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Chloride Analysis

Chloride Analysis. Chloride Methods. Gravimetric Chloride Potentiometric titration Visual Indicators Mohr Method Fajans Method Volhard Method. In all of these methods the chloride sample is dissolved & reacted with silver nitrate. Cl -1 + Ag +1  AgCl. Gravimetric Chloride.

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Chloride Analysis

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  1. Chloride Analysis

  2. Chloride Methods • Gravimetric Chloride • Potentiometric titration • Visual Indicators • Mohr Method • Fajans Method • Volhard Method

  3. In all of these methods the chloride sample is dissolved & reacted with silver nitrate Cl-1 + Ag+1 AgCl

  4. Gravimetric Chloride • Use a balance to measure mass • of sample and AgCl Precipitate • No endpoint detection

  5. Potentiometric Titration • Balance for mass of sample • Buret for volume of titrant added • pH meter with silver electrode for end-point detection

  6. Mohr Method • Balance for mass of sample • Buret for volume of titrant added • Indicator for endpoint detection Na2CrO4

  7. Mohr Method Cl-1 + Ag+1 AgCl Ksp =1.82 x 10-10 CrO4-2 + 2Ag+1 Ag2CrO4(brick red) Ksp =1.2 x 10-12 • Must titrate a blank and subtract from total volume of silver nitrate added

  8. Fajans Method • Balance for mass of sample • Buret for volume of titrant added • Indicator for endpoint detection Fluorescein- Adsorption Indicator

  9. Fajans Method Fluorescein

  10. Fajans Method HFl  H+1 + Fl-1(yellow green)

  11. Cl-1 Cl-1 AgCl Ag+1 Ag+1 Cl-1 Ag+1 Cl-1 AgCl Cl-1 Ag+1 Ag+1 Fajans Method Cl-1 + Ag+1 AgCl Chloride titrated with silver nitrate AgFl Red Color Colloidal ppt Before eq pt

  12. Volhard Method • Indirect Method – Back titrate excess Ag+1 • Add excess silver nitrate • Ag+1 + Cl-1  AgCl(s) (white ppt) + Ag+1 • Excess Ag+1 is titrated with standardwith standard potassium thiocyanate. • SCN-1 + Ag+1  AgSCN(s) • Fe+3 indicator • Fe+3 + SCN-1  Fe(SCN)+2 (red ppt)

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