Letter 4101

Easy system to detect Zinc metal, 0-250 ppm 

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I'm looking for a "quick test" for zinc metal, 0-250 ppm. Also any copper metal testers for the same parameters. Possibly a test paper system... accuracy is the key. If anyone can recommend highly a system, that would be great.

Keith Miller  
- DeKalb, Illinois

"Accuracy is the key". Ah, therein lies the rub, eh? The primary reason that more exotic methods like AAS are often used is that the accuracy of other methods is very questionable in wastewater which may have all sorts of interfering contaminants and reactions, and wherein some of the metal may be dissolved as a salt and some precipitated.

Test papers won't work because it is necessary to 'digest' (redissolve) the precipitated metal before you can learn anything at all.

There is a detailed report "The Performance of Analytical Test Kits on Metal Finishing Wastewater Samples" by Frank Altmayer & John Ruf, Feb. 87, which may be available from AESF or NAMF. It will tell you with cold hard numbers which test kits work best, as well as provide some subjective impressions on ease of use, etc.

But the bottom line is that the best you can hope for with test kits is repeatable results which you can correlate with AAS tests to determine what offsets and multipliers you need to use to project the real concentrations from the readings you get on your own wastewater.

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Keith - Is zinc the only metal that could/should be present? I'm also assuming that the 250 ppm is your upper range. Anyway, a quick & easy test for concentrations as low as .25 ppm is to use a 10% solution of 40% DTC. take a small sample of the effluent (5-10 ml) and add a few drops of the DTC solution. Zinc will show as a white color to the sample. Nickel will show as greenish white, and copper will give a tea color. Other metals will show as an off-white. Hope this helps get you started.

Good Luck.

Dan Brewer
chemical process supplier - Gurnee, Illinois