This Standard specifies a method for the determination of residual acid soluble sulfur (S_RAS) in acid sulfate soil after peroxide digestion (AS 4969.3) and the determination of peroxide sulfur (S_P) (AS 4969.5).

In order to perform this method, AS 4969.3 and AS 4969.5 shall have already been performed on the same test portion.

NOTES:

1 This extraction procedure recovers the relatively insoluble iron and aluminium hydroxy sulfate compounds (e.g. jarosite, natrojarosite, basaluminite) which are not measured to any significant extent in S_P.

2S_RAS, unlike S_NAS, (AS 4969.11) does not measure significant sulfur from organic matter as this is removed during rinsing of the soil residue. Some laboratories may prefer to perform S_NAS analysis for operational reasons.

3 This procedure would normally only be performed on a soil with a potassium chloride pH 4.5 (pH_KCl, (AS 4969.2) or where jarosite/natrojarosite and similar minerals have been identified in the soil when it was sampled.