indexes has been cited as a primary force behind the market's drop this week.

That situation has left Wall Streeters guessing about whether further storms are in store for the market at the witching hour, which has often in the past produced wide swings in stock prices.

An experimental system adopted at the last witching hour, in June, with the aim of smoothing out the process, will be used again Friday, putting settlement of some contracts at the opening rather than the close of trading.

Brockway Inc. jumped 19 1/8 to 58 3/8, pacing the percentage gain leaders among Big Board issues on word that Owens-Illinois was negotiating a deal to acquire the company for $60 a share.

Teledyne, which has a large chunk of Brockway stock, climbed 11 3/4 to 369 1/2.

Citicorp led the active list, down 3/4 at 57 1/2 on turnover of more than 5 million shares. The company sold 20 million new shares at 58 1/4.

Federal Express gained 3 3/4 to 69 1/4. The company reported a slight decline in earnings from continuing operations for its latest fiscal quarter, but the results were better than some analysts' advance estimates.

Nynex rose 1 3/8 to 75. The company reported plans to buy back as much as 5 percent of its outstanding stock.

Home Shopping Network, traded on the American Stock Exchange, fell 7/8 to 14 1/8. Home Shopping said it plans to reorganize itself as a holding company.