Hanna Instruments HI 96724C Instruction Manual

Contents

Hanna Instruments HI 96724C Instruction Manual Manual pdf 6 page image

6PRINCIPLE OF OPERATIONAbsorption of Light is a typical phenomenon of interaction between electromagnetic radiation andmatter. When a light beam crosses a substance, some of the radiation may be absorbed byatoms, molecules or crystal lattices.If pure absorption occurs, the fraction of light absorbed depends both on the optical path lengththrough the matter and on the physical-chemical characteristics of the substance according to theLambert-Beer Law:-log I/I o = ελ c dorA = ε λ c dWhere:-log I/I o = Absorbance (A)I o = intensity of incident light beamI = intensity of light beam after absorptionε λ = molar extinction coefficient at wavelength λc = molar concentration of the substanced = optical path through the substanceTherefore, the concentration "c" can be calculated from the absorbance of the substance as theother factors are known.Photometric chemical analysis is based on the possibility to develop an absorbing compoundfrom a specific chemical reaction between sample and reagents. Given that the absorption of acompound strictly depends on the wavelength of the incident light beam, a narrow spectralbandwidth should be selected as well as a proper central wavelength to optimize measurements.The optical system of Hanna's HI 96 series colorimeters is based on special subminiaturetungsten lamps and narrow-band interference filters to guarantee both high performance andreliable results.HI 96 series block diagram (optical layout)