HAPAB A rapid, selective semimicro gravimetric method for the determination of mercury is presented. The method takes advantage of the principle of precipitation from homogenous solution ( PFHS ). Of various compounds tested. N-allylothio-urea ( ATU ) was found to be a good PHFS reagent for mercury. The sample of mercury as mercuric chloride was reacted with a six-fold excess of ATU over mercury. After heating to 60 C, ammonium hydroxide solution was added to obtain a pH of 9. The black precipitate ( mercury sulfide ) which was formed was washed, dried and weighed for mercury determination. Mercury, in quantities of 2 to 100 mg, was determined in 12 samples without impurities and in 11 samples in the presence of diverse ions, with a mean relative error of less than 1%. The reagent appears to be selective for mercury in the presence of masking agents, which do not prevent the precipitation of mercury sulfide. The following anions, tested in the form of their sodium, ammonium and potassium salts, do not interfere with the analysis; acetate, arsenate, arsenite, carbonate, chloride, citrate, ferrocyanate, nitrate, nitrite, sulfate, tartrate, thiocyanate and thiosulfate; cyanide, iodide and phosphte do interfere. Of those cations which form insoluble sulfides, only silver interfere. Analysis 69/10/00, 366 1969
