HCl acid washing is usually applied to samples destined for combustion.
Because HCl reacts with carbonate to produce CO2, its use in pretreatment work is restricted to non-carbonate samples.
Many samples from terrestrial environments, such as wood, charcoal and peat, will often contain small amounts of absorbed carbonates from percolating groundwater.
This material is non-contemporaneous and must be removed.
Solvents are heated in a round-bottomed flask and evaporate up through a siphon into a condenser.
Upon condensing they drip down through the pyrex wool covering the sample and then through the sample itself, leaching the contaminants through the profile and dissolving them.
There are two major decay contaminants; humic acids and fulvic acids.
The aim is to reduce the p H levels of the sample to a neutral level by continual rinsing.
During this treatment, regular litmus readings are taken to determine the extent of the acidity remaining.
Sodium hydroxide (Na OH) treatment is usually associated with the removal of humic acid contamination from soils, wood, charcoal and peat samples.
Humic acids are the mobile decay products of biological materials deposited in the vicinity of the sample matrix.The humic fraction is acid insoluble and is removed using a base extraction method.