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Standard method

Method (adapted from APHA Standard Method 4500-SO42- E. Turbidimetric Method)

Sulfate ion (SO42-) is precipitated in an acetic acid medium with barium chloride (BaCl2) so as to form barium sulfate (BaSO4) crystals of uniform size. Light absorbance of the BaSO4 suspension is measured at 420 nm.

Reagents from Labchem


 Catalog #


 Shelf life

Buffer Solution A * LC125702 $85.20 for 1 L 36 months
Barium chloride, ACS LC115609 $28.60 for  24 months
Sulfate standard, 100 ppm LC255001 $28 for 500 mL 12 months


  • Transfer 8 mL of sample to a fresh screw-capped tube
  • Add 2 mL of Buffer Solution A and mix
  • Add 0.025 g of barium chloride and mix
  • Measure turbidity with the green LED
* Note: for samples with SO42- < 10 ppm, use Buffer Solution B (Cat # LC125702)