Sulfate in Building Materials

Prove InstrumentsPhotometric or turbidimetric determination subsequent to water extraction/fusion melting

Differential analysis of sulfate soluble in hot water and total sulfate can be carried out with suitable sample preparation.

Sample Preparation - Hot Water Extraction

Prepare a fine powder of the sample and dry at 105 °C. Mix 5 g with 100 ml of water for analysis and boil for 30 minutes on a hot plate. Allow to cool, transfer the suspension to a 200-ml volumetric flask and make up to the mark with water for analysis. Mix well, filter through a paper filter and then use as sample for the determination of water-soluble sulfate.

Sample Preparation - Total Content

Mix 100 mg of the finely powdered material along and 10 pellets of sodium hydroxide, place in a nickel crucible and heat for 30 minutes at 550 °C in a muffle furnace. Allow to cool and carefully add 10 ml water for analysis. If necessary, heat gently to obtain a suspension. Adjust to approximately pH 5 with nitric acid. Using water for analysis, transfer the suspension to a 100-ml volumetric flask, make up to the mark with water for analysis and mix well. Filter through a paper filter before carrying out the analysis.

Analysis

Determine with the below mentioned test kits.

Calculation

Sulfate (water-soluble) content in % = analysis value in mg/l x 0.004
Sulfate (total) content in % = analysis value in mg/l x 0.1

Materials