Silver electrodeposits prepared from AgNO3 solutions never give compact, smooth plates unless an organic additive, such as tartaric acid (H(2)A), is used as growth inhibitor. It was shown previously that the relevant chemical entity controlling growth inhibition is the bulk concentration of a neutral associate Ag(HA) formed in the solution between Ag+ and tartaric monoanions HA(-). In the present work we extend this investigation to mixed water + dioxane solvent systems where the addition of dioxane, affecting the formation constant of Ag(HA), changes the bulk concentration of this associate. It was found that the associate Ag(HA) also formed in water + dioxane solvent systems is the active component in the solution governing the growth inhibition. On the concentration of this associate most of the structural features of Ag deposits (e.g., the grain size, the superficial roughness and the degree of the preferred orientation <1 1 0 >) depend.