SELECTIVE MERCURIMETRIC TITRATION ASSAY OF CHLORIDE CONCENTRATION IN THE WATER OF GREEN COCONUTS USING NOVEL INDICATOR SYSTEM

摘要

Objective: A selective mercurimetric titration procedure is proposed for the assay of chloride concentration in the water of green coconut using mercury(II) nitrate [(Hg(NO3)2] reagent and iron(III) nitrate [Fe(NO3)3] with synthetically prepared mercury(II) thiocyanate [Hg(SCN)2] indicator system. Methods: An indicator solution was prepared by titrating Hg(NO3)2 against potassium thiocyanate (KSCN) till a red color end point using Fe(NO3)3. Then a known amount of Hg(NO3)2 was added to indicator solution and titrated against the water of green coconut till the original red color reappeared. Results: The concentration of chloride present in the volume of coconut water utilized in between these two end points was found to be reacting in the 2:1 stoichiometric ratio with the Hg(NO 3 ) 2 taken in the second step of the titration. The statistical treatment of the experimental data obtained by using standard solutions of sodium chloride (NaCl) indicates that the procedure is precise and accurate. The phosphate, sulfate, organic compounds and inorganic minerals present in the coconut water did not interfere with the measurement of chloride by this procedure. Both the cationic mineral value (was also determined by complexometric titration) and chloride concentration in the coconut water were found to be decreased with the development of the coconuts. Conclusion: The proposed procedure of determination of chloride concentration in the water of green coconut is simple, reliable and inexpensive. This procedure is excellent for determination of chloride in the acidic solution without precise adjustment of the pH for detection of the end point. Owing to the homogenous reaction condition no titration errors those are commonly encountered by co-precipitation in the argentometric assay of chloride.