Abstract
The spectrophotometric method for the determination of ammonia nitrogen with thymol which had been established by the authors for uranium metal and its compounds was successfully applied to as low as 3 ppm of nitrogen in zirconium and zircaloy.
Satisfactory results were obtained in the analysis of the NBS zircaloy-2 standard and other samples. Twenty milligrams of tin, 3 mg of iron, 4 mg of nickel, . 2 mg of chromium and 0.2 mg each of aluminum, copper, silicon and titanium did not interfere. The molar absorptivity was the same as that previously reported (1.15× 104 at 670 mμ).
In the recommended procedure, up to 0.8 g of a sample was dissolved with 2 ml of sulfuric acid (18 N), 3 ml of hydrochloric acid and 5 ml of fluoboric acid (10%) by heating on a water bath. After dissolution, 1 ml of hydrogen peroxide solution (30%) was added to oxidize iron and the solution was then evaporated to almost dryness to remove the excess peroxide and acids. The residue was dissolved with 50 ml of water, and 20 ml of sodium citrate solution (25 w/v%) was added. After adjusting the pH of the solution to 9.8 10.3, 0.5 ml of sodium hypochlorite solution containing 0.3% of active chlorine was added with stirring. After 20seconds, 2.5 ml of a freshly prepared mixture of equal volumes of thymol solution (10% in acetone) and sodium hydroxide solution (1 N) was added. Sodium hydroxide solution (6 N) was then added to dissolve the deposited thymol, and the pH of the solution was adjusted to 11.6 11.9 with sodium phosphate solution (0.05 N) and sulfuric acid (6 N). Four milliliters of acetone was added and the resultant solution was diluted to 100 ml with water. After standing for 1.5 hours in darkness, the absorbance of the colored solution was measured against the blank at 670 mμ.
