Mercury below one part per million in soil and grain samples is difficult or tedious to determine by available methodsle2. Materials low in mercury require large samples resulting in solutions of large volumes and high acidity; both interfere with accurate analysis. The residual finely divided particles in soil digests adsorb mercury(I1) and must be centrifuged and filtered using a chloride wash solution3.
In recent years, several analytical methods for mercury using the tin(II) reduction technique have appeared. BARTLETT AND MCNABB~ successfully applied the reduction technique to a volumetric analysis of macro and semimicro cluartities of mercury in organic and inorganic compounds.
MILLER ANI) WACHTER~ used the reduction technique combined with a steam distillation procedure to determine pug and submicrogram quantities of mercury in alloys. They demonstrated that up to 15 ,ug of mercury could easily be distilled from a dilute sulfuric acid medium. The MILLER AND WACHTER technique has been applied to biological materialsO*'. Small quantities of mercury have been determined in dilute solutions of organic mercury compounds by ti strong phosphoric acid-tin(II) reduction method in which mercury is carried from an electrically heated flask by a slow stream of carbon diosidea. Very dilute solutions must first be concentrated by coprecipitation with ferric or cadmium sulfide. The proposed method usesa concentrating aeration procedure at room temp. following digestion of the samples with sulfuric acid, hydrogen peroxide and potassium permanganate.
Its chief advantages are elimination of filtration, applicability to mercury solutions in sulfuric acid to 22 N, nitric acid to 8 N, and nitric and sulfuric mixtures to 4 N and 8 iV respectively, and ability to concentrate dilute mercury solutions during the process of mercury separation in order that the entire sample may be taken for analysis. Final analyses are made from solutions of constant composition and volume regardless of the original material and volume of the digest or solution.
Reagents EXPERIMENTAL ,Water. Use water redistilled from an all-Pyrex distillation unit. Hydrogen $evoxide. 50% (Buffalo Electrochemical Co.).
Hydroxylamwoniacm
sulfate. 257& dithizone-extracted. Sodilcnt chloride. ACS grade, 5 N, dithizone-estracted.