I am working on sulphur element in my PhD thesis. I need a protocol of HEAT SOLUBLE SULPHUR (1% NaCl) method used in soil analysis.
The method used in Australia is names 'KCl 40' , i.e. a KCl solution at 40 degrees C. I do not currently have access to the concentration as I'm not in my office and I did not see it on Google. The test assumes that you have access to ICP as some of the extracted S is organic. Otherwise an oxidation step would be required before measurement as sulfate
sir,
actually this is quite different from "KCl 40" and tedious and of course some extracted sulphur is organic.
Mr.Ashish Rai,the original method of heat-soluble sulphur was described by Williams and Steinbergs ( 1959). Inorganic sulphate-S and a portion of organically bound-S are mobilized by heat treatments and extraction with 1.0 per cent sodium chloride solution.Sulphate -S is converted into barium sulphate suspension using barium chloride crystals and a special conditioning reagent.The resulting turbidity is measured by a spectro-photometer(Cottenie et al.1979).You can find the detailed procedure described in a methods manual given below.
Analysis of soils for pH, EC and Available Major Nutrients by Subba Rao, A. and Sammi Reddy , K.(2005) In: Methods of Analysis of Soils,Plants,Waters,Fertilisers &Organic manures.HLS Tandon(Editor) Fertilser Development and Consultation organization, 204-204A Bhanot Corner,1-2 Pamposh Enclave, New Delhi-110048(India)E-mail:[email protected] or [email protected]
5 g soil is extracted with 33 ml of 1% sodium chloride solution. Twenty five ml aliquot is evaporated to dryness with 2 ml of 3% H2O2. It is kept in oven at 102 o C for 1 h to remove excess peroxide. After cooling 25 ml distilled water is added to residue and filtered to remove suspended matter. Sulphur in the extract is estimated turbidometrically.
William and Steinberg 1959. Aust J Ag. Res. 10:340-352
Chesnin and Yien 1951. Soil Sci Soc. Am. Proc.15:149-151
Rao Sir and Gaind Madam,
Thank u very much for clearance.
Can u explain what actually NaCl does in all the process?
Mr.Ashish, 1% NaCl is an extractant for the extraction of sulphate and a portion of organic sulphur. Most probably it has neutral or slightly alkaline pH (you can check before extraction) and provides better extraction conditions than distilled water whose pH may not remain stable at 7.0 because of the absorption of CO2(pH may go down).An alternative method to heat- soluble method is extraction with sodium bicarbonate(0.5M MNaHCO3) at 1:4 soil solution ratio and 60 minute equilibration(Kilmer and Nearpass 1960).This extrctant extracts water-soluble,adsorbed and labile organic sulphate-S.
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