Six sodium dialkyl dithiophosphates salts, ethyl through butyl, are determined polarographically. Curves of current versus concentration are linear up to 10-3M. The anodic half-w-ave potentials become increasingly negative with respect to the saturated calomel electrode as the size of the alkyl group increases. Information concerning the electrode reaction was obtained from the relation between the limiting current and the half-wave potentials at various concentrations of the same salt and by separate experiments, wherein products could be recovered, using a mercury macro electrode at the same half-wave potentials found in the polarographic work. The probable electrode reactions are the oxidation of the mercury to the mercurous ion and a reaction of this ion with the dialkyl dithiophosphate ion to produce free mercury and the mercuric salt. A polarographic determination of a dialkyl dithiophosphate was made at a micro platinum anode and again at a platinum macroelectrode, using the same half-wave potential.Bis-(dialkyldithiophosphoryl) disulfides are formed at this anode. METHOD for the polarographic determination of dialkyl