Soil is natural subject composed of layers of different thickness of mineral composition. It includes the weathering of rocks minerals, plants, animals, microorganism decomposing organic matter, soil organisms, water and air. It is the survival foundation of most life on earth. Since ancient times, a large number of scientists have made the separation and study for larger particles contained in the soil, organic matter, humus acid and minerals. In various separation and purification ways, sodium metatungstate gravity separation method has some advantages such as simple process, no side effect and stable effect.

 

Sodium metatungstate is also called hexasodium tungstate hydrate. It is a kind of white crystal. Molecular weight is 2968.01. The density is 3.1 g/ml and the refractive index is 1.5555. Under atmospheric pressure, sodium metatungstate is stable. But avoid contacting with the material and the oxide. High density of sodium metatungstate, with non-toxic, easy preparation and recycled, are widely used in many fields.

 

Application in the field of soil science is mainly manifested in the following three aspects:

1. Separation of soil aggregation big particles: Jastrow adopted the sodium metatungstate gravity separation method to dry and separate samples and studied on he link between soil aggregate, micro particle natural body, and minerals organic matter. Yi Yang used sodium metatungstate as density separation medium and combined with the density separation method to study adsorption effect of soil carbon in river floodplains on polycyclic aromatic hydrocarbons.

2. Separation of soil C and N organic matter: Kramer studied the partial high content of C and N in sodium metatungstate impacting on the chemical properties of soil density separation. Roviro used different levels of density separation method to prepare three sodium metatungstate solutions and studied the calcium content in a certain amount of soil organic matter of Mediterranean forest area.

3. Separation of soil humus acid: Shindo used sodium metatungstate density separation method to isolate Japanese 24 charred debris in volcanic ash soil samples. It is concluded that they are important components of the ash black humus acid in soil. Sodium metatungstate has been used for separating fossil plants and minerals from the rich soil. Georgiadis used sodium metatungstate density fractionation to extract amorphous silica from soil.