The precipitation effects obtained by mixing silver nitrate solutions with solutions of primary and secondary orthoarsenate salts in water and 30 and 50% ethanol-water mixtures have been investigated. The systems were preparedin statu nascendi and the changes in turbidity followed with time. The data are plotted as turbidity at a certain time after mixing against concentration of one precipitating component while the other precipitation component is kept constant. Such turbidity-concentration curves show a number of maxima and minima, the character of which is discussed in the paper.