Methodology
The analysis is an example of iodometry. A solution of iodine is yellow/brown in color and any chemical group (usually C=C double bonds) in the substance that reacts with iodine will discharge the yellow color. The amount of iodine solution thus required to keep the solution yellow/brown is a measure of the amount of iodine sensitive groups.
In a typical procedure, the fatty acid is treated with an excess of the Hanuš or Wijs solutions, which are, respectively, solutions of iodine monobromide (IBr) and iodine monochloride (ICl) in glacial acetic acid. Unreacted iodine monobromide (or monochloride) is then allowed to react with potassium iodide, converting it to iodine, whose concentration can be determined by titration with sodium thiosulfate.
The chemical reaction associated with this method of analysis involves formation of the diiodo alkane (R and R' symbolize alkyl or other organic groups):
The precursor alkene (RCH=CHR') is colourless and so is the organoidine product (RCHI-CHIR').
Read more about this topic: Iodine Value
Famous quotes containing the word methodology:
“One might get the impression that I recommend a new methodology which replaces induction by counterinduction and uses a multiplicity of theories, metaphysical views, fairy tales, instead of the customary pair theory/observation. This impression would certainly be mistaken. My intention is not to replace one set of general rules by another such set: my intention is rather to convince the reader that all methodologies, even the most obvious ones, have their limits.”
—Paul Feyerabend (1924–1994)