The standard molar enthalpies of formation of crystalline dialkyldithiocarbamate chelates of mercury(II) were determined by using reaction-solution calorirnetry. Two different complexes were studied: Hg(S(2)CNR(2))(2) with R = CH(3) (Me) and i-C(3)H(7) (Pr(i)). The enthalpies of formation for the mercury complexes were determined in 1,2,-dichloroethane at 298 K. The hemolytic and heterolytic mean enthalpies of dissociation of the Hg-S bonds were calculated by using the standard molar enthalpy of the gaseous chelates.