anachem sas 6

• Volumetric method of analysis

  Analytical methods in which the volume of a solution of known concentration consumed during an analysis is taken as a measure of the amount of active constituent in a sample being analysed
• Analyte


  The chemical substance being analysed
• Titrant


  The solution of known concentration added during a titration
• Titration


  The act of adding and measuring the volume of titrant used in the assay
• End point


  The point at which there occurs a sudden change in some property of the reaction mixture, a change which is made apparent by use of indicators or electrometrically
• Equivalence point


  The theoretical point at which equivalent quantities of analyte and titrant have reacted
• Gram equivalent weight (GEW)

  The weight in grams which is chemically equivalent to 1 gram-atom of hydrogen (1.0079)
• Gram-miliequivalent (meq)


  The number of gram-miliequivalents involved in a quantitative procedure
• Standardization


  The determination of the normality or molarity of a solution
• Primary standard


  A carefully weighed sample of a substance of known purity
• Secondary standard


  Another standard solution used to standardize a solution
• Glassware used in volumetric determination

  • Buret
  • Pipet
  • Volumetric flask
  • Erlenmeyer flask
• Neutralization titration


  1. Titration of a strong acid with a strong base

  2. Titration of a weak acid with a strong base

  3. Titration of a weak base with a strong acid
• Indicators


  • Naturally occurring and synthetic compounds that exhibit colors that depend on the pH of the solutions in which they are dissolved
• Indicators


  • Malachite green
  • Methyl yellow
  • Bromophenol blue
• Results in drug assays are usually expressed in terms of % w/w, % w/v and % v/v as described in the official compendiums
• Standard solutions of bases are usually prepared from solid sodium, potassium, and occasionally barium hydroxides
• Many naturally occurring and synthetic compounds exhibit colors that depend on the pH of the solutions in which they are dissolved
• Some substances have been used for centuries to indicate the acidity or alkalinity of water, and are still applied today as acid/base indicators
• List of common indicators and the color they emit

  • Malachite green (Yellow/Green)
  • Methyl yellow (Red/Yellow)
  • Bromophenol blue (Yellow/Blue)
  • Methyl orange (Pink/Yellow)
  • Bromocresol green (Yellow/Blue)
  • Methyl red (Red/Pink/Yellow)
  • Bromocresol Purple (Yellow/Purple)
  • Bromothymol blue (Yellow/Blue)
  • Phenol red (Yellow/Red)
  • Cresol red (Yellow/Red)
  • Thymol Blue (Yellow/Blue)
  • Phenolphthalein (Colorless/Red/pink)
  • Thymolphthalein (Colorless/Blue)
• Use 3 drops of indicator test solution for a titration unless otherwise directed
• Rules for the use of indicators


  • When a strong acid is titrated with a strong alkali, or a strong alkali with a strong acid, methyl orange, Methyl red or Phenolphthalen may be used
  • When a weak acid is titrated with a strong alkali, use phenolphthalein as the indicator
  • When a weak alkali is titrated with a strong acid, use methyl red as the indicator
  • A weak alkali should never be titrated with a weak acid, or vice versa, since no indicator will give a sharp end point
  • The appearance of a color is more easily observable that is the disappearance. Therefore, always titrate where possible to the appearance of a color
• Neutralization titrations are widely used to determine the concentration of acidic or basic analytes or analytes that can be converted to acids or bases by suitable treatment
• Water is the usual solvent for neutralization titrations because it is convenient, inexpensive, and nontoxic
• Some analytes cannot be titrated in aqueous media because of low solubility or because their strengths as acids or bases are not large enough to give satisfactory end points. Such substances can often be titrated by nonaqueous solvents
• In volumetric precipitemetry a class of reaction is dealt with that require the formation of relatively insoluble substances or precipitates to cause the reactions to go to sufficient completion to be quantitative in nature
• Determination for precipitation reaction end point

  • Cessation of precipitation or the appearance of turidity
  • Use of internal indicators
  • Instrumental methods i,e. Potentiometric or amperoemtric
• Indicators for the volumetric precipitation

  • Ferric ammonium sulphate (appearance of red color marks)
  • Potassium chromate (Red precipitate)
  • Dichloroflurescein (DCF)
  • Eosin Y
  • Tetrabromophenolphthalein ethyl ester
• Historically, the quantitative analysis of inorganic products containing metal ions such as Al, Bi, Ca, Mg, and Zn was performed using gravimetric methods
• With the introduction of the analytical reagent Disodium ethylenediaminetetraacetate, commonly referred to as EDTA, a new volumetric procedure evolved for metal determination employing metal ions indicators in the same manner that pH indicators are used in acid-base titrations
• Complex


  A compound formed when a metal ion combines with a molecule which can donate electrons
• Chelate


  A complex in which the combining molecule contains two or more groups that donate electrons
• EDTA will react with metal ions to from water soluble, stable complex, or chelate compound
• The reaction of EDTA with metal ions is rapid and quantitative with such polyvalent metal ions as Aluminium, bismuth, calcium, cupper, Mercury, Magnesium and Zinc
• Monovalent ions yield relatively weak or unstable complexes with EDTA
• In an oxidation/reduction reaction electrons are transferred from one reactant to another
• A substance that has a strong affinity for electrons, such as Ce4+, is called an oxidizing agent, or an oxidant
• A reducing agent, or reductant, is a species, such as Fe2+, that donates electrons to another species
• Oxidation/reduction reactions can be viewed in a way that is analogous to the Brønsted-Lowry concept of acid/base reactions
• When a reducing agent donates an electron, it becomes an oxidizing agent that can then accept an electron