cyanides, the following stock solutions should be prepared: 10% aqueous sodium hydroxide (solution A), 10% aqueous ferrous sulfate (solution B), and 5% ferric chloride (solution C). Mix 2 mL of the sample with 1 mL of distilled water and 1 mL each of solutions A, B, and C. Add enough concentrated sulfuric acid to make the solution acidic. Development of a blue color (Prussian blue, from ferric ferrocyanide) indicates cyanide. Because of the toxicity of the hydrogen cyanide formed during this test, only a small sample should be tested, and appropriate ventilation should be used.
Presence of halogen. Heat a piece of copper wire until red in a flame. Cool the wire in distilled or deionized water, and then dip the wire into the unknown. Again heat the wire in the flame. The presence of halogen is indicated by a green color around the wire in the flame.
An important question for planning within the laboratory is whether or not a waste is regulated as hazardous, because regulated hazardous waste must be handled and disposed of in rather specific ways. This determination has very important regulatory implications, which can lead to significant differences in disposal cost. The Environmental Protection Agency