In the colorimetric dimethylglyoxime method for nickel which employs persulfate oxidation, the usual practice has been to make the solution "slightly ammonlacal" by addition of 1:1 ammonium hydroxide, followed by addition of 0.1 g of ammonium persulfate (estimated with a spatula). Considerable difficulty has been reported with this procedure with respect to adjustment of basicity and precipitation of nickelous dlmethylglyoximate. The solution soon became cloudy and a red precipitate settled out upon standing in a matter of 15 to 30 minutes, which precluded any spectrophotometric measurements.
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