A Study on Application of Negative Absorption spectrophotometry in Add Colour Spectrophotometry and Determination of Frac Ferrum

This paper makes a systematic study on application of negative absorption spectrophotometry in add colour photometry about chromogenic agent by colour compound and establishes dual wavelength spectrophotometry of positive and negative absorption that can determine real and signal absorbance of real absorption peak.This method applies in the field of this type photometric analysis,molar ratio determination of composition for chelate,and judgement of situation in chemical reaction and so on,the effect clearly superior to the traditional method and it can solve many questions which the latter fails to do,so it is of value both in theory and practive.In the samples of determining Fe 3+and Zn 2+ on contrast degree of wavelength 160 and 49nm respectively,the real absorption peak wavelengths of chelat formed are 560 and 461nm,the real absorption molar absorptivity(e r)are 1 70×104 and 2 10×105L.mol -1.cm -1,the signal molar absorptivity(e s)are 3 10×104 and 2 86×105L.mol -1.cm -1,the dates are 1 26,1 98,2 23 and 2 71 times than traditional method do.