The pH range over which the ferrous derivatives are stable, extends farther into the alkaline range than for the parent 1,lO-phenanthroline, approximately pH 11 in contrast to 9; this may prove of interest in some circumstances. As colorimetric reagents for iron these reagents then have no advantage over 1,lO-phenanthroline in sensitivity, but they do have the definite merit that they can be used in perchlorate solutions. Ferrous tris(1,lOphenanthroline) perchlorate is insoluble and following wet ashing with perchloric acid or the precipitation of protein with perchloric acid, perchloric acid must be removed by evaporation with sulfuric acid before the iron may be de-
termined. This step is not necessary with the new sulfonated reagents. Sulfonation of 1,lO-phenanthroline raises considerably the potential a t which the ferrous derivative is oxidized to the ferric derivative, Table I. As indicators, the ferrous derivatives of both the 5- and 3-sulfonic acid give vivid and sharp color changes. Both are somewhat more sensitive to acid than the parent ferroin, but the 5sulfonic derivative is sufficiently stable to function well as an indicator in strong acids. Both indicators have the advan$age over ferroin that they can be used in perchloric acid solutions. They are ideal for titrations with quadrivalent cerium in either sulfuric or perchloric acid solutions.
A C K N O W LEDGMENl
The authors express their appreciation of grants of chemicals from the G. Frederick Smith Chemical Co., Columbus, Ohio. LITERATURE CITED
(1) Blair, D. E., Diehl, H., Talanfu 7,
163 (1961).
(2) Case, F. H., Catino, S., Scholnick, F.,J. Org. Chem. 19,31 (1954).
(3) Smith, G. F., Cagle, F. W., Jr., Zbid., 12, 781 (1947). (4) Zacharias, D. E., Case, F. H., unpublished work. RECEIVED for review January 3, 1961. Accepted March 6, 1961.
Improved 2-Thenoyltrifluoroacetone Extraction Method for Radiozirconium S. FREDRIC MARSH, WILLIAM J. MAECK, GLENN L. BOOMAN, and JAMES E. REIN Atomic Energy Division, Phillips Petroleum Co., Idaho Falls, Idaho
b An improved method for the determination of radiozirconium, based on the 2-thenoyltrifluoroacetone (TTA) extraction, is described. A fluoride pretreatment converts hydrolytic and colloidal species of zirconium to a form extractable, as the TTA complex, into xylene. Radioiodine, the only fission product significantly extracted with zirconium, is separated in
