BS 6068-2.18:1986

Foreword
Method
0. Introduction
1. Scope and field of application
2. Definition
Subsection one: Liberation and absorption of hydrogen
cyanide
3. Principle
4. Reagents
5. Apparatus
6. Sampling and samples
7. Procedure
Subsection two: Determination of cyanide ions - Photo-
metric method with pyridine/barbituric acid
8. Applicability
9. Principle
10. Reagents
11. Apparatus
12. Procedure
13. Expression of results
14. Precision
15. Test report
Subsection three: Determination of cyanide ions - Titri-
metric method using the Tyndall effect
16. Applicability
17. Principle and reactions
18. Reagents
19. Apparatus
20. Procedure
21. Expression of results
22. Precision
23. Test report
Subsection four: Determination of cyanide ions - Titri-
metric method using an indicator
24. Applicability
25. Principle
26. Reagents
27. Apparatus
28. Procedure
29. Expression of results
30. Test report
Tables
1. Interferences
2. Precision data (photometric method)
3. Precision data (titrimetric method)
Figures
1. Apparatus for separation of hydrogen cyanide by
    stripping
2. Apparatus for determination of cyanide ions using
    Tyndall effect
Bibliography

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.

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.