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topic 1175

Testing free cyanide in cadmium plating wastewater


Just found your web site and found it very informative. I have sent in my membership fees to AESF and am waiting to hear from them.

My current problem is this. The shop I work in has just finished installing triple counter flowing rinses on 12 stations. It has made a very big difference. Our only problem at this time is we also purchased a cyanide destruct system and we are unable at this time to accurately determine the amount of free cyanide in our waste water. The test we use for our tank solution doesn't seem to be good enough for weaker concentration. The companies I've called have various test strips but they only work in a narrow range of concentrations. Some of the rinses have been in use for quite a while, but once we get this resolved we should be in good shape.

I would appreciate any help you can give me.

Will Burbage


My first question is why are you testing the rinses for cyanide?

If you want to know rinse purity get a $50 pocket conductivity meter. It can be used to check for more than just cyanide and only needs batteries once a year (no reagents to purchase). You can also do a pH check.

If you are checking for wastewater treatment effectiveness, strips will not do. It's better to just check for a chlorine residual with starch iodidi papers, which guarantees amenable cyanide is gone when the chlorine is positive.

A distillation according to standard EPA methods is necessary to get total cyanide in order to "absolutely" guarantee cyanide destruction..

If you still need strips, EM Science (Merck) has them in multiple ranges, but the best works from 0 to 30 mg/l. It actually requires mixing a small sample with reagents in a test tube, thern dipping the strip, but the wait is only a minute. I haven't used them for a couple of years, but they should still be available through a good lab supplier.

bill vins
Bill Vins
microwave & cable assemblies
Mesa (what a place-a), Arizona 


Test strips are not much more than yes or no (go or no go). they are limited in analytical ability. They also only react to free cyanide. You are probably going to have to test for total cyanide.

Frank Altmeyer has written several articles in AESF's magazine on problems with testing and EPA desires. If you have cyanide, I would try to get a copy of the last two years articles.

His company Scientific Control Laboratories, Inc. [Chicago, IL] may be able to help you also (for a fee).

James Watts
- Navarre, Florida

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