Zinc deposits are present in much of the earth's crust. The metal provides an effective protective coating for steel (galvanized coatings) and is used as an alloying agent in the production of brass and die castings. Zinc salts are useful as corrosion inhibitors in cooling water treatment formulations.  

The USEPA has established a Maximum Secondary Drinking Water Standard of 5 mg/L for zinc. Common sources of zinc are the deterioration of galvanized iron, dezincification of brass, and industrial pollution.

The Colorimetric Method. CHEMetrics' method determines soluble zinc in drinking water and wastewater. Zinc reacts with the reagent "zincon" in a buffered alkaline solution to form a blue complex. The intensity of the color developed is directly proportional to the concentration of zinc in the sample. Interference from other heavy metals can be eliminated by the addition of cyanide. However, for safety, cyanide has not been included in the reagent formulation. Results are expressed as ppm (mg/L) Zn.

Shelf-life. Although the reagent in the ampoule is stable, the indicator solution has a 5-month shelf-life. We recommend stocking quantities that will be used within 4 months. The indicator solution can be ordered separately.