The three methods specified are applicable to water containing less than 50 mg per litre and less than 100 mg of total cyanide per litre, but higher concentrations may be determined by suitable dilution of the sample. The methods suitable and corresponding ranges are as follows: photometric method with pyridine/barbituric acid: 0,002 to 0,025 mg; titrimetric method using the tyndall effect: > 0,005 mg; titrimetric method using an indicator: > 0,05 mg. Ions and compounds interfering with the determination are listed in table 1.