ANALYSISFINALS

• Volumetric apparatus


  More accurate to use than Erlenmeyer flasks, Beakers, and other apparatuses used in measuring liquids
• Two types of volumetric apparatus

  • Apparatuses made to deliver a definite volume of liquid
  • Apparatuses made to contain a definite volume of liquid
• Burets


  • Graduated glass tubes of uniform bore throughout the whole length
  • Used in the measurement of variable quantities of liquids
  • Graduated into millilitres as the official unit of capacity
• Pipettes


  • Should be graduated to deliver at standard temperature the volume indicated
  • Two types: Transfer pipette and Measuring pipette
• Volumetric flasks


  • Standard measuring flasks calibrated to contain the indicated volume at 25 degrees C when filled to the mark
  • Used to prepare a standard solution
• Indicators


  Complex organic compounds used to determine end points in neutralization process, determine hydrogen-ion concentrations, and indicate a desired change in pH has been affected
• Theories to explain the change in color of indicators

  • Physicochemical/Physical theory
  • Organic theory
  • Colloidal theory
• Rules for the use of indicators

  1. Use 3 drops of indicator test solution for a titration unless otherwise directed

  2. When a strong acid (sample) is titrated with a strong alkali (titrant) or vice versa, methyl orange, methyl red, or phenolphthalein may be used

  3. When a weak acid (sample) is titrated with strong alkali (titrant), use phenolphthalein as the indicator

  4. When a weak alkali (sample) is titrated with a strong acid (titrant), use methyl red as the indicator

  5. A weak alkali (sample) should never be titrated with a weak acid (titrant) or vice versa since no indicator will give a sharp end point

  6. The appearance of a color is more easily observable than is the disappearance, therefore always titrate where possible to the appearance of a color
• Mixed indicators


  Used when indicators do not give sharp color changes, to sharpen up the color change
• Mixed indicators


  • Xylene cyanol + Methyl orange
  • Bromocresol green + Methyl red
  • Bromocresol green + Chlorophenol red
  • Cresol red + Thymol blue
  • Thymol blue + Phenolphthalein
• Chemical reactions used in titrimetry

  • Neutralization (Acid-Base) in Aqueous and Non-Aqueous Solvents
  • Oxidation-Reduction
  • Precipitation
  • Complexation
• Neutralization


  Chemical process in which an ACID (proton donor) reacts with a BASE (proton acceptor)
• Acidimetry


  The direct or residual titrimetric analysis of bases using an accurately measured volume of ACID
• Nitrogen determination by the Kjeldahl method

  1. Macro method: Ammonia is distilled into excess boric acid solution

  2. Semi-micro method: Smaller samples are employed using semi-micro Kjeldahl Apparatus
• Alkalimetry


  The direct or residual titrimetric analysis of acids using an accurately measured volume of ALKALI
• Aspirin hydrolysis products


  Acetic acid<|>Salicylic acid
• Sample substances for acidimetry in non-aqueous solvents

  • Amine
  • Amine salts
  • Heterocyclic nitrogen compounds
  • Alkali salts of organic acids
  • Alkali salts of weak inorganic acid
  • Amino acids
• Solvents for acidimetry in non-aqueous solvents

  • Neutral solvents: Acetonitrile, alcohols, chloroform, benzene, dioxane, ethyl acetate
  • Acid solvents: Formic acid, glacial acetic acid, propionic acids, acetic anhydride, sulfonyl chloride
• Titrants for acidimetry in non-aqueous solvents


  Perchloric acid in glacial acetic acid
• Indicators for acidimetry in non-aqueous solvents

  • Crystal violet, methylrosaniline chloride, quinaldine red, α-naphtholbenzein, malachite green
• Sample substances for alkalimetry in non-aqueous solvents

  • Acid halide
  • Anhydrides
  • Acids
  • Amino acids
  • Enols such as barbiturates
  • Imides
  • Phenols
  • Pyrroles
  • Sulfonamides
  • Organic salts of inorganic acids
• Solvents for alkalimetry in non-aqueous solvents

  • Ethylenediamine, n-butylamine & morpholine
  • Dimethylformamide and pyridine
• Titrants for alkalimetry in non-aqueous solvents

  • Sodium methoxide, lithium methoxide, sodium aminomethoxide, sodium triphenylmethane (for phenols & pyrroles)
  • Potassium methoxide (not used as it may produce a gelatinous product)
• Indicators for alkalimetry in non-aqueous solvents

  • Azo violet (for weak acids)
  • Thymol blue (for intermediate to strong acids)
  • Thymolphthalein
  • p-hydroxyazobenzene
• Precipitation volumetric precipitimetry


  Deals with the reaction that require the formation of relatively insoluble substances or precipitates to cause the reaction to go to sufficient completion
• Methods for determining the endpoint in precipitation

  • Cessation of the precipitation or the appearance of a turbidity
  • Use of internal indicators
  • Instrumental methods such as potentiometric and amperometric
• Indicators for precipitation


  • Ferric ammonium sulfate T.S. (endpoint: red color of ferric thiocyanate)
  • Potassium chromate T.S. (endpoint: red color of silver chromate against a white of silver chloride)
• Adsorption indicators


  • Dichlorofluorescein (DCF)
  • Eosin y T.S. or Tetrabromofluorescein
  • Tetrabromophenolphthalein ethyl ester (TEE)
• Standard solutions for precipitation

  • 0.1N Silver Nitrate
  • 0.1N Ammonium thiocyanate
• Argentometric methods


  Interaction between Silver Nitrate and Sodium Chloride: NaCl + AgNO3 → AgCl + NaNO3
• Parameters considered in argentometric methods

  • Precipitate formed must be insoluble
  • Precipitation process should be fast & rapid
  • Co-precipitation effects must be minimal
  • Detection of equivalence point must be apparently visible
• Categories of argentometric methods

  • Direct titration with Silver Nitrate
  • Ammonium Thiocyanate Silver Nitrate Titration (VOLHARD METHOD)
• Fajan introduced the precipitation method and the use of 0.1N AgNO3 as the Titrant & Potassium chromate as the Indicator (MOHR)
• Complexation method


  Quantitative analysis of inorganic pharmaceutical products containing metal ions such as Al, Bi, Ca, Mg, Zn
• Monovalent metals produce a weak and unstable complex when using the complexation method, so plane spectroscopy method is used instead
• Argentum


  Latin name of Silver (Ag)
• Interaction between Silver Nitrate and Sodium Chloride

  NaCl + AgNO3→AgCl + NaNO3
• Parameters considered


  • Precipitate formed must be insoluble
  • Precipitation process should be fast & rapid
  • Co-precipitation effects must be minimal
  • Detection of equivalence point must be apparently visible
• Categories of Argentometric Methods

  • Direct titration with Silver Nitrate
  • Ammonium Thiocyanate Silver Nitrate Titration (VOLHARD METHOD)
• FAJAN


  Introduced Precipitation method