The Justice Department has relayed to the U.S. attorney in Chicago a request by Sen. Howard M. Metzenbaum (D-Ohio) to reopen an investigation into Syntex Corp.'s elimination of salt from infant formulas in 1978, Metzenbaum said this week.

Metzenbaum made the request to Assistant Attorney General Richard K. Willard on Dec. 20, citing a memo in which the company's chief medical officer termed one justification for the action "a seeming falsehood."

Willard replied on Jan. 3 that because a now-closed investigation had been made jointly by the Office of Consumer Litigation in the Justice Department's Civil Division and a grand jury in Chicago, he was referring the request to the Chicago prosecutor, Anton R. Valukas, "to evaluate the merits of the matter and to take any appropriate action."

The deletion of salt drastically reduced the levels of chloride -- an essential nutrient -- in Neo-Mull-Soy and Cho-Free, the brands of infant formula that Syntex recalled in 1979 and stopped selling in 1981.

As a substitute for breast milk, formula is supposed to contain all of the nutrients needed by infants during their period of swiftest brain growth. In product-liability lawsuits, parents have claimed, and Syntex has denied, that the defective products inflicted lasting, and even fatal, harm on numerous children.

The Food and Drug Administration sent the case to the Justice Department in June 1981 for possible prosecution of Syntex, a Palo Alto, Calif., pharmaceutical conglomerate, and at least one of its officials, for violating provisions of the food and drug laws covering the adulteration and misbranding of products.

In September 1983, after the Justice Department tentatively turned down the FDA request, agency chief counsel Thomas Scarlett protested to the department that the chloride deficiency occurred because Syntex "chose not to incur the expense, in time and effort, of instituting an adequate quality-control system."

Meanwhile, Valukas' predecessor as U.S. attorney presented the matter to a grand jury. No charges were filed, either by the grand jury or by the Justice Department's Civil Division. The latter made the final decision not to prosecute in May 1984.