RAPID METHOD FOR DETERMINING NICKEL ON THE SURFACE OF ENAMELING IRON*

A photometric method for determining nickel on nickel-coated steel is described. The method is very rapid, requiring less than 5 minutes. The standard deviation (σ) has been found to be 0.0028 gm. of nickel per sq. ft. when testing a sheet carrying 0.10 gm. of nickel per sq. ft. The sample is obtained by dissolving the nickel coating on a small area with dilute nitric acid. The nitric acid is confined by using a weighted rubber ring and is withdrawn by suction into a 200-ml. Erlenmeyer flask marked at 200 ml. A large excess of ammonium hydroxide is added, followed by ammonium persulfate and dimethylglyoxime. The solution is diluted to 200 ml. with water. After filtering off the ferric hydroxide, the intensity of the red color, which is proportional to the amount of nickel present, is measured by means of a photoelectric photometer.