Equipment: Spectrophotometer “Evolution-201”

Goal

 

Determination of phosphate ions in soils

Area

Geochemical mapping, archeology, paleogeography

The maps of phosphates distribution allows to identify:

-  anthropogenic load in study area ;

-  to identify the possible functional areas of the archaeological site;

-  to determine the edge line of the ancient water reservoirs

Sampling

Sampling of soil is performed according to a predetermined plan depending upon the purpose of the study. Mass selected samples should be not less than 20 g from each point.

Samples  preparation

The obtained  samples are dried in a oven  at a temperature of 50 – 60 oC to remove free water

The method of  phosphate determination

 

Method for determining phosphates is described in [Bulatov, Kalinkin, 1986]. The method is based on the reduction reaction of the complex to the molybden-phosphoric compounds presumably meets the formula (MoO2*4MoO3)2*H3PO4 with blue color and photometry of solutions at l=590 nm. For photometry spectrophotometer Evolution 201 is used.

Accuracy

The accuracy is 0.1 % content of P2O5 in the sample

Reagents required

Hydrochloric acid

 Sulfuric acid

Ammonium molybdate

Sodium acetate

Phosphate potassium monosubstituted

Sodium sulfite

Sodium bisulfite

Distilled water

The necessary equipment

Spectrophotometer Evolution 201

Hood

One-hotplate electric cooker

Literature

M. I. Bulatov, I. P. Kalinkin. A practical guide to photometric methods of analysis. Leningrad, "Chemistry",1986, 432. (in Russian)