Sept. 5, 1961
3719
COMMUNICATIONS TO THE EDITOR
aqueous media) exhibits remarkable stability in 1.5 M ammonium or alkali fluoride.1° Such Am(1V) Lactogenic solutions show self-reduction a t a rate of approxiactivity mately 470’hour due to the alpha activity of Preparation I.U./mg. I t was hoped that tetravalent curium Starting material could be stabilized sufficiently by high fluoride (3 components) 20 0.75 + 4 concentrations to be observed in solution. 4 few Component I 30-35 0.75 $15 milligrams of Cm244had been brought to a high deComponents I1 and I11 5-10 0.75 - 1 gree of purity from stocks made available to us by When the temperature was maintained a t -20’ the Argonne National Laboratory. The specific during the initial preparation of starting material activity of Cm244is about 25 times that of Am241 from sheep pituitaries, our product contained a and one would predict a self-reduction rate for considerably greater proportion of component I Cm(1V) of 1-2% minute. However, by using than when the temperature was held a t 5’. Also, reasonably fast techniques, some 30-40 minutes highly purified component I can be converted easily should be available for spectral studies. into 3-component material upon standing in 2% In the americium(1V) work, a compound conaqueous NH40H a t 5’ for two hours. taining americium already in the tetravalent state The data obtained thus far indicate that com- was used as a starting material, i.e., Xm(OH), ponent I is biologically highly active prolactin, was dissolved in 15 Jf ammonium fluoride. Altwhereas components I1 and I11 seem to be altered tempts to make Crn(OH), by alkaline oxidation of forms of this component. Cm(OH)3using hypochlorite or ozone were not sucAcknowledgment.-The authors wish to thank cessful. Therefore dissolution of CmF4 (prepared Dr. il. Segaloff for the crop-sac-stimulating assays, under anhydrous conditions) was attempted. and Dr. D. E. n’illiams and Miss V. J. Powell for Curium tetrafluoride was prepared by treating the physical chemical measurements. CmF3 with elemental fluorine using methods and apparatus previously described.’l,l 2 Addition of (10) 0. Riddle, R . W. Bates and S. W. Dykshorn, A m . J . Physiol., lOS, 191 (1933). the resulting CmF4 to 15 -11 ”IF, either a t 25 or MERCKSHARP& DOHME RALPHA. REISFELD O’, produced only vigorous bubbling accompanied L.TONG RESEARCH LABORATORIES GEORGE EDWARD L. RICKES by the immediate formation of white CmF3 from NORMAX G. BRINK the yellow CmF4. We believe that the Cm(1V) is oxidizing NH4+under these conditions. MERCKISSTITUTEFOR THERAPEUTIC RESEARCH SANFORD KAHWAY, SEW JERSEY L. STEELMAN However, upon addition of CmF4 to 15 -IT CsF at RECEIVED JUNE 7, 1961 O‘, a solution of tetravalent c u r i u m a s afluovide complex is obtained. The light yellow solution shows FIRST OBSERVATION OF AQUEOUS TETRAVALENT an absorption spectrum similar to that previously obtained for solid CmF4I2 (see Fig. 1). CURIUM‘ TABLE I
“Growth hormone-like” activity Total N e t change in dose body weight (mg ) z.1
Sir: We wish to report the first observation of aqueous tettavalent c u r i u m . The measured M+3 = M+4 e- potentials of U, Np, Pu and Am become increasingly negative with atomic n ~ m b e r . ~The . ~ presently unknown value for the Cm+3 = Cm+* e- potential is ex= pected to be more negative than the e- potential of -2.6 to -2.9 volts4and to lie considerably beyond the normal limiting value for stability in aqueous solution. Previous attempts to oxidize C m f 3 in aqueous systems produced no positive results, confirming the expected stability of the 5f7configuration.5-9 It tvas discovered recently that tetravalent ainericiurn (which has only a transient existence in usual
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(1) This work was performed under the auspices of t h e U. S . Atomic I
