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Visible Spectrophotometer

Visible Spectrophotometer. Visible Spectrophotometer. Visible Spectrophotometer. 100 % Adjust. I 0. I. white light. detector/recorder. 100 % adjust blank distilled water. prism. I 0 = I % transmittance = (I / I 0 ) x 100 = 100 absorbance = 0. Visible Spectrophotometer.

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Visible Spectrophotometer

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  1. Visible Spectrophotometer

  2. Visible Spectrophotometer

  3. Visible Spectrophotometer 100 % Adjust I0 I white light detector/recorder 100 % adjust blank distilled water prism I0 = I % transmittance = (I/ I0) x 100 = 100 absorbance = 0

  4. Visible Spectrophotometer Zero Adjust I0 I white light detector/recorder zero adjust (barrier inserted) prism I = 0 % transmittance = 0 absorbance = maximum

  5. Visible Spectrophotometer Sample I0 I white light detector/recorder sample solution prism I < I0 % transmittance = (I/ I0) x 100 = 50% absorbance = 1.7

  6. Visible Spectrophotometer I0 I white light detector/recorder sample solution prism I0 = I % transmittance = (I0 / I) x 100 = 100 absorbance = 0 In order for blue solution to absorb light, wavelength must be changed to blue’s complement

  7. Visible Spectrophotometer white light I0 I detector/recorder sample solution prism Wavelength is changed by either rotating prism or position of slit

  8. “Spec 20” Visible Spectrophotometer digital analog

  9. 1. Adjust wavelength

  10. 2. Zero adjust with sample compartment empty : 0 % T

  11. 3. 100 % adjust with distilled water (blank) in sample compartment : 100% transmittance

  12. 4. Record sample absorbance (Be certain to switch MODE to absorbance)

  13. Beer’s Law • As the intensity of the color of the sample solution increases… • the absorbance increases. • A =  b c absorbance constant path length concentration

  14. Determination of the Concentration of an Unknown Solution • Prepare a set of standard solutions of known concentrations • Select the appropriate wavelength • Determine the absorbance of each • Determine the absorbance of the unknown solution

  15. Sample Conc.(ppm) Absorbance 1 0.0 0 2 5.0 .0023 3 10.0 .0045 4 15.0 .0056 5 20.0 .0076 Unknown ? .0051

  16. 13 ppm

  17. C = Recall Beer’s Law: A =  b c + 0 y = mx + b .0051 = 0.00037 x C + 0.00030 = 13.0

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