Abstract
The automatic system (Fig. 1) consists of a sample changer, a dissolution vessel, a distillation vessel, a color reaction vessel, a spectrophotometer and a controller. The automatic determination of nitrogen in steel is performed according to predetermined dissolution (Fig. 4) and distillation-determination programs (Fig. 5). The chipped steel sample on the sample changer is transferred into the dissolution vessel by vaccum suction. Hydrochloric acid (13.23 ml), hydrogen peroxide (4.68 ml) and water (10.38 ml) are added into the vessel to dissolve the sample. Then hydrogen peroxide is decomposed by heating. The sample solution and washings (28.3 ml) are transferred into the distillation vessel, where acid-soluble nitrogen is distilled as ammonia by heating and bubbling after addition of a sodium hydroxide solution (40%, 24.20 ml). The ammonia is carried with air into the color reaction vessel through the condenser and absorbed in water circulating through the pipe (consisting of an air blowing pipe, a bubble remover, a flow cell and a drain valve). The absorbance of the solution is measured at 430 nm after addition of Nessler's reagent (4.08 ml). The analytical results of steel samples (Table 1. 2) were in good agreement with those obtained by the conventional manual method.
