Marion Matlack, 82, a retired chemist who had been with the Department of Agriculture for 33 years, died Sunday at Arlington Hospital after a heart attack.

Mr. Matlack was born in Sorrento, Fla. and graduated from the University of Florida. He served in the Army for several months at the end of World War I.

In 1921 he moved to Washington and became an assistant chemist at the National Bureau of Standards. He received a masters degree from George Washinton University in 1923.

The following year, Mr. Matlack moved to Atlanta, where he was an instructor at the Georgia Institute of Technology. He was later a fellow at the University of Florida from 1925 to 1927. Mr. Matlack then did graduate work at the University of Wisconsin in Madison, and was awarded a doctorate in 1928. He spent the next two years in Battle Creek, Mich., as a research chemist with the General Foods Corporation.

He returned to Washington in 1930, and joined the Department of Agriculture's bureau of chemistry and soils. During World War II, he worked as a nutritionist for the War Food Administration. Mr. Matlack was with marketing service at Agriculture from 1953 to 1956, and was a biochemist with the research service unitl his retirement in 1963.

He was a member of several horticultural groups, including the American Rhododendron Society, the National Capital Day Lily Club and the American Hemerocallis Society.

He also was active in the National Genealogical Society, the American Association for the Advancement of Science and the American Chemical Society. He lived in Arlington.

His wife the former June Royal died in 1969.

Survivors include four sons, Albert F., of Wilmington, Del., James M., of Arlington, Donald E., of Laurel and Philip R., of Fairfax, and seven grandchildren.