Ten chlorinated or fluorinated alkanes and alkenes were hydrolyzed in deionized aqueous solution, in "sea water", or in the presence of 11 different crushed solid minerals including sulfides, oxides, hydroxides, and aquifer materials. No changes in the observed hydrolysis rates were found upon changing from a pure water environment to one of high ionic strength or of significant potential heterogeneous catalytic activity for these typical halogenated hydrocarbons. Successive partial substitution of fluorine for chlorine in the ethanes was shown to retard hydrolysis by one to five orders of magnitude.