How can a sample containing sulfides be pretreated for cyanide testing?

Document ID

Document ID TE1214

Published Date

Published Date 27/05/2017
Question
How can a sample containing sulfides be pretreated for cyanide testing?
Summary
Treating cyanide samples for sulfides
Answer
Sulfides present in cyanide samples will create thiocyanate. To treat a sample for sulfides prior to testing, use the following procedure:

Sulfides
To test for and remove sulfide, pretreat the sample as follows:
1. Put a drop of sample on a disc of hydrogen sulfide test paper that has been wetted with pH 4 buffer solution.

2. If the test paper darkens add a 1-g measuring spoon of lead acetate to the sample and repeat step 1.

3. If the test paper continues to turn dark add lead acetate until the sample tests negative for sulfide.

4. Filter the lead sulfide precipitate. Preserve the sample for storage with 5 N sodium hydroxide standard solution or neutralize to a pH of 7 for analysis.