“…The so-called 'inert carbon-free radicals' belong mainly to the perchlorodiphenylmethyl (Ballester & Riera, 1954), perchlorotriphenylmethyl (Ballester, 1967;Ballester, Riera, Castafier, Badfa & Mons6, 1971) and 9-phenylfluorenyl radical (Ballester, Castafier & Pujadas, 1971) classes. They have chemical and thermal stabilities which are higher than those of the majority of normal tetrahedral carbon compounds and materials.…”