William McAllister Jr., a chemist whose career as a quality-control expert for the Southern States farm cooperative in South Baltimore spanned 40 years, died Monday at Baltimore County General Hospital after complications from an aortic aneurysm.

Graveside services for Mr. McAllister, who was 75, will be held at 11 a.m. tomorrow at Lakeview Memorial Park, 2724 Liberty Road, Sykesville.

In 1941, he married the former Lucille Barnett, another native of Morgantown, W.Va. The couple celebrated their 50th wedding anniversary in December. Catonsville residents for more than three decades, they moved to the Westminster area after his retirement.

Mr. McAllister was active in the American Society of Quality Control Engineers. He was an avid gardener and an accomplished woodworker.

Besides his wife, he is survived by two sons, William McAllister III of Sykesville and Robert F. McAllister of Monkton; a daughter, Patricia L. McAllister of Westminster; and a grandson, William McAllister IV of Sykesville.