Talantn. 196.5. Vol. 12. pp. 649 to 650.
Pergamon Press Ltd.
Printed in Northern Ireland
LETTERS TO THE EDITOR
Use of iron(III)-l,lO-phenantbroline complex in presence of light as an oxidising agent in organic analysis SIR,
The oxidising properties of the yellow complex of l,lO-phenanthroline with iron(lI1) have been used for the indirect determination of cobalt1-4 and of uranyl ions. 6 An indirect determination of The yellow iron (III)oxalic acid using ferron has been described by Burrow9 and Jablonkowski.’ 1,lO-phenanthroline complex is photosensitive, especially after irradiation with light having a wavelength shorter than 590 nm.8 In the presence of organic acids with labile carboxyl groups it is possible to make use of the catalytic influence of light on the reaction: [Fe,Phen,
(OH),]*+ + 2e + 2 HPhen+ -, 2[FePhen#+
+ 2 H,O.
In solutions containing 3.7 x lo-“M iron(II1) (as chloride), 7 x lo-‘M l,lO-phenanthroline, 0.6M sodium acetate, 0.6M ammonium chloride and 04X1.0 mg of citric, tartaric, malic or oxalic acid in 100 ml, decomposition of the organic acids takes place after irradiation in accordance with the following equations: [Fe,Phen, [Fe,Phen,
+ (COO),*- + 2 HPhen+ -%
f 2 R.CHOH.COO-
2IFePhen,]*+ + 2 CO, + 2 H,O
+ 2 HPhen+ -%2[FePhen,]‘+
C 2 R.CH*OH f2 CO1 + 2 HyO.
As a proof of the liberation of carbon dioxide, a stream of argon was first bubbled through the illuminated solutions of the organic acids under the above conditions, then through a solution of barium chloride; a precipitate of barium carbonate was formed in the latter solution. In samples containing no other substances interfering with the properties of iron-phenanthroline complexes, it is possible to make use of the mentioned oxidising effect for the determination of the stated acids. The composition of a test sample and of the solution used for plotting the calibration curves must contain a sufficient excess of the yellow iron(III)-l,lO-phenanthroline complex (at least 25%). Furthermore, it is necessary to maintain constant conditions of irradiation and temperature. JOSEF NOVAK
Institute of Physics Academy of Sciences Prague, Czechoslovakia 12 November 1964. REFERENCES r F. Vydra and R. Piibil, Talanta, 1959, 3, 103. a Idem, ibid., 1960, 5,44. s Idem, Acta Chim. Acad. Sci. Hung., 1961, 28, 297. 4 Idem, CON. Czech. Chem. Comm., 1961,26,3081. 6 Zdem, Talanta, 1962,8, 1009. a S. Burrows, Analyst, 1950, 75, 80. ’ W. Jablonkowski, Chem. Analit., 1964,9,683. BJ. Novak and H. Arend, Talanta, 1964,11, 898. 649