Determination of halide is essential because of their detrimental property in certain compounds along with some beneficial properties. Usually halides are determined by argentometry (volumetric titration with AgNO3 soln with chromate as adsorption indicator). The disadvantage of this method is that sometimes end point detection becomes very difficult because of excessive precipitation of Ag halides during titration due to the interference that arises because of presence of other halides. In conductometric titration the detection of end point is very sharp and different halides react with AgNO3at difference conductance.
Usually halides are soluble in water except Ag+, Hg+, Pb++. In those cases, special dissolution processes are to be taken into consideration.
Estimation of chloride and iodide in mixture
KSP of Ag I = 1.7 X 10-16 mol2L-2
KSP of AgCl = 1.2 X 10-10 mol2L-2
So both of them are titrated with AgNO3. AgI will precipitate first. After consumption of all iodide ions, chlorides will interact with Ag+ ion. If conductance of the solution containing Cl– and I– are measured after addition of Ag+ in it (from burette) will get inflection. 1st one for the iodide and 2nd one for the chloride. Knowing the volume of Ag+ consumed, we can easily estimate the percentage of those ions present in the solution respectively. The following are the graphical representations as obtained during the conductometric titration of the chlorides and iodides in different proportions.
Table: A brief description of the recovery study as obtained from the Conductometric titration
Contributed by : Ms. Alakta Saha
Guided by : Prof. Barun Gupta