Solubility of lead sulfate in solutions of sulfuric acid, determined by dithizone with a photronic cell

Abstract

New determinations of the solubility of lead sulfate in sulfuric acid solutions have been made, using diphenylthiocarbazone, commonly called dithizone, as the r eagent. This provides a very sensitive method for small quantities of lead. The eq uivalence point was detected by a simple arrangement of a photronic cell and color filter. The range of concentrations of acid extended from 0.1 to 50 percent H 2S04• Determinations of the lead could be made with an average error not exceeding 0.7 microgram (,..g). Determinations were made at 25° and 0° C, employing solutions, some of which were brought to saturation equilibriu m from undersaturation and others from supersaturation. Important maxima and minima in the solubility curves which had not been reported previously were found. Tables are given for the solubility of the salt at 25° and 0° C. Comp ari-son is made of the effect of H 2S0 4 on the solubility of lead and mercurous sul-fates. The trend of the curves for these is strikingly similar, although the latter is more than 80 times as soluble.