GB/T 4702.7-2016 in English

Background and significance of standard formulation

Metallic chromium is an important industrial material, and the accurate analysis of its chemical composition is of great significance to product quality and production process control. GB/T4702.7-2016 "Determination of nitrogen content in metallic chromium - distillation separation - Nessler reagent spectrophotometry" stipulates the determination method of nitrogen content in metallic chromium, which is applicable to the detection of nitrogen elements with a mass fraction range of 0.002%~0.150%. This standard is based on mature chemical analysis technology and combined with modern laboratory equipment requirements to ensure the accuracy and reliability of the results.

Comparison of standard framework and core content

Explanation of professional terms and practical application

Distillation separation method: The nitrogen element in the sample is converted into ammonia by heating, and it is separated from other components by the distillation process. Nessler reagent: It is used to detect the color reaction of ammonium ions and generate a blue-purple complex, which is suitable for spectrophotometer determination.

Case analysis: In actual detection, the nitrogen content of a metal chromium sample needs to be determined. According to the standard steps, 0.500g of the sample was weighed, dissolved, distilled and separated, and Nessler's reagent was added for color development. The absorbance value was measured to be 0.420. The corresponding nitrogen amount was found to be 18.5μg through the calibration curve, and the nitrogen content wN=0.0037% was calculated, which met the standard allowable error requirements.

Implementation suggestions and precautions

Equipment calibration: Ensure the accuracy of the spectrophotometer wavelength and calibrate the instrument performance regularly.

Reagent preparation: Prepare the reagents strictly in accordance with the standard requirements, especially Nessler's reagent, which needs to be left in the dark for 2 days before using the upper clear liquid.

Experimental environment: The laboratory temperature should be controlled at room temperature to avoid external interference affecting the measurement results.