The invention relates to a process to make stabilized PVC wherein use is made of at least one compound of the formula ##STR1##

wherein M is selected from the group consisting of alkali metals, alkali earth metals, Al, and transition elements, and R is selected from the group consisting of substituted, linear or branched, alkyl, cycloalkyl, aryl, alkaryl, and aralkyl moieties, the substituents comprising at least one or more electron-withdrawing groups, as a color stability booster.