CYANIDE-1, 10-PHENANTHROLINE COMPLEXES OF Fe(I1)
Oct. 20, 1957
proposed t o explain the weight loss anomalies encountered in the reaction of UF4with dry oxygen. The extent t o which this side reaction occurs during a UF4 oxidation may be obtained from chemical analyses and weight losses. Since UOZF? was found t o be quite stable a t the temperatures of interest, it was used as a measure of the UFa consumed by the reaction 2UF4 0 2 + UO?Fe 4- UFa. However, more UFa was consumed during an experiment than could be accounted for by U02F2 formation. Hence, the amount of UF4 involved in the side reaction was obtained by difference. Table I11 contains data for oxidations a t various temperatures calculated on this basis. As seen from these data a considerable fraction of UF4 is consumed by the side reaction. The scatter a t each temperature is perhaps due to differences in packing of the individual powdered UF4 samples. TABLE I11 EFFECTOF THE SIDEREACTIONUF4 UFa +- 2UFs AT VARIOUSTEMPERATURES
+
542 1
The observed stoichiometry lies somewhere between the case of no side reaction (eq. 1) and that of a complete back reaction with UFe (eq. 2). I t is also seen from Fig. 3 that UFs is expected t o be relatively unstable in the region of 600". Its disproportionation has been reported previously.11 This property of UFb can help explain the observed deposits of uranium compounds inside a reaction vessel. UFa formed a t high temperature by the postulated side reaction apparently decomposes a t a fairly rapid rate as it is being swept out of the reaction vessel. UFa is deposited initially by this mechanism. However, a t temperatures greater than 600°, UFa may be reoxidized3 to U02F2. Use of a thermocouple probe indicated that little U02F2was deposited in regions where the temperature was lower than 600".
+
Temp. Run 1
2 3 4 5 6
7 8 9 10 11 12 13 14 15 16 17 18 19
("e.) 900 800 800 800 800 800 800 800
750 750 700 700 700 700 G5O 600 600 600
600
UF,
pro-
duced
UF4 consumed by reaction with Oz
Total UFI consumed
(g.)
(g.1
(g.)
(g.)
U0zFz
Initial 12,1122 6.4019 12.5406 11.0964 12.3706 18.4868 9,8120 17.2728 9.8170 5.9361 4.1478 14.4736 11.9810 5.9359 5.9325 12.9860 8.6912 10.0843 10.9064
4 . 1 4 9 1 8 , 4 3 1 0 10,8205 0.8789 1.7859 2.1064 3.0497 6.1970 8.8085 3.5233 7 . 1 5 9 3 9.4626 1.8925 3 . 8 4 5 6 7.8283 5.1336 10,4315 15.3103 5.6796 7.7115 2 7951 2,0876 4.2420 6.4917 2.8849 5.8621 7 . 8 4 0 2 0,1186 0 , 2 4 1 0 0.3582 0.3303 0.6712 0 7009 4.5541 9 , 2 5 3 9 9.9503 2 . 9 1 1 6 5.9164 8.3630 0,3701 0 , 7 5 2 0 0,9977 ,0142 0,0288 0.0924 ,6108 1.2411 1.7171 ,1089 0.2213 0,3297 0,2264 0,7544 ,1114 ,3773 0 . 7 6 6 7 1.6500
UF4 consumed by side reaction Grams 70 2.3895 2 2 . 1 0.3205 15.2 2.6115 2 9 . 6 2.3033 2 4 . 3 3.9827 5 0 . 9 4.8788 3 1 . 9 2.0319 2 6 . 3 2.2497 3 4 . 6 1.9781 2 5 . 2 0,1172 3 2 . 7 ,0297 4.2 ,6964 7.0 2.4466 2 9 . 2 0,2457 2 4 . 0 ,0636 6 8 . 8 ,4760 2 7 . 7 ,1084 3 2 . 9 ,5280 7 0 . 0 .7833 5 0 . 5
Material balances show that neither of the following reactions accurately describes the consumption of the UF4. 2UF4 0 2 +UO2F2 4- UFa (1) 3UF4 f 0 2 +2UFs f UOzF2 (21
+
[CONTRIBUTION FROM
THE
-. .
,-n
L
~~i
Z X
fI.%TED
Constant
Kl K2
a'
At I O o
x cx 4 x
(i
Ti,
io-c
10-~ 10-11
(5) '1'. s I.W. I 70. :! : I S ( I ' l 4 Y l
Approximated values A t 25'
1 x 10-5 1 x 10-6 1 . 4 x 10-:0
1
1 . .
A-8
I\.
EQEILIBRILZd C U X S T A X T S
.
.
.-I
;,
x
.x
10-22 10-27
hr. K ~ ~ I I C ~ I. ~T W I r i
I.. I
At 40"
2 X l(J-5 2 x l(J-2 4 . 1 x lo-'" 1 ,
,
..... . ..
W I ~ > ~ ~ > ?'I: ,1115
/tIiin'.
\I
FLUORIMETRIC STUDY OF
Oct. 20, 1957
Insofar as this is true, the mechanism of the disproportionation reaction does not appear t o involve either 1,lO-phenanthroline or the cyanide ion. Attempts t o measure the equilibrium constants for reactions 1, 2 and 4 directly were unsuccessful. I n view of the experimental difficulties involved in the study of these equilibria i t seems justifiable t o make use of an approximation to a t least obtain the order of magnitude of their equilibrium constants. The approximation is based on the assumption that the FePh3++ and FePh(CN)d- ions
THE
THORIUM-MORIN SYSTEM
5425
are the predominating ionic species produced when pure water is saturated with respect to FePh,(CN)Z. I n this event their concentrations are approximately equal because of electrical neutrality considerations, and K1 and K z are approximately equal. Values for the various constants approximated in this manner are presented in Table IV. The possible analytical applications of the reactions revealed by this investigation are receiving further attention and will be described a t an early date. ANN ARBOR,MICHIGAN
u. s. GEOLOGICAL SURVEY] A Fluorimetric Study of the Thorium-Morin System [COSTRIBUTIONFROM
BY ROBERTG. MILKEYAND MARYH. FLETCHER RECEIVED MAY23, 1957 Thorium reacts with morin to yield a yellow complex that fluoresces when irradiated with ultraviolet light. The effect on the fluorescence of such variables as concentration of acid, alcohol, thorium, morin, and complex; time, temperature and wave length of exciting light are studied to determine experimental conditions yielding maximum fluorescence. The effects of Zr+', Alfa, Fe+3, Ca+* and La+3 are discussed. The fundamental relationships between light absorption and fluorescence are expressed in a general equation that applies to a three-component system when the fluorescence is measured in a transmission-type fluorimeter. This general equation is used to obtain an expression for the fluorescence of the thoriummorin system. Equations, derived from experimental data, relate both the fraction of thorium reacted to form complex and the fraction of unquenched fluorescence to the concentration of uncombined morin. These functions, when combined with the general equation, give an expression which relates the total net fluorescence to the amount of uncombined morin in the solution. This last equation can be used to determine the one region for the concentration of uncombined morin that gives maximum sensitivity for the system. Calculated standard curves are in good agreement with experimental curves.
Introduction Morin reacts with thorium in weakly acid solut i o n ~ ' -to ~ form a stable yellow complex that fluoresces yellow-green when its solutions are irradiated with ultraviolet light. Both the color and fluorescence of this complex have been investigated. The results of the spectrophotometric study have been presented in an earlier paper6 which evaluates the color system as a basis for the quantitative determination of trace amounts of thorium. This paper evaluates the fluorescent system as a basis for the quantitative determination of trace amounts of thorium. Some of the theoretical and mathematical relationships between fluorescence and light absorption, as exhibited in the thoriummorin system, are also included. This report is part of a program conducted by the U. S. Geological Survey on behalf of the Division of Raw Materials of the U. S. Atomic Energy Commission. Characteristics of Thorium-Morin System The reaction between thorium and morin occurs in slightly acid solution according t o the equation ThXr
+ 2M.H
ThMQXz
+ 2HX
(1)
where M - H is morin (5,7,2',4'-flavanol) having the structure OH
HO \()'-=-OH W O OH 0
\
H
(1) H.GBto, J . Chem. SOC.J a p a n , 69, 625 (1933). ( 2 ) H.GBto, Tohoku Imp. Uniu. Sci. Rcpls., 1st ser., 287 (19401941). (3) H. H. Willard and C . A. Horton, Anal. Chcm., 2 2 , 1190 (1950). (4) H. H. Willard and C. A. Horton. i b i d . , 22, 1194 (1950). ( 5 ) AT. 11. Fletrhpr anti K. C , . Milkey, i b i d . , 28, 1-102 (1956).
and X is a univalent negative ion such as Cl- or NO3-. The reaction is instantaneous and results in the formation of a single, yellow, stable complex having a molar ratio of T h :M of 1:2. The equilibrium constant for the reaction, according to the equation
is approximately 1 X IO6 ( 5 ) . Solutions of the complex fluoresce a bright green when irradiated with long wave length ultraviolet The wave length band of the fluorescent light ranges from approximately 488 t o 555 mp, with peak intensity between 513 and 533 mp, as determined by visual inspection with a spectroscope (personal communication, H. Jaffe, U. S. Geological Survey, and C. E. White, Univ. of Maryland, 1952). Absorption spectra for solutions of the complex (curve B) and for pure morin (curve A) are presented in Fig. 1. The region between the dotted lines in this figure indicates the wave length band of the fluorescent light. The fluorescence occurs in that part of the spectrum in which light is transmitted virtually completely by both the complex and morin. Moreover, solutions with thorium concentrations as large as 50 mg. of T h o , per 50 ml. also completely transmit all light in this spectral region. The spectra indicate that light having a wave length near 410 mp would be advantageous for the production of fluorescence, and such light (404.7 mp) was used to establish the experimental conditions. Experimental Data Apparatus and Reagents. Transmission Fluorimeter.-The transmission fluorimeter, especially h i l t for this study, is zrratigcd so illat t h e light sotirce, s x t ~ ~ p (:ell l r wid p11uti+
