Sulphate Test Kit

CHEMetrics offers test kits for the determination of Sulphate in aqueous solutions employing the well-known Turbidimetric method to deliver sensitivity and accuracy within two minutes or less. Based on CHEMetrics patented Self-Filling Reagent Ampoule technology. Each ampoule contains pre-measured reagents for a single test. Premixed. Premeasured. Precise. Each kit contains 30 tests. The Vacu-vials® instrumental kit relies on CHEMetrics V-2000 or V-3000 multi-analyte photometers which contain a pre-programmed sulphate calibration to provide direct read test result. Alternatively, spectrophotometers capable of accepting a 13-mm diameter round cell can be used.

Turbidimetric Method

The Sulphate Vacu-vials® test kit employs the turbidimetric method. Sulphate ion reacts with barium chloride in an acidic solution to form a suspension of barium sulphate crystals of uniform size. The resulting turbidity is proportional to the sulphate concentration of the sample. Results are expressed as ppm (mg/l) SO₄.

References:
APHA Standard Methods, 15^th ed., Method 426 C (1980).
USEPA Methods for Chemical Analysis of Water and Wastes, Method 375.4 (1983).
ASTM D 516-07, Sulphate Ion in Water.

Technical Data Sheet

Applications

Industrial sulphates are made from plant or petroleum sources and are used in a wide variety of industries, including: gypsum in manufacture of plaster in construction industry; copper sulphate as an algicide and galvanic cell electrolite; iron sulphate as an iron supplement; magnesium sulphate as Epsom salts; sodium laureth sulphate (SLES) as a detergent or foaming agent in soaps, shampoos, toothpastes and cosmetics; and polyhalite as a fertiser.

Sulphate levels must be monitored in cooling water and ion exchange water softening systems in order to prevent calcium sulphate scale formation.

Environmental testing of sulphate can help identify run-off pollution or industrial contamination of natural waters. Geotechnical engineers perform sulphate analysis in water when studying factors influencing soil corrosion and sulphate attack on concrete structures.

While sulphate is common at low concentrations in natural waters, at high concentrations it can cause a foul odour or taste. For this reason, drinking water testing for sulphate has become standardised. Neither the EU Drinking Water Directive nor DEFRA water quality regulations specify standards for hardness. The USEPA has established a Secondary Drinking Water Standard of 250 mg/l (ppm) for sulphate in potable water. The Specified Concentration or Value (SCV) for drinking water for UK at the supply point is the same, as is the Specified Concentration or Value (SCV) for Ireland. Sulphate levels are also measured in the beverage industry due to its effect on odour and taste.

What is Sulphate?

Sulphate is a polyatomic anion with the chemical formula SO4^2-. Sulphate is a tetrahedral molecule with sulphur at the centre. Sulphur and oxygen atoms have oxidation state of +6 and -2 respectively. Sulphates are salts of sulphuric acid (H₂SO₄) when the acid donates both of its protons. When sulphuric acid donates one hydrogen ion, the resulting conjugate base is hydrogen sulphate ( bisulphate), HSO₄^-. When HSO₄^- donates a further proton, the resulting conjugate base is SO42-. Other sulphur oxyanions exist with differing proportions of sulphur and oxygen, including sulphite (SO₃^2-), thiosulphate (S₂O₃^2-) and so on.

Sulphate occurs naturally and can be found in widely varying concentrations in surface and groundwater owing to contact with various mineral deposits and strata. Chemical derivatives of sulphate are usually water-soluble. Water hardness is caused almost entirely by the chlorides and sulphates of calcium and magnesium. Microscopic sulphate particles are generated by combustion of fossil fuels and biomass, increasing atmospheric acidity and other unwanted environmental effectcs.