Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:9:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 9 (pt 2/2)
Character Range: 793518–794975

sodium carbonate/sodium peroxide fusion (AOAC 1980).

9.3              Sulfate

    9.3.1         Scope and application
These methods are applicable to the determination of soluble and adsorbed inorganic sulfate in soils, sediments and other solids (AS 1289.4.2.1-1997, Rayment & Higginson 1992, ASTM C1580-09, Tabatabai 1982).

    9.3.2         Principle
The sample is shaken in a 1:5 soil:water extract, or in some cases a calcium phosphate solution (500 mg phosphorus/L) (Tabatabai 1982) and the resulting extractant subsequently analysed (APHA Method 4110). In the latter, phosphate ions displace adsorbed sulfate while calcium ions depress extraction of soil organic matter and thus eliminate interference from extractable organic sulfur.

9.4              Sulfide

    9.4.1         Scope and application
This method (US EPA SW-846, Method 9030B) is suitable for soil samples containing 0.2–50 mg/kg of sulfide. It measures 'total' sulfide, usually defined as acid-soluble sulfide. For soils with significant metal sulfides, total sulfide is defined as both the acid-soluble and acid-insoluble fractions, and both procedures should be employed.

    9.4.2         Principle
For acid-soluble sulfides, sulfide is separated out by adding sulfuric acid to a heated sample. For acid-insoluble sulfides (for example, metal sulfides such as CuS, SnS2) sulfide is separated by suspending the sample in concentrated hydrochloric acid with vigorous agitation.