William A. Mitchell, 92, the food scientist who invented Pop Rocks candy and discovered a substitute for tapioca, died July 26 at a care home in Stockton, Calif. He had congestive heart failure.

Mr. Mitchell, who worked as a chemist for General Foods Corp. in White Plains, N.Y., for 35 years until his retirement in 1976, held more than 70 patents, including inventions related to Cool Whip, quick-set Jell-O Gelatin and the drink mix Tang.

While working briefly for Eastman Kodak Company, he helped design a chemical process to develop the color green. He developed the tapioca substitute during World War II when tapioca supplies were running low.

Perhaps Mr. Mitchell's most famous invention was Pop Rocks -- the exploding candy that became a cultural phenomenon after it hit the market in 1975. He made the discovery accidentally, while trying to design an instant soft drink, when he put some sugar flavoring mixed with carbon dioxide in his mouth.

For years, Mr. Mitchell, who patented Pop Rocks in 1956, fought to dispel the myth that the carbonated candy was deadly if eaten while drinking carbonated drinks.

After his wife died in 1999, he moved to Stockton, where he developed food products for a daughter's Stockton research company.

Survivors include seven children.

William A. Mitchell's other patents related to Cool Whip, Jell-O and Tang. He worked for General Foods.