Analytical Methods:PSD Pretreatment

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Particle size analysis – sample pre-treatment
Clay particles and organic matter can cause soil materials to clump together. To prevent this pretreatment is needed. Hydrogen peroxide is used to remove organic matter in soils with greater than 5% organic matter content. Calgon is routinely to all samples used for particle size analysis to prevent clay particles sticking (flocculating) together.

Safety
1 Always consult chemical safety data sheets and follow appropriate health and safety protocols before handling or using chemicals.

Many chemical saftey data sheets are available here from this Oxford University based database.

Hydrogen peroxide pretreatment

 * 27-30% H2O2


 * 1) Transfer the sample to a tall glass beaker and add 10 ml of 30% H2O2 (WARNING!! H2O2 is a strong oxidizer and will readily react with hair, skin, eyeballs, clothes, etc.). If the reaction is vigorous add further 10ml portions of H2O2 until no reaction occurs. Record how much is added.
 * 2) If the sample reaction threatens to boil over a drop of amyl alcohol may be used to dampen the frothing.
 * 3) When the reaction diminishes, add approximately 50 ml of distilled water and heat on a hot plate at 90oC for 1 hour. Watch carefully to prevent boil over.
 * 4) Remove from heat source and let cool.

Calgon pretreatment

 * Calgon: Dissolve 75 grams of sodium hexametaphosphate in 2 litres of distilled water
 * 1) Place the treated solution into plastic bottles and add 10 ml of sodium hexametaphosphate (Calgon), put caps on bottles, check for leaks, and put on the shaker. Leave samples on shaker overnight (or at least 6 hours).
 * 2) Pipette 10ml Calgon into a weighed evaporating dish and dry at 105oC, reweigh and subtract the original wight of the dish to obtain the weight of the residue (R).

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