Isopropylbenzene derivatives having the general formula: ##STR1## in which: R.sup.1 to R.sup.4 independently represent a hydrogen atom or a lower alkyl group having up to 4 carbon atoms, X.sup..crclbar. represents COO.sup..crclbar. or SO.sub.3.sup..crclbar., and R.sub.f represents a fluorinated organic radical. The compounds may be applied to surfaces liable to be or become negatively charged to suppress spark discharges from such surfaces. Those compounds in which at least two of R.sup.2, R.sup.3 and R.sup.4 are alkyl, are particularly useful in the top coat of photographic films to eliminate marks caused by spark discharges.