This International Standard is applicable to as-received (feld-moist) samples and specifies two different procedures for the liberation of cyanide from the soil:
- direct liberation of hydrogen cyanide using orthophosphoric acid (normative);
- extraction with sodium hydroxide solution and subsequent liberation using orthophosphoric acid (informative, see Annex B).

The liberated cyanide is determined either by a photometric method or a titrimetric method using an indicator.

The method is applicable to all types of soil.

Under the conditions specified in this International Standard, the lower limit of application is 0,5 mg/kg of total cyanide (expressed on the as-received basis) for photometric determination and 10 mg/kg for titrimetric determination.

NOTE Using the alkaline extraction followed by liberation using phosphoric acid, the lower limit of application is 1 mg/kg of total cyanide (expressed on the as-received basis) for photometric determination and 30 mg/kg for titrimetric determination.