Neutralization

• Titrimetric/Volumetric Methods

  • Neutralization
  • Precipitation
  • Complexation
  • Oxidation-Reduction (REDOX)
• Chemical Reactions in Titrimetry

  • Neutralization (acidimetry and alkalimetry)
  • Precipitation
  • Complexation
  • Oxidation-reduction
• Oxidation-Reduction (REDOX) Reactions


  • Permanganate
  • Ceric sulfate
  • Iodimetry and iodometry
  • Bromine
  • Potassium iodate
  • Diazotization assay w/ nitrite
• Neutralization reactions


  Chemical processes in which an acid reacts with a base to produce water and salt
• Indicatorsof Neutralization

  Complex organic compounds used to determine endpoint, determine pH, and indicate a desired change in pH has been effected
• Indicators


  • May be weakly acids or weakly basic, capable of existing in 2 forms of different color that are mutually convertible
  • The usual concentration of indicator solution is 0.05%
  • From 0.1 to 0.2 mL of the indicator solution is used for 10 mL of liquid examined
  • Solutions of indicators of basic type and of the phthaleins are prepared by dissolving in alcohol
  • In preparing solutions of acid group, this must be neutralized with NaOH
  • Most of the indicators for acid - base titration are acidic
• Commonly used pH Indicators

  • Malachite green
  • Methyl Yellow
  • Bromophenol blue
  • Methyl Orange
  • Bromocresol green
  • Methyl red
  • Bromocresol purple
  • Bromothymol blue
  • Phenol red
  • Cresol red
  • Thymol blue
  • Phenolphthalein
  • Thymolphthalein
• Phenolphthalein


  • Approximate pH range for color change: 8.0-9.8
  • Color of acid form: clear
  • Color of base form: red-violet
• Methyl Red


  • Approximate pH range for color change: 4.4-6.2
  • Color of acid form: red
  • Color of base form: yellow
• Rules for the Use of Indicators

  • Use 3 drops of indicator TS unless otherwise directed
  • Strong Acid (SA) + Strong Base (SB) = use methyl orange, methyl red or phenolphthalein
  • SA + WB = methyl red
  • Weak Acid (WA) + SB = phenolphthalein
  • WA + WB = no indicator
• Indicator Papers

  • Lead acetate test paper
  • Litmus paper
  • Mercuric bromide test paper
  • Phenolphthalein paper
  • Potassium iodate-starch paper
  • Starch iodate paper
  • Starch iodide paper
  • Turmeric paper
• Acidimetry


  Direct or residual titrimetric analysis of BASES using an acid as titrant
• Types of Acidimetric Analysis

  • Direct titration = std. acid soln. from a buret into a soln. of base being assayed
  • Residual Titration = 1st vol. soln. (acid) is added in excess and the excess acid is titrated with std. base
• Alkalimetry


  The direct or residual titrimetric analysis of ACIDS
• Direct Alkalimetry


  Sample is acid, titrant is base
• Residual Alkalimetry


  Sample is acid, treated with excess standard base, titrated with acid
• Nonaqueous Titrimetric Analysis


  For substances that are poorly soluble and weakly reactive in water, make use of organic solvents, moisture must be avoided; 0.05% limit of moisture
• Solvents used in Nonaqueous Acidimetry


  • acetonitrile
  • alcohol
  • dioxane
  • benzene
  • chloroform
• Titrants used in Nonaqueous Acidimetry


  • perchloric acid in glacial acetic acid or dioxane
  • hydrogen bromide
• Example of Nonaqueous Acidimetry


  • Assay of methacholine chloride
• Indicators used in Nonaqueous Acidimetry


  • crystal violet
  • quinaldine red
  • naphtholbenzein
  • malachite green
  • methyl red
  • methyl orange
  • thymol blue
• Titrants used in Nonaqueous Alkalimetry

  • Na methoxide
  • Lithium methoxide
• Example of Nonaqueous Alkalimetry

  • Assay of phenytoin (organic acid)
• Indicators used in Nonaqueous Alkalimetry

  • azo violet
  • thymol blue
  • nitroaniline
  • thymolphthalein
  • hydroxyazobenzene