One of the most famous Catalan and Spanish scientists. He devoted his life to research in organic chemistry. His main contribution to science was the development of perchloro-organic chemistry, which he began in 1954 with the discovery of a potent chlorination agent. In 1964 he discovered the Inert Free Radicals, a class of trivalent carbon species of exceptional stability, which opened the door to a new era in organic chemistry.

Born in Mont-Roig del Camp in 1920, he moved to Barcelona in the 1930s when his father, a state school teacher, was posted to the capital. A man committed to freedom, Ballester volunteered at the age of 17 to defend the Spanish Republic against fascist aggression. He suffered the shameful refugee camps in the south of France until he was able to return to Barcelona. At the end of the Spanish civil war, he obtained a doctorate in Chemistry and Biological Sciences with an excellent cum laude mark for his doctoral thesis.

He graduated in Chemistry from the University of Barcelona, and also obtained degrees in Physics and Mathematics from the University of Montpellier. He was a chemical engineer at the Institute of Chemistry of the University of Montpellier (1941) and obtained a PhD in Physical Sciences from the Sorbonne (Paris, 1948).