Study of Stoichiometry of Ferric Thiocyanate Complex for Analytical Purposes Including F- - Determination

I. Hayder, Omed; M.Najib, Fadhil

	Study of Stoichiometry of Ferric Thiocyanate Complex for Analytical Purposes Including F- - Determination
Iraqi National Journal Of Chemistry
Article 1, Volume 0, Issue 42, 2014, Pages 135-155
Authors
Omed I. Hayder; Fadhil M.Najib
Abstract
Abstract The rather old and well known Fe(III)-thiocyanate system has been restudied. The stepwise mole ratio complexation between them has been carefully confirmed. A wavelength shift from 460 t0 480 nm has been observed by increasing SCN- ion concentration and remained constant at 480nm.where Fe(III): SCN- was 1:6. An improvement in the problem of stability of the complex has also been achieved by creating an oxidizing medium using 9.5x10-4 M KMnO4 , to prevent the inner redox reaction between SCN- and CNS . The stability has been improved from zero time to about 47 mins. Total iron has been determined in water and drugs down to 0.06ppm Fe3+ with r2 = 0.9997 ,recovery of 99.1-102% and precision of 0.13%. A hypsochromic shift from 480 to 410 nm. caused by the effect of fluoride ion was exploited for its indirect determination down to 0.019ppm F – .This concentration can be lowered even more than that obtained with fluoride ion selective electrode if standard addition method was used. The recovery of F – ion was between 105-95%, with C.V. 2%. This method was .used for the determination of F – ion in water and toothpaste and compared with the results obtained with fluoride ion-selective electrode using statistical treatments.
Keywords
Ferric thiocyanate system; Total Fe; III; indirect determination of fluoride

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