A Montgomery County Circuit Court jury decided yesterday that a major chemical manufacturer and its local distributor were not responsible for the death four years ago of a Silver Spring man from the effects of prolonged exposure to the powerful solvent benzene.

Joan McDonald, the widow of Robert Ray McDonald, 43, had charged that Sun Oil of Pennsylvania and Textile Chemical Co. Inc., of Baltimore, had failed to place adequate warning labels on the 55-gallon drums of benzene used at the Washington Millinery Co. in Rockville, where her husband was employed.

Expert witnesses called on behalf of Mrs. McDonald during the seven-day trial before Judge Rosalyn B. Bell testified that prolonged contact with the chemical, used to dissolve dyes used to color handbags, veils and other garments, caused McDonald to contract myelofibrosis. They said the illness, which results when the bone marrow is no longer able to produce healthy red blood cells, led to his death on July 6, 1978.

But Francis Ford, Sun Oil's attorney, and Kevin J. McCarthy, the lawyer representing Textile Chemical, argued that their clients had placed a label on the product indicating that it was a "dangerous product."

McCarthy told the jury in his closing statement that McDonald contributed to his own illness because he ignored federal safety guidelines for the use of benzene.

McDonald's attorney, Darrell L. Longest, had asked the jury to return a verdict that would include $457,000 in compensatory damages.