The paper includes the results in respect of the formation of basic and neutral Zinc-O,O＇-bis-2-ethylhexyldithiophosphate (ZnDTP) from O,O＇-bis-2-ethylhexylphosphorodithioic acid and zinc oxide during a semibatch operation. On the one hand was the zinc oxide batchwise dosed to a solution of the dithioic acid in mineral oil and on the other hand the acid continuous to a zinc oxide/oil-suspension dosed. The reaction course to the neutral and basic compounds is in dependence of the reaction guide and on the excess of zinc oxide fundamental different. During the batchwise addition of zinc oxide quick equilibrium＇s of substitution of ligands dominate to the formation of the stoichiometric compound and the basic compound is formed in a consecutive reaction also with high excess of zinc oxide only in small quantities. During the continuous dosage of dithioic acid at first basic salt is formed, which is decomposed to neutral salt in the course of further conversion. In this way any high contents of basic salt are realisable in dependence on the excess of zinc oxide in the mixture of reaction product. The synthesis of ZnDTP by continuous addition of dithioic acid is a reaction controlled by dosage. The industrial realisation was modelled in a jacket cooled 6,3 m(3) vessel by the help of the results of calorimetric investigations.