Table 4.

Test methods for sulfur compounds

ParameterTRL Report 447 (2001 & 2005) and BS 1377-3:2018BS 1377-3:1990BS EN 1744-1:2012Comments
Water-soluble sulfate (WS) (in 2:1 water/solids extract)TRL 447: Test 1
BS 1377: Clauses 7.3–7.7
Results in mg l-1 SO4
Clause 5.3 & 5.5
Results in g l-1 SO3
Clause 10.1
Results in % SO3 of dry sample mass
Provided units are converted to mg l-1 SO4, there should be no substantial difference between the methods for rocks and aggregates. There may be differences for weak rock because of differences in sample preparation.
BS EN 1744-1 Clause 10.1 is not suitable for testing of soils as preparation of the whole sample may give lower results and the higher drying temperature of 110 ± 5 °C will affect sulfate solubility in the 2:1 water/soil extract.
The preparation of the solution for analysis using hot water is unsuitable for natural aggregates, soils and rocks.
pHTRL447 Test 1
BS 1377 Clause 12.5
Clause 9No testIf BS EN 1744-1 is used, pH should be determined as part of the Clause 10.1 test.
Acid-soluble sulfate (AS)TRL447: Test 2
BS 1377 Clause 7.9
Results in % SO4
Clause 5.2 & 5.5
Result in % SO3
Clause 12
Result in % SO3
Provided units are correctly converted, there should be no difference between the methods for fine-grained soils. There may be differences for coarse-grained soils and weak rock because of differences in sample preparation.
Total sulfur (TS)TRL447 Test 4A & 4B
BS 1377 Clause 7.10
Results in % S
No testClause 11.2
Result in % S
The high temperature combustion methods used in TRL 447 Test No. 4B, BS 1377 Clause and BS EN 1744-1 Clause 11.2 are closely similar and these are the preferred methods.
The BS EN 1744-1 Clause 11.1 test should not be used as dissolution with H2O2/HCl employed in the latter is not suitable for complex mixtures of sulfur and silicate minerals.
Total reduced sulfur (TRS)TRL447 Test 3
BS1377 Clause 7.11
Results in % S
No testNo testThe TRL 447/BS1377 Test is the only one that will extract all forms of reduced sulfur, including the most common form, pyrite, as well as monosulfides.
TRS may generally be determined by difference using [TRS = TS‒AS/3]; however, TRS will be over-estimated if sulfates resistant to acid are present, e.g. barite (BaSO4).
Monosulfide sulfur (MS)/Acid-soluble sulfidesTRL447 Test 5
BS1377 Clause 7.12
Results in %S
No testClause 13
Results in %S
Results should be similar for both methods. However, both tests extract only monosulfide minerals. These are usually highly reactive but form only a small part of the total reduced sulfur content.

Reid et al. (2017).