August, 1939
XOTES
TABLE I THESOLUBILITY A N D HEAT OF SOLUTION OF LANTHANUM NITRATE6-HYDRATE I N ORGANIC SOLVENTS AT 25’ Solvent
Methyl alcohol Ethyl alcohol, 95% Ethyl alcohol, 1 0 0 ~ o %-Propyl alcohol Isopropyl alcohol n-Butyl dcohol Isobutyl alcohol sec-Butyl alcohol t-Butyl alcohol n-Amyl alcohol Isoamyl alcohol t-Amyl alcohol 3-Pentanol n-Hexyl alcohol Cyclo hesanol Benzyl alcohol Allyl alcohol 2-Chloroctlisnc 2,2’-Oxydieth:t1ioi 2-Methouyethanol Glycerol I?-Ethoxyet,hailol Ethylciic glycol Ethyl acet;tte Methyl acctatc Ethyl formate Acetone Cyclohesnnone
Solubility, g. La(NO&.GHzO/ 100 g. soln.
AH, kcal./ mole
87.45 87.47 72.86 73.28 71.89 71.69 45.15 -45.23 42.06 42.53 28,74 28.75 14.98 15.15 13.84 13.65 21.23 21.63 13.52 13.53 11.62 11.89 8.98 9.22 5.68 5.78 16.01 15.88 17.00 lti.97 10.96 11.01 47.01 46.80 40.32 10.40 75.09 74.69 77,03 78.06 81.66 81.45 70.00 70.07 8-1..06 84.07 1.73 1.89 cj2.88 62.85 50.04 50.01 76.64 76. *3 42.84 43.24
-3.75 -3.58 2.58 2.58 1.57 1.64 6.30 6.47 12.0 12.5 8.46 8.34
10.4a 9.24=
1331
Dioxane
73.97 74.13 Acetonitrile 72.45 72.37 o-Toluidine 16.20 16.20 Aniline 15.90 16.05 a Dissolution of solute was slow.
1.66 1.56
The organic solvents containing the hydroxyl group were the best solvents for the salt. As was expected, the solubility decreased as the length of alcohol carbon chain increased. The branching of the alcohol carbon chain had a pronounced effect on the solvent ability; the solubility decreased in the order: normal > is0 > secondary > tertiary. Polyhydroxy1 alcohols were good solvents for the salt since the solubility in glycerol and ethylene glycol was about equal to that of methyl alcohol. Of the non-hydroxy solvents, the ketones and cyclic ethers possessed a high solvent utility for the salt. The low molecular weight esters were better solvents than those of higher molecular weight. The heat of solution could not be measured in a number of the solvents because of the slowness of the dissolution process. The values reported in Table I are those in which dissolution was rapid with the exception of n-hexyl alcohol, cyclohexanone and ethyl formate. The presence of water in ethyl alcohol was readily detected by the AH values. The heat of solutjion became more endothermic, indicating that the A H for the salt may be endothermic in water. With the solubility studies, the presence of 5% of water had little effect on the values obtained. CALCULATED VIBRATIONAL FREQUENCIES FOR HzO1* AND DzO1*
9.85 9.79 14.2 14.4
-3.74 -3.58
-1.78 -1.76
BY GILLIANG O M P E R TAZN~D ~W. J. ORVILLE-THOMASI~ The Ti’eizmann Institute, Rehovoth, Israel Received December 1.2, 1868
The frequency-force constant relatioils for noiilinear XY2 molecules using an incomplete potential function are given in the standard texts.2J Although used implicitly by previous workers (e.g., see ref. 4) the corresponding relations for a complete quadratic potential function do not appear to have been presented. The general quadratic potential function is . ‘ J ‘ = fi(4r12 f ATZ’) fa(r2 4a2) 2f1a (r4a) (Ari
+
+
ATZ)
+ 2flz(AriArd
+
(1)
The Wilson FG-matrix method6 leads to these frequency-force constant relations for the class A, vibrations w1 and w2. ti. 03
5.9s 12.9a 12.00 5.00 4.89 12.4a 16.4~
(1) (a) Dept. of Physics, The University, Birmingham, England. (b) T h e Edward Davies Chemical Laboratories. University College of Wales, Aberystwyth, Wales. (2) G . Herrberg, “Infra-red and R a m a n Spectra,” D. Van Nostrand Co., Inc., London, 1945. (3) T. Y . Wu, “Vibrational Spectra and Structure of Polyatornic Edwards, Molecules,” Brothers, Ann Arbor, Michigan, 1946. (4) S. Smith and J. W.Linnett. Trans. Faraday SOC.,62, 891 (19,515). ( 5 ) E. B. Wilson, J. C. Decius and P. C. Cross, ”Molecular Vibrations,” IUcGtaw-Hill Book Co., Inc., New York, N.Y., 1955.
NOTES
1332 A1
+ hz = + (fl
2/12
sin2P )
-
+ 2/12 cos2 a) + 2ja + cos p + fd - S I P ~ I + 2
(2a)
+ 2/12 sinZP )
(2b)
f i 2 ) (PI 8f1a PZ sin @
A~hp = 2L.f~ ( f l
(/11
[#12
/11/121
and to the following relation for the Class B, vibration, w g A3
=
(f1
- fd ( P I
Vol. 63
observed a term in the rate law inversely proportional to the second power of the hydrogen ion concentration.2 These observations prompted the present investigation designed to determine: (a) whether a species such as may be implied by this type of rate law is formed in detectable quantities in a hydrolytic pre-equilibrium, and (b), the effect on such an equilibrium when deuterium is substituted for hydrogen. The latter information was desired as an aid in the interpretation of the kinetic isotope effects. For comparative purposes the effect of deuterium on the uranium (IV) hydrolysis also has been measured.
where Xi = 4a2c2wi2, mi being a fundamental frequency, p1 = l / m y and p2 = l/mx, P = ,/Z( L YXY) and the force constants are defined in eq. 1. The Fundamental Frequencies of D201sand HzOI8.-As a n example of the use of relations 2 frequency values have been calculated for the Dz0l8and HzO18isotopic modifications of water. The infrared spectra of H20I6and DzO16 have Experimental been studied many times and high-resolution studThe preparation of the neptunium( IV), sodium perchlories have yielded values for the zero-order frequen- ate and deuteroperchloric stock solutions have been yreUranyl perchlorate was prepared by cies and for the anharmonicity constant^.^,^ Smith viously described.3 of uo3 in HClO, or DC104. Uranium(1V) stock and Linnett4 have used these data to determine dissolution solutions were prepared by electrolytic reduction of the values for the four force constants occurring in uranyl perchlorate solutions. Aliquots of the metal ion solutions were added to the eq. 1. These constants used in conjunction with a value of 10-1’31’ for the interbond angle and the appropriate NaC104-HC104 (or DC104)mixtures, in which a ionic strength of 2.0 was maintained, and then appropriate mass factors lead to the values given constant analyzed spectrophotometrically using a Cary Model 14 in Table I for the zero-order frequencies, w, of the recording spectrophotometer. The 6000-7000 A . region was Dz0I8 and Hz018 molecules on substitution in eq. used for the study of the uranium(1V) hydrolysis.4 The 2. 9400-10,000 A. region was used for the neptunium(1V) It seems reasonable to suppose that the anhar- measurements. In this region Np+4 (aq.) has a sharp abmonicity constants will not differ greatly in the sorption band a t 9590 A. which obeys Beer’s law if the Cary spectrophotometer is employed. At this wave length the pairs of molecules H20I6and HzOIs and DzO16and absorption of the hydrolyzed forms of neptunium( IV) is DZO”. only 0.14 that of the unhydrolyzed species. The region scanned permitted monitoring of the solutions t o ensure the The correction for anharmonicity for a fixed force field depends in an inverse fashion on the absence of neptunium(V). The acidity of the solutions were measured with a calomel-glass electrode system using a masses of the molecules as we go from H2016 to vibrating reed electrometer assembly standardized with DzO16. On a simple basis then extrapolated values solutions of known acidity. The measurement and calculacan be calculated for this correction, for the H201stion technique were essentially the same as those described and D2018 species, from the change in mass and by Kraus and Nelson.4 the experimentally determined anharmonicity coResults and Discussion efficient~~.’ for the Hz016 and D2016 molecules. The Hydrolysis of Neptunium(IV).-There is no The frequency values calculated for the observed change in the neptunium(1V) spectrum until the fundamentals, v , are given in Table I. acidity is decreased to approximately 0.1 molar. We wish to thank Professor J. H. Jaff6 for his The existence of N P + ~(aq.) as the predominaat support throughout this work. neptunium(1V) species a t acidities above 0.1 molar has been established previously.6 With furTABLE I VIBRATIONAL FREQUENCIES O F THE WATER MOLECULE ther decrease in acid concentration the height of the 9590 band decreases. Analysis of the data ( I N CM.-’) shows that the simple hydrolytic reaction Exptl. Theor.
A.
Molecule v1
Haole
3651.7 3825.3 1595.0 1653.9 3755.8 3935,6 2
~
~
0
1
26G6 2758.1 1178.7 1210.3 2789 2883.8 2
5
HZ018
Dz018
3647 3804.8 1586 1G35.9 3714 3905.8
2656 2740 1166 1191.3 2762 2851.3
+
N ~ + ~ ( a q . )H,O = NpOH+3(aq.)
+ H30+
(1)
holds for a limited region of acidity in both H20 w1 and DzO solutions. At low acidities polymerizaY2 tion reactions become important as can be inferred W2 from two types of evidence. If the only reacv3 tion of importance was that of reaction 1, a plot of w3 I,”+ or 1 / D + versus total N P ( I V ) / N ~ +should ~ Ref. This paper be linear with a slope of K and no dependence on (0) W. 8. Benedict, N. Ga/lar and E. IC Plyler, J . Chem. P h y s . , 24, the totnl metal ion concentration. Figure 1 is such 1139 (1956). a plot for the D,O solutions and quite clearly de(7) B. T. Darling and Tt. MI.Dennis.on, P h y s . Reu., 57, 128 (1940). lineates the region of acidity at which complex reactions become important. The second type of THE HYDROLYSIS O F NEPTUNIUTV~(IV)~ observation that confirms this interpretation is that the hydrogen ion concentration exhibited a BYJ. C. SULLIVAN AND J. C. HINDMAN slow change with time in those regions where one Argonne National Laboratory. Lemont, Illinois Received December IS, 1968
In a number of kinetic: studies 011 the oxidatiop of neptunium(1V) i n aqueous systems we have (1) Work perfornied under. the auspices of the United States .4,tomic finergy Coniniission.
(2)
J. Q Hindman, J. C. Sullivan and D. Cohen, J A m . Chew
Soc., 7 6 , 3728 (1954). (3) J. C . Sullivan, D Cohen and J C
Hindinan, abzd., 79, 3672
(1957).
K.A. Ilraus and F. Nelson, zbzd., 72, 3901 (1950). ( 5 ) J. C. Sulllvan and J C. Hindman. zbzd., 76, 5931 (1954). (4)
.
