Following are profiles of Salomon Brothers, one of the world's biggest investment firms, and Phibro Corp., the largest publicly owned commodities trading firm, which purchased Salomon yesterday .

Although it has annual sales that put it ahead of all but the top 10 of the Fortune 500, Phibro Corp. is one of the corporate world's great unknowns, at least as far as the general public is concerned.

That's partly because Phibro Corp. is the world's newest corporate behemoth. It is the larger fragment from an April decision that split Engelhard Minerals & Chemicals Corp. into Engelhard Corp. and Phibro, following approval by the stockholders in May. But Phibro is not unknown to buyers and producers in commodities ranging from oil to cocoa. As a separate company, Phibro would have had revenues last year of $23.7 billion and profits of $466.8 million.

Phibro was founded as Philipp Brothers in 1914, and its specialty was trading in minerals, metals and ores. Starting early on, however, was an interest in oil and petrochemicals that has now grown to account for almost half of earnings. In 1980, oil accounted for 44 percent of sales, down from 48 percent the year before.Company officials hope to boost the proportion back up with a $307 million purchase last year of oil and gas rights in northern Canada's Beaufort Sea.

Phibro's role in minerals is as the world's leading marketer, leading some to dub it a "supertrader." Phibro purchases the great majority of its minerals from other producers. A spokesman for Salomon Brothers yesterday said that the investment banking house may prove a good partner for Phibro by helping to finance new projects by some of the supertrader's key suppliers.

Over the past five years, Phibro's sales have quadrupled. On a per share basis, annual increases in earnings have averaged 36.6 percent on average sales increases of 35.6 percent.

Philipp Brother's emphasis is heavily international. In 1980, roughly half of revenues came derived from outside the United States. The Salomon spokesman said that such international ties would help the investment house build up foreign business.

Phibro's links abroad have recently been a source of controversy, since Phibro markets gold and other minerals from South African operations. And Anglo American Corp., the mining combine controlled by South African magnate Harry Oppenheimer, holds a stake in Phibro estimated at about one-third.

Phibro merged with Engelhard Industries in 1967 in hopes that it could find common marketing and financial support with the minerals and chemicals processing concern. But by last April "the synergy that brought us together is gone," said David Tendler, Phibro president and former vice-chairman of Engelhard. Others questioned whether it ever existed. The two firms' operations and finances remained so distinct that arrangements for the split took little more than a mouth