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    Rapid Identification of Metal Finishes

    Published: Jan 1950

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    A portable kit for the rapid identification of zinc, cadmium, lead, nickel, silver, tin, and chromium metals and plated metal finishes was developed during the war by Western Electric. This kit has found extensive use in inspection and sorting work and is now commercially available. The scheme of analysis employed consists of the electrolytic solution of a small quantity of metal into an electrolyte contained in a filter paper and the application of reagents to the paper to produce identifying colors. The kit, shown in Fig. 1, consists of: 1. Electrolysis circuit—two dry cells, a milliammeter, fixed 60-ohm resistance, cathode plate, and anode probe. 2. Bottles of Reagents equipped with medicine dropper. Electrolytes— Potassium chloride and potassium nitrate, Identifying Reagents—Sodium sulfide, potassium iodide, potassium chromate, silver nitrate, potassium ferrocyanide, uranium nitrate, and dimethylglyoxime. The sequence of analysis is outlined in Fig. 2. A small piece of filter paper is placed on the cathode plate and a few drops of potassium chloride solution, the first electrolyte, are added. The metal sample is placed on the paper and is contacted by the anode probe. Deflection of the needle on the milliammeter shows electrolysis is taking place. After a few seconds the probe and sample are removed and a few drops of sodium sulfide, the first reagent, are added to part of the moist filter paper. A yellow stain positively identifies cadmium. Lead, nickel, silver, and tin show a black stain while zinc and chromium fail to produce a stain.

    Author Information:

    Lewis, A.
    Western Electric Co., Inc., Kearny, N. J.

    Evans, D. R.
    Western Electric Co., Inc., Kearny, N. J.

    Committee/Subcommittee: E01.20

    DOI: 10.1520/STP47557S