BY ROBERT H. BURRIS

KARL PAUL LINK was a carbohydrate chemist and plant biochemist, whose research changed direction abruptly when he initiated work on the isolation and characterization of the hemorrhagic factor produced in spoiled sweet clover hay. The isolation of a modified coumarin as the causative agent led Link and his colleagues to the synthesis of a variety of anticoagulants that have had wide medical application as anticlotting agents and that have also proved highly effective as rodenticides.

Karl Paul Gerhard Link was born in LaPorte, Indiana, the eighth of ten children, to Frederika (Mohr) and George Link, a Missouri Synod Lutheran minister. At age two he survived a serious case of pneumonia; he never was a robust child. Karl characterized his early family life as ''on the edge of poverty," but his parents, brothers, and sisters were supportive. His father had a fine library that the children were encouraged to use, and they possessed a piano that had been brought from Germany by Karl's maternal grandparents. As Karl's sister Margret stated of their group singing, "we cut our eye teeth on the Bach chorals. So a deep appreciation of literature, poetry, and music became a part of us. We spoke both German and English."

When Karl was two years old, his father developed a throat