The curve color of ammonia nitrogen is color. According to relevant data, the standard method of ammonia nitrogen analysis is mainly Nessler's reagent colorimetry. The drawing of the standard curve is to use different concentrations of ammonia nitrogen standard solution X, add chromogenic agent and measure the absorbance value Y, and then you can get the linear equation of y=bx+a, which is the mathematical expression of the curve. Then the absorption value of the sample is determined, and the concentration of ammonia nitrogen can be calculated according to this formula.