Iodimetric and iodometric titrations

Only freshly prepared starch solution should be used. Two millilitres of a 1 per cent solution per 100 mL of the solution to be titrated is a satisfactory amount the same volume of starch solution should always be added in a titration. In the titration of iodine, starch must not be added until just before the end point is reached. Apart from the fact that the fading of the iodine colour is a good indication of the approach at the end point, if the starch solution is added when the iodine concentration is high, some iodine may remain adsorbed even at the end point. The indicator blank is negligibly small in iodimetric and iodometric titrations of 0.05M solutions with more dilute solutions, it must be determined in a liquid having the same composition as the solution titrated has at the end point. 

What is the basic difference between iodimetric and iodometric titrations Explain with the help of equations involved in such typical titrations. 

Why are iodimetric titrations usually done in neutral solution and iodometric titrations in acid solution ... 

Colour transitions of indicators Acid-alkali and iodometric/iodimetric titration Pipetting technique... 

Determination of ozone in aqueous solution is perhaps the most problematic for a variety of reasons (1) ozone is unstable (2) ozone is volatile and easily lost from solution and (3) ozone reacts with many organic compounds to form products such as ozonides and hydrogen peroxide that are also good oxidants. Careful study of the use of iodometric methods for the determination of ozone in aqueous solution has revealed that the stoichiometric ratio of ozone reacted with iodine produced in the reaction varies from 0.65 to 1.5, depending on pFI, buffer composition and concentration, iodide ion concentration, and other reaction conditions. As a result, iodometric methods are not recommended. Ozone can be determined iodimetrically by addition of an excess of a standard solution of As(III), followed by titration of the excess As(III) with a standard solution of iodine to a starch endpoint. Methods using DPD, syringaldazine, and amperometric titrations have also been developed. 

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