BS 6068-2.18:1986

This standard BS 6068-2.18:1986 Water quality. Physical, chemical and biochemical methods is classified in these ICS categories:

• 13.060.50 Examination of water for chemical substances

This Section of this British Standard specifies three methods for the determination of easily liberatable cyanide (see clause 2) in water.

The methods are applicable to water containing less than 50 mg of easily liberatable cyanide (as cyanide ions) per litre, and less than 100 mg of total cyanide (as cyanide ions) per litre, but higher concentrations may be determined by suitable dilution of the sample.

The methods and corresponding ranges of easily liberatable cyanide contents for which they are suitable are as follows:

• Photometric method with pyridine/barbituric acid: applicable when the absorption solution contains 0,002 to 0,025 mg of cyanide, corresponding to 0,02 to 0,25 mg/l in a 100 ml aliquot portion of the undiluted sample;
• Titrimetric method using the Tyndall effect: applicable when the absorption solution contains > 0,005 mg of cyanide, corresponding to > 0,05 mg/l in a 100 ml aliquot portion of the undiluted sample;
• Titrimetric method using an indicator: applicable when the absorption solution contains > 0,05 mg of cyanide, corresponding to >0,5 mg/l in a 100 ml aliquote portion of the undiluted sample.

A large number of ions and compounds interfere with the determination. These are listed in Table 1, together with the concentrations below which they do not interfere. If present singly or in combination, up to limiting concentrations, they do not interfere with the separation of hydrogen cyanide. The list is not exhaustive.

Three methods for up to 50 mg/l: a photometric method with pyridine/barbituric acid, a titrimetric method using the Tyndall effect and a titrimetric method using an indicator.