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ASTM Committee D-19 on Water has recently published a method for the determination of free cyanide in water and wastewater by microdiffusion. This method (ASTM Method for the Determination of Free Cyanide in Water and Wastewater by Microdiffusion [ASTM D 4282-83]) is based on adjusting a sample in a microdiffusion cell to pH 6.0. All cyanides present that can form hydrogen cyanide (HCN) are defined as free cyanide by this method. The HCN is allowed to diffuse for 4 h into the center chamber of the microdiffusion cell, which contains sodium hydroxide. The cyanide ion thus formed is chlorinated and then reacted with pyridine-barbituric acid. A colorimetric measurement is made to determine the cyanide level. The round robin data obtained show percent biases of −1.9, −5.0, and −4.2% at concentrations of 32, 80, and 144 μg/L of CN−, respectively, in Reagent Type II water. Data are shown from the original investigation that established the method parameters. Additional pertinent work is documented.
Technical associate, Eastman Kodak Co., Rochester, NY
Stock #: JTE10769J