Dec., 1958
THERADIATION-INDUCED FORMATION OF AMMONIA
1475
THE RADIATION-INDUCED FORMATION OF AMMONIA‘ BY C. H. CHEEKAND V. J. LINNENBOM U . S. Naval Research Laboratory, Washington, D. C . Received January 2bt 1968
The formation of ammonia in mixtures of nitrogen and hydrogen exposed to cobalt-60 y-radiation has been investigated a t gas pressures up to 100 atmospheres. The ammonia concentration increases linearly with dose, the rat.e depending on the first power of the partial pressure of nitrogen. The rate also depends on the first power of the partial pressure of hydrogen a t low pressures, but becomes independent as the partial pressure of hydrogen is increased. I n a radiation field of 3.4X l o 5 r./hr., a t a nitrogen partial pressure of 34 atmospheres, the rate of ammonia production increases with increasing hydrogen pressure to 1.2 X low5mole/l.-hr. at about 14 atmospheres, and then remainsconstant as the hydrogen pressure is further increased. The rate is also proportional to the dose rate. The reaction is strongly inhibited by oxygen. Added rare gases increase the rate, due to partial utilization of radiant energy primarily absorbed by rare gas atoms. Transfer of excitation energy from rare gases to nitrogen is suggested t o be the principal cause of the increased rate. Addition of Pyrex wool to give a 40-fold increase in surface area does not affect the rate. Radiant energy primarily absorbed by hydrogen does not appear to contribute appreciably to ammonia production. A G-value for ammonia production of 0.7 is estimated for a stoichiometric mixture of nitrogen and hydrogen. passage over anhydrous calcium sulfate to remove moisture. Introduction The reaction vessel and purification system were first evacuEarly work on the synthesis of ammonia by the ated, and then flushed with hydrogen. The reaction irradiation of mixtures of nitrogen and hydrogen vessel again was evacuated and then filled to the desired pressure of hydrogen. With the reaction vessel was confined largely to the effects of a - r a d i a t i ~ n . ~ -partial ~ These early results agreed in general on an ion closed, the purification system was again evacuated and flushed with nitrogen. The desired amount of nitrogen pair yield value M / N of 0.2 to 0.3 (molecules of was then added to the vessel. Argon and helium, when NH3 formed per ion pair produced by the radiation). added, were treated in the same manner. Research grade The equilibrium concentration of ammonia (i.e., krypton and xenon were used without further purification. where the net rate of ammonia formation becomes Pressures below two atmospheres were measured with a manometer. zero, due to the radiation-induced back reaction of mercury In experiments involving krypton or xenon, the inert gas ammonia decomposing into its constituents) was was first added to the reaction vessel, followed by sufficient calculated by Lind and Bardwel12to be 9.1% NHa hydrogen to increase the total pressure by 14.6 atmospheres and nitrogen to increase the total pressure by an additional by volume, and by Ponsaerts3 to be 13.5% “3. 34 atmospheres. Although hydrogen and nitrogen behave An experimental determination of the equilibrium essentially ideally under the conditions of these experiments, composition by d’olieslager and Jungers4 showed their actual partial pressures in the final mixtures exceeded 4.7% NH3. All the experiments cited were per- the pressure increments caused by their addition, due to behavior and consequent reduction of the partial formed a t comparable pressures, slightly below non-ideal of the inert gas with increasing total pressure. The atmospheric. I n a more recent investigation by pressure corrected partial pressures of the components of the mixture Davidge6 on the radiation-induced decomposition were calculated as follows. (a) The number of moles n of krypton or xenon present of ammonia exposed to the mixed neutron-yflux of a reactor, the equilibrium concentration of was calculated from the measured initial pressure P of the gas, the temperature T, the volume V of the container, ammonia was reported to be 60.5% by volume. rare and a compressibility factor K Such a result, if correct, invites a further investin = - PV gation of the effects of radiation on this system. KRT This paper describes an investigation of the yradiation-induced formation of ammonia in mix- Since compressibility data for these two gases were not tures of nitrogen and hydrogen a t gas pressures up available, a generalized compressibility diagram6 was used in order to obtain the compressibility factors. to 100 atmospheres. (b) For gas mixtures of known composition and given temperature and volume, the total pressure can be comExperimental
A 2500-curie Coco source, shielded under 12 ft. of water, was employed for the irradiations. The reaction vessel used for most of the irradiations was a stainless steel cylinder 101/2 in. long, 31/18 in. o.d., with a wall thickness of ‘/32 in. A removable cap was equipped with a Bourdon gauge for pressure measurements and a needle valve for filling. A water-tight housing protected the gauge and needle valve when the reaction vessel was submerged. The reaction vessel could be reproducibly positioned in a cylindrical receptacle surrounded by 10 rod-aha ed Co? sources of approximately 250 curies each. For t i e sake of economy, a reaction vessel of only 35.5-m1. capacity was used in experiments involving the rare gases. Oxygen was removed from the gases a t tank pressure by passage over reduced copper turnings at 550°, followed by (1) Presented in part at the 132nd Meeting of the American Chemical Society, New York, N. Y., September, 1957. (2) 8. C. Lind and D. C. Bardwell, J . A m . Chem. Soc., 10, 745 (1928). (3) E. Ponsaerts, Bull. 8oc. chim. BeEg., 88, 110 (1929). (4) J. F. d’olieslager and J. C. Jungers, (bid.,40, 75 (1931). (5) P. C. Davidge “The Decomposition of Ammonia and Carbon Tetrafluoride by Pile Irradiation,” AERE-C/R-1569, Dec. 21, 1955.
puted by means of Bartlett’s rule,’ P = C N i P i ’ , where P i
is the total pressure, Ni is the mole fraction of constituent i, and Pi’ is the pressure that constituent i would exert as a pure gas if 3,s molar volume were the same as that of the mixture. For each known amount of inert gas, different amounts of hydrogen and nitrogen were assumed, from which a corresponding series of values for total pressure P were calculated. To do this, values of P‘ for the inert gas were again obtained from the generalized pressurecompressibility factor diagram. Nitrogen and hydrogen were treated as ideal; P’ for these gases was then calculated directly from the ideal gas law. The calculated values for P were then plotted as a function of the number of moles of hydrogen and nitrogen. A series of curves resulted, each curve corresponding to a given quantity of rare gas. From these curves the actual amounts of hydrogen and nitrogen present in the experimental mixtures a t a measured total pressure P could then be determined. (6) 0. A. Hougen and K. M. Watson, “Chemical Process Principles Charts,” John Wiley and Sons, Inc., New York, N. Y., 1946, Fig. 103. (7) E. P. Bartlett, H. L. Cupples and T. H. Tremearne, J . A m . Chem. Soc., 10, 1275 (1928).
1476
C.H. CHEEKAND V. J. LINNENBOM 3cK)
- P : I 4 6 ATMOSPHERES HZ
PN;340 765
ATMOSPHERES
x
i o p o EV/LITER-HR
.*
0 X
g
200-
t
A - SURFACE AREA
INCREASED*40-FOLD BY GLASS WOOL
200
100 T I M E (HOURS).
of ammonia concentration with time.
Fig. 1.-Variation
EV/LITER-HR I
2
5
3 4
6
x
io-'O.
9
0
8
7
12 1 3 1 4
II
15 16
Pb= 14.6 ATMOSPHERES
3.4
ax
I
10' r / H R
20
10
0
10
20
15-
30
40
50
€0
70
EV/LITER-HR X I O - 2 0
t -r-742 7 6 5
845
PN*. 3 4 0 ATMOSPHERES 3 . 4 x 105 r f H R
I O
$
EV/LITER-HR X 10-20 391
4 32
B
o P N =~ 13 6 ATMOSPHERES
3 4 I 105 r / n R
I
I IO
Fig. 3.-Dependence
I 20
I
I
I
30 40 50 PHz, ATMOSPHERES,
I 60
of rate of ammonia formation on hydrogen pressure.
(c) From the known number of moles of each constituent resent in the mixture, the corresponding partial pressures Pi' then were calculated according to Bartlett's additive ressure rule. The pressures of krypton and xenon used in 4 are those obtained before the addition of nitrogen and
Kr
.
Since the actual nitrogen partial pressures in the mixtures containing krypton or xenon varied with the amount of rare gas present, due to the compressibility of the latter, the measured rates of ammonia formation in these mixtures were corrected to a constant nitrogen pressure of 34.0 atmospheres. It was assumed that, within the range of pressures used, the experimentally determined linear dependence of the rate on nitrogen pressure and its independence of hydrogen pressure, shown below, held reasonably well in mixtures containing inert gases. The largest correction was made for the mixture containing xenon a t 28.2 atmospheres, in which the corrected rate was 87% of the observed rate. At the highest krypton pressure, the corrected rate was 95% of the observed. No corrections were made for mixtures containing argon or helium, since these gases behaved essentially ideally under the experimental conditions. All irradiations were performed a t approximately 25O, the ambient temperature of the water used for shielding. After irradiation, the gas mixture was bubbled through two water towers in series to absorb the ammonia present. The resulting solution was then treated with Nessler reagent, and analyzed for ammonia spectrophotometrically at 380 mp, using 1-cm. Corex cuvettes. This method is capable of detecting ammonia a t concentrations down to 1 X 10-8 M . Since absorption by pure water was quite efficient, with over 99% of the ammonia being trapped in the first absorber, it was not necessary to add acid to the water to aid in ammonia absorption. The ammonia content of the irradiated gas mixture was computed using the known volumes of water and of the reaction vessel. A correction was made for the incomplete expulsion of the irradiated gas from the reaction vessel into the water towers. A ferrous sulfate dosimeter solution gave average absorbed dose rates of 2.10 X 1P2 and 2.72 X lP2e.v./l.-hr. in the large and small reaction vessels, respectively, based on a G-value of 15.5 ferrous ions oxidized per 100 e.v. absorbed by the solution. The concentration of Fe(II1) was determined optically a t 304 mp wave length, using a Beckman model D U spectrophotometer. The rate of energy absorption in each gas mixture was calculated by multiplying the absorbed dose rate in the dosimeter solution by the ratio between the electron concentrations (number of electrons per unit volume) in the gas mixture and the dosimeter solution. This calculation was based on the assumption that Compton scattering is the predominant mechanism of energy absorption. When the partial pressures of nitrogen and hydrogen were 34.0 and 14.6 atmos heres, respectively, the calculated absorbed dose rate in t\e large vessel was 7.65 X 1020 e.v./l.-hr., or 3 X 106 rods/hr. This corresponded to an average exposure dose rate in the large vessel of 3.39 X 106 r./hr., based on 97.3 ergs absorbed per roentgen per gram of the dosimeter solution.
'Z
Results
886
0
c
Vol. 62
Figure 1 shows that with the partial pressures of nitrogen and hydrogen a t 34 and 14.6 atmospheres,* respectively, the ammonia concentration increases linearly with time. Although ammonia is known to undergo radiation-induced decomposition, the experiments herein reported did not proceed to a sufficient extent for the back reaction to be of significance. The rate of ammonia production computed from the slope of the line is 1.24 X mole/l.-hr. Linear dependence of the rate of ammonia formation on the partial pressure of nitrogen is demonstrated in Fig. 2. Variation of the rate of ammonia production with the partial pressure of hydrogen at two different nitrogen partial pressures is shown in Fig. 3. The rate increases rapidly with increasing hydrogen pressure a t low partial pressures of the gas, but becomes independent as the hydrogen pres(8) This mixture, rather than the stoichiometrio mixture of 3 parts of hydrogen to 1 of nitrogen, was chosen t o increase the stopping power of the gas.
I . .
Dee., 1958
THERADIATION-INDUCED FORMATION OF AMMONIA
sure is raised. The limiting rates for nitrogen pressures of 13.6 and 34.0 atmospheres, respecmole per tively, are 0.47 X lod5and 1.22 X 1.-hour. The effects of adding rare gases are shown in Figs. 4 and 5. The reaction rate in the absence of rare gases is the average of four determinations, in good agreement with results of similar experiments in the large reaction vessel, normalized to the same absorbed dose rate. Figure 4 shows variation in the rate of ammonia formation as a function of partial pressure of the rare gases. The larger effects of the heavier rare gases a t a given pressure are due in part to their greater primary absorption of radiation consequent to their higher electron concentrations. A fairer comparison is obtained by plotting the rate against the concentration of rare-gas electrons, as in Fig. 5. It is to be noted that, at equal rat8es of energy absorption, krypton and xenon enhance the rate of ammonia production to distinctly greater extents than do argon and helium. The dotted line in Fig. 5 shows the expected rate if all the energy primarily absorbed by the rare gases were utilized to produce ammonia a t the G-value of 0.98. The presence of 0.1% oxygen produces a marked inhibition of ammonia production, as shown in Fig. 6. In several experiments, the reaction vessel contained sufficient Pyrex glass wool to give approximately a 40-fold increase in surface area. This appeared to have no appreciable effect on t,he rate of ammonia production. These data, plotted in Fig. 1, fall on the same line as data from the experiments in which no glass wool was present. The slope of the curve in Fig. I, combined with the absorbed dose rate of 7.65 X lozo e.v./l.-hr. gives a calculated G-value for ammonia production of 0.98 molecule NH, formed per 100 e.v. of energy absorbed by the gas mixture. Additional experiments conducted a t a lower absorbed dose rate of 4.71 X lozoe.v./l.-hr. (61.6y0 of the dose rate normally used) resulted in a rate of formation of ammonia equal to 60% of the rate obtained a t the higher dose rate, indicating that the rate of ammonia formation is proportional to the dose rate. The proportionality is also demonstrated by the good agreement between results in the large and small reaction vessels, when normalized to the same dose rate. Discussion The experimental results suggest that the essential radiation effect leading to ammonia formation is the production of one or more highly reactive species of nitrogen. The formation of such species a t a rate proportional to the nitrogen pressure as the rate-determining step for ammonia production would account for the linear dependence on nitrogen pressure. At sufficiently low partial pressures of hydrogen, the rate-determining step would be the reaction between hydrogen and the reactive nitrogen. As the hydrogen pressure is raised, the rate of this reaction approaches the rate of formation of reactive nitrogen as a limiting value. The limiting rates of curves A and B in Fig. 3 are, within ex-
I
2.'
E
w
PN2
*
1477
XENON KRYPTON A ARGON v ARGON (NORMALIZED FROM LOWER OOSE R A T E ) 0 HELIUM 0 0
34.0 A i M O S .
PH- = 14.6 ATt,!OS.
5
c
0
'0
Fig. 4.-Effect
30 40 50 60 70 BO R A R E GAS P R E S S U R E S I N ATMOSPHERES.
20
90
100
of rare gases on rate of ammonia formation. IOzo
8
0
E V I L I T E R - H O U R I N INERT G A S . 16 24
32
,,
, ,
0
ARGON INORMALIZED FROM LOWER OOSE RATE) HELIUM
2
I
0
3
4
I N E R T G A S ELECTRONS PER L I T E R
x
IO-*),
of rare gas electron concentration on ammonia formation.
Fig. 5.-Effect
50-
P = 14 6 ATMOSP!iERES
HZ 0 x
P
40-
L
t
$-
M-
.
20-
T
N;
- 3 4 0 ATMOSPHERES
PO2=4.0
u
10-
0
Cm Hg
/
7.65 x i 0 2 0 EV/L~TER-HR
// /
1
QI
// /
Fig.
perimental error, proportional to the nitrogen pressures. It is to be noted from curve B that a sevenfold increase of hydrogen pressure from about 7 to 50 atmospheres does not appreciably affect the rate of ammonia production. This strongly indicates that radiation-induced ionization and excitation of hydrogen are not of significant importance to the mechanism, and that radiant energy primarily absorbed by hydrogen is not utilized in ammonia formation. The results indicate that, for a given nitrogen pressure, the limiting rate of ammonia production is attained for hydrogen pressures above about 40% of the nitrogen pressure. From the foregoing considerations, it is apparent that the experimental G-value depends on the composition of the gas. mixture. For a given
1478
C. H. CHEEKAND V. J. LINNENBOM
nitrogen pressure the experimental G-value increases with increasing hydrogen pressure up to the limiting rate and decreases as the hydrogen pressure is further increased. For example, when the nitrogen pressure is 13.6 atmospheres, the G-values are 0.91 and 0.66 for hydrogen pressures of 7.8 and 47.6 atmospheres, respectively. However, from data of the curves in Figs. 3A, 3B and 1 are computed, respectively, 1.02, 0.98 and 1.04 molecules of ammonia formed per 100 e.v. of radiant energy primarily absorbed in the nitrogen. On the basis of this reasonably constant value, a G-value of about 0.7 is estimated for a mixture in the stoichiometric ratio of three parts hydrogen to one part nitrogen, since about 70% of the primary absorption is by nitrogen. The influence of rare gases on the reaction rate is not simply attributed to third-body collision processes for several reasons. First, the reaction rate is independent of surface area, which would be expected to influence the rate of a reaction requiring a third body. Second, the relative eficiencies of the rare gas atoms as third bodies cannot be explained easily. Finally, the results in Fig. 3 show that excess hydrogen molecules produce no third-body effects. Increase of the reaction rate by rare gases is therefore attributed to transfer to nitrogen of energy primarily absorbed by rare gas atoms. Argon and helium, having higher ionization potentials than nitrogen, may transfer both ionization energy and excitation energy to nitrogen, whereas krypton and xenon, with lower ionization potentials, may transfer only excitation energy. The observed effects of the rare gases permit some deductions concerning the nature of the reactive nitrogen species. If ionized species are solely responsible for the formation of ammonia, argon and helium would be expected to increase the reaction rate by contributing to nitrogen-ion formation. Krypton and xenon, on the other hand, would be expected to decrease the rate, since transfer of ionization energy would be in the opposite direction, resulting in a removal of nitrogen ions. Figure 5, however, shows that krypton and xenon actually increase the rate to greater extents than do argon and helium for the same energy input. It is concluded, therefore, that the ammoniaproducing species cannot be exclusively ionic, and that excited species must play an important role. This conclusion is further supported by some experiments based on the recent work of Stevenson and Schissler on ion-molecule reactions, 9 They concluded that the reaction A+ Hz --+ AH+ H has a sufficiently large crosssection to occur at every collision. This reaction, which does not lead to ammonia formation, should compete very effectively with transfer of ionization energy from argon to nitrogenlo; hence the transfer of ionization energy to nitrogen should be largely suppressed at the hydrogen pressures used in our experiments. Several experiments at fixed nitrogen and argon pressures of 34 and 27 atmospheres, respectively,
+
(9) D. P. Stevenson and D. 0. Schissler, J. Chem. Phys., (1955). (IO) Suggested by the reviewer of this paper.
+
as, 1353
Vol. 62
gave a slight decrease (about 9%) in the rate of ammonia formation as the hydrogen pressure was increased from 14.6 to 27 atmospheres. These results suggest that either (a) ammonia formation due to transfer of ionization energy from argon t o nitrogen is not completely suppressed by the above reaction at a hydrogen pressure of 14.6 atmospheres, or (b) hydrogen competes with nitrogen for excitation energy of the rare gas. The latter seems more likely, in view of the eEciency of the reaction between A+ and Hz and the relatively high pressure of the hydrogen. It is concluded, therefore, that the positive effect of argon on the rate of ammonia formation is due mainly to transfer of excitation energy. A possible mechanism for this postulated transfer of excitation energy by the rare gases is provided by the work of Groth and Oldenberg11Sl2on the dissociation of nitrogen molecules by excited krypton atoms. The production of nitrogen atoms is reported to be due to transfer of electronic energy of excited krypton into electronic energy of Nz to produce a repulsive level of the nitrogen molecule which dissociates within the first vibration. It should be pointed out that this work does not eliminate the possibility that ionized nitrogen species may still play a part in the formation of ammonia. For example, i t is possible that in a series of consecutive reactions leading to ammonia formation nitrogen ions may act as precursors to excited species, which then react with hydrogen to form ammonia. I n this connection, it is pertinent to point out that Bate@ has suggested that formation of nitrogen atoms by dissociative recombination of Nz+ and electrons is quite efficient. A second possibility is that two independent mechanisms for the reaction may exist, one mechanism involving ionic, the other neutral species; the positive effect on the over-all rate by the rare gases with ionization potentials lower than that of nitrogen might then be explained by assuming an increase in the excitation path large enough to overcompensate for reduction in the ionization path. But this explanation does not seem likely in view of the fact that the rare gases with the higher ionization potentials actually show a lesser effect on the rate; in this case both paths might be expected to be enhanced due to transfer of both ionization and excitation energy to nitrogen. The results of this work would seem to indicate, therefore, that if nitrogen ions enter into the reaction, they do so as precursors to excited ammoniaforming species. Relevant to this question are the results of earlier studies14e15on the rate of ammonia formation in mixtures of nitrogen and hydrogen activated by electron impact. These results seemed to show that ionized nitrogen species are mainly responsible for the reaction, with some evidence that activated hydrogen species also participate, but in a minor role. A similar investigation16 of (11) W. E. Groth, Z . physik. Chem., 1, 300 (1954). (12) W. E.Groth and 0. Oldenberg, J. Chem. Phya., 2.9, 729 (1955). (13) D. R. Bates, Phys. Rev., '78, 492 (1950). (14) A. Caress and E. K. Rideal, Proc. Roy. Sac. (London), A l l t i , 684 (1927). (15) G. F. Brett, ibid., Al29, 319 (1930).
Dec., 1958
ELECTRICAL CONDUCTANCE OF THE LICL-KCL EUTECTIC MELT
the reaction of nitrogen and oxygen under electron impact indicated that this reaction also occurs as a result of the ionization of nitrogen. These coiiclusions were based on the observation that the reactions were negligible at electron energies below the ionization potential of N%,but increased sharply a t energies required to form Nz+ and N+ ions. However, the results do not distinguish whether the ionized species react directly or as precursors t o the product-forming species. Mitral' cites evidence that nitrogen atoms formed in electron bombardment of Nz result oidy from dissociative recombination of NS+ and electrons, and not by direct dissociation of neutral molecules under electron impact. If this is true, the ammoniaproducing species in these electron impact experiments may be electrically neutral, but dependent upon ionization for their occurrence. This would explain the sharp increase in reaction rate when the energies of the bombarding electrons exceeded the ionization potentials of nitrogen. I n a study of the reactions of nitrogen activated by a n electric discharge, Varney'* concluded that the reactive species was electrically neutral, and that, under the conditions of his experiments, nitrogen ions played no direct role in the reactions with either hydrogen or oxygen. His work also indicated that hydrogen activated by an electric discharge does not react with ordinary nitrogen, in agreement with our results. While Varney's experiments do not preclude the participation of ions in the radiation-induced formation of ammonia, they do show that their presence is not necessary, and that ammonia can be formed from neutral reactive species. (16) S. Ya. Pschezhetsky and M. T.Dmitriev, Doklady Akad. Nauk S.S.S.R., 109, 647 (1955). (17) 9. K. Mitra, Phys. Rev., 90, 516 (1953). (18) R. N. Vsrney, J . Chem. Phys.. 29, 866 (1955).
1479
The pronounced inhibiting effect of relatively small amounts of oxygen on ammonia formation is presumably due to preferential reaction between the oxygen and the active nitrogen species to form one or more oxides of nitrogen. When the oxygen has been completely consumed, ammonia formation proceeds a t a rate determined by the nitrogen partial pressure. The G-value of about 0.7 for the stoichiometric. mixture compares favorably with the earlier results obtained by Lind and Bardwel12and by Ponsaerts2 on a-irradiated mixtures. Their reported M / N values of 0.2 to 0.32 correspond to G-values of about 0.57 to 0.91 based on a W value of 35 e.v. absorbed per ion pair formed in the gas mixture. The irradiations reported herein did not proceed far enough t o indicate the composition of the gas mixture a t equilibrium. The longest irradiation period of 233 hours a t the high exposure dose rate of 3.4 X 106 r./hr. (see Fig. 1) resulted in a total energy absorption of only 1.8 X loZae.v./l., forming only 0.0029 mole of NHs per liter of the mixture (approximately 0.14% NHa by volume). Although it would be of interest t o determine the equilibrium concentration experimentally with y-radiation, since the G-values reported here agree well with those obtained from a-irradiated mixtures, it is clear that the low stopping power of the gas mixture for y-radiation, even at high pressures, would necessitate extremely long irradiation periods. Acknowledgments.-The authors wish to express their appreciation to Dr. Howard Etzel and his associates for their cooperation in making available the multi-curie cobalt source used in these irradiations. The technical assistance of E. 0. Davis is gratefully acknowledged.
ELECTRICAL CONDUCTANCE OF THE LiC1-KCl EUTECTIC MELT CONTAINING HALIDES AND ALKALI TITANIUM FLUORIDES AS SOLUTES1)' BY GEORGE J. JANZ,C . T. BROWN,H. J. GARDNER AND C . SOLOMONS Department of Chemistry, Rensselaer Polytechnic Institute, Troy, N . Y . Received April 1 1 , 1968
The electrical conductances over the temperature range 350-400' of the LiC1-KC1 eutectic melt and solutions of NaCl, LiF, NaF KF, LizTiFe, NazTiFo and KzTiFein this melt are reported for the region of dilute concentrations of the solutes. A reduced total specific conductance is found on the addition of fluorides to the chloride eutectic. The decrease in total conductance on the addition of the alkali titanium fluorides to the chloride melt is interpreted in light of the previous cryoscopic results as due to a primary dissociation with the formation of alkali fluoride and TiF,, the latter most probably existing as (TiF4C12)-2 or some similar complex ion.
Introduction The cryoscopic behavior of some alkali halides and alkali titanium fluorides has been discussed in detail in Part I1 of this ~ e r i e s . Interpretation ~ of (1) Part I11 of a series of communications on the Constitution of Chloride Melts Containing Titanium. Part 11: see ref. 3. (2) This work wan supported by the Office of Naval Research, Metallurgy Branch, under Contract Nonr-591(06). (3) G. J. Janz, C. Solomons, H. J. Gardner, J. Goodkin and C. T. Brown, THISJOURNAL, 62, 823 (1958).
the results in the light of the Hoenen theory* and the Temkin model6 for molten salt mixtures suggested that the dissociation of these solute species in this solvent takes place according to the ionization processes MX
=
M+
+ X-
and (4) P. H. J. Hoenen, 2. physik. Chem., 89, 513 (1915). (5) M. Temkin, Acta p h y s . ehem. U. R . S. S., 20, 411 (1945).
(1)
