Study of stoichiometry of ferric thiocyanate complex for analytical purposes including f-determination

الملخص EN

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 9.5 x 10-4 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.