Equipment: Spectrophotometer "Evolution-201"


Determination of phosphate ions in soils.


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 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 50-60oC 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.


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


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