Robert A. Penneman

Infrared Absorption Spectra of Aqueous HF2—, DF2—, and HF

Strong infrared absorption bands of KHF2 appear at 1233 cm—1 and 1473 cm—1 in the solid, and are observed at 1206 cm—1 and 1536 cm—1 respectively, in H2O solution. Corresponding values for KDF2 are 888 cm—1 and 1045 cm—1 in the solid, and 873 cm—1 and 1102 cm—1 in D2O solution. In saturated KHF2 and in KHF2 solutions containing excess HF, there appear new, broad absorption bands attributed to polymeric species, e.g., H2F3—. The HF2— ion is observed in concentrated aqueous HF; in addition, there is a strong absorption at 1820 cm—1 which is not shifted in D2O‐HF mixtures.

Infrared Spectra and Structure of Uranyl and Transuranium (V) and (VI) Ions in Aqueous Perchloric Acid Solution

Infrared spectra of aqueous solutions of U(VI), Np(VI), Pu(VI), and Am(VI) show conclusively that these ions exist as symmetrical and linear, or nearly linear, XO2++. The spectra of Np(V) and Am(V) show that they are probably XO2+ ions. Force constants and estimated distances are given for the X—O bonds. For the XO2++ series, the X—O force constant is expressed as a parabolic function of atomic number, with the maximum occurring at NpO2++. This is contrary to behavior expected if there were a regular contraction in ionic radii for the series XO2++.

Infrared Absorption Studies of Aqueous Complex Ions. II. Cyanide Complexes of Cu (I) in Aqueous Solution

In the system CuCN–KCN–H2O, we have observed infrared absorption spectra of three distinct complex ions: Cu(CN)2−,e=165±25 mole−1 liter cm−1 at 2125 cm−1;Cu(CN)3=,e=1090±10 mole−1 liter cm−1 at 2094 cm−1;andCu(CN)4≡,e=1657±15 mole−1 liter cm−1 at 2076 cm−1. At 29°C, the constants for the dissociation of Cu(CN)4≡ into Cu(CN)3=+CN— are: K4, 3c = 0.0076±0.0005 mole liter—1 [in terms of concentrations at 0.1—0.2f Cu(I)] and K4, 3a = 0.026 mole liter—1 (in terms of activities). Analogous values for the dissociation of Cu(CN)3= into Cu(CN)2—+CN— are K3, 2c = (2.44±0.36)×10—5 mole liter—1, and K3, 2a = 4.2×10—5. The above values are calculated from approximately 100 determinations. At 25°C, the corresponding values of these constants are approximately K4, 3c = 0.0057 and K3, 2c = 1.5×10—5.Using the activity constants determined in this paper and a value of 1×10—24 for the constant: [Cu+][CN—]2/[Cu(CN)2—] we derive the following values: [Cu+][CN—]3/[Cu(CN)3=] = 2.6×10—29 and [Cu+][CN—]4/[Cu(CN)4≡] = 5×10—31. The ...

Infrared Absorption Studies of Aqueous Complex Ions: I. Cyanide Complexes of Ag(I) and Au(I) in Aqueous Solution and Adsorbed on Anion Resin

Techniques are described for obtaining infrared absorption spectra of complex cyanide anions in aqueous solution and adsorbed on anion resin. In the system AuCN–KCN–H2O, only the soluble complex ion Au(CN)2— is observed; the molar extinction coefficient (e) is 477±25 mole—1 liter cm—1 at 2147±1 cm—1. When Au(CN)2— is adsorbed to the extent of 47 weight percent on Dowex‐A‐1 resin, its absorption maximum appears at 2138 cm—1. Three distinct silver cyanide complex ions were observed in aqueous solution: Ag(CN)2—, e=264±12 at 2135±1 cm—1; Ag(CN)3—2, e=397±23 at 2105±1 cm—1; Ag(CN)4—3, e=556±83 at 2092±1 cm—1. Approximate values (calculated in terms of activities) of the dissociation constants for the tri‐ and tetra‐cyanide complexes into the next lower complex are K3, 2=0.20±0.05 mole liter—1, and K4, 3=13,4±4 mole liter—1, respectively. Over ranges of silver concentrations from 0.1—1.0 formal and of free CN— ion concentrations from 0.05—1.5 molar, the concentrations of Ag(CN)2—, Ag(CN)3—2 and Ag(CN)4—3 can b...

THE RADIOCHEMISTRY OF AMERICIUM AND CURIUM

A review of the nuclear and chemical features of particular interest to the radiochemist, a discussion of problems of dissolution of a sample and counting techniques, and a collection of radiochemical procedures for the elements as found in the literature are given. (W.L.H.)

Application of bond length-strength analysis to 5f element fluorides

Abstract The considerable body of single-crystal data available on 5f element fluoride structures is analyzed using Zachariasens formulae for bond lengths and bond strengths. The utility of the approach is demonstrated. Some reassignments are suggested by the analyses.

The Solution Absorption Spectra of Americium(III), (V), and (VI)

Detailed absorption spectra of Am(III), (V), (VI), and Eu(III) in perchloric acid were obtained over the range 200–800 mμ using the Cary Recording Spectrophotometer. Molecular extinction coefficients obtained from the average of several determinations are given for each absorption peak of the americium species. No vibrational fine structure similar to that reported for U(VI), Np(V), Np(VI), and Pu(VI) was found in the visible and ultraviolet spectra of Am(V) and (VI). This fine structure has been interpreted as arising from symmetrical metal‐oxygen vibration in ions of the type MO2+ and MO2++.

Electronic Spectra of Cesium Fluoride Complexes of Pentavalent Neptunium

The absorption spectra of magenta‐colored CsNpF6 both as a mull of the crystalline solid and as a solution in CsF·2HF were obtained under various conditions. The room‐temperature spectra were unique to the electronic energy levels of the seven Russell–Saunders states for the 5f2 configuration, split by spin–orbit coupling into 13 free‐ion levels; this confirms the chemical evidence for the presence of pentavalent neptunium. At liquid‐nitrogen temperatures the spectra of CsNpF6 mulls were interpreted in terms of the free‐ion f–f transitions of Np5+ split by an Oh crystal field. Term assignments to the following experimental energy levels obtained at room temperature were made on the basis of the observed Stark splitting in the low‐temperature spectra, and agreement with calculated energy levels (in cm−1): 3F2 = 4337, 3H5 = 8425, 3F3 = 8797, 3F4 = 9701, 3H6 = 13 738, 3P0 = 16 129, 1D2 = 16 736, 1G4 = 18 265, 3P1 = 19 531, 1I6 = 20 619, 3P2 = 26 667. All levels above the 3H4 ground state were observed except...

Stabilization of actinides and lanthanides in high oxidation states

Abstract The stabilization of actinides and lanthanides in unusually high oxidation states can be rationalized on the basis of the interplay of crystal-lattice, acid-base, charge, size and redox factors. In this paper we apply arguments based on such influences to selected high-valent actinide and/or lanthanide compounds. Two new structural studies of the incorporation of f-element cations into the important perovskite structure are briefly discussed. Recently developed superoxidizer-superacid techniques which hold great promise for synthesis of new high-valent f-element fluorides are also mentioned.

The absorption spectrum of potassium hexafluoronickelate(IV): Electronic spectra

Abstract Compounds of the formula M2NiF6 containing tetravalent nickel and the three heavy alkali metals were prepared and their electronic spectra studied. The observed peaks were assigned to the crystal-field energy levels for an octahedral low-spin d6 configuration. The crystal-field parameters for K2NiF6 are Dq = 2090 cm−1 and B = 485 cm−1. The fine structure components appearing on the 1 A 1v → 1 T 1 transition have been correlated with data for the ground state vibrational frequencies, and the occurrence of a Jahn-Teller distortion is postulated for this level.