Hot acidity is a variation of the standard Acidity titration using NaOH, with some pretreatment steps performed before the titration. It is outlined in Standard Methods SM2310B, officially called “hot peroxide treatment procedure for acidity determination”. This method is applicable to mine wastes and other samples containing large amounts of metals such as heavy industrial WW.
From SM2310B:
- Use the hot peroxide procedure to pretreat samples known or suspected to contain hydrolysable metal ions or reduced forms of polyvalent cation, such as iron pickle liquors, acid mine drainage, and other industrial wastes.
- Hot peroxide treatment acidity method:
- Pipet sample volume into vessel
- Measure pH
- If pH > 4.0, add small increments of 0.02N H2SO4 to reduce pH to 4.0 or less
- Remove samples from MANTECH system
- Add 5 drops of 30% H2O2 and boil for 2 to 5 minutes
- Cool to room temperature
- Place samples back on MANTECH system and titrate with standard alkali (NaOH) to pH 8.3
- The calculation for hot acidity is shown below:
- Acidity = [((mL NaOH consumed)*(Normality of NaOH)) – ((mL H2SO4 consumed)*(Normality of H2SO4))*50,000]/Sample volume
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