Precipitation of lead chromate from homogeneous solution by pH increase with urea in the presence of organic acids

Abstract

An investigation has been carried out into the mechanism of formation of dense precipitates from homogeneous solution by pH increase with urea.

The addition of organic acids has been shown to exert a buffering action leading to the control of the otherwise rapid rise in pH, and allowing the formation of dense precipitates over pH ranges where this would not otherwise be possible. This has provided an explanation for the necessity, in many cases of precipitation from homogeneous solution, for the presence of suitable anions to produce dense precipitates.

These investigations have been applied to the determination of lead by precipitation from homogeneous solution as lead chromate. A satisfactory quantitative method has been evolved, which produces easily filterable stoicheiometric precipitates.