COMMUNICATIONS TO THE EDITOH.
2504
PBXBYB = YBT (2b) where PA and PB are the vapor pressures, to yield
A
where CXAB = in the form
(3)
(YAXB)/(YBXA). This result can be put
(4)
Equation 4 can be solved for A a,nd B using a least squares technique. This is done by assuming successive values for B / A and then solving for the associated least squares value of B in the regression equation
X
Bt (5) where S is the left-hand side of (4), and t is the factor in (4) which multiplies E. The regression results for B and the assumed values of B / A are Ohen plot,ted against. R2, the fraction of explained variance. Where this function is a maximum, the values of B and B I A are "best" in the least squares sense. Alternatively, t'he results can be plotted against the residual sum of squares which passes through a minimum where B and B / A are optimal. Consider the following example taken from Krelschmer, et u Z . , ~ for an ethyl alcohol-isooctane system at =
25". TABLE I (PA/PB = 1.14286) 1 2 3 4
5 6 7 8
XA
YA
aAB
XA/XB
0.0565 ,1182 ,1700 ,2748 ,3773 .5416 .7225 ,8511
0,4441 ,4762 ,4910 ,5073 ,5153 ,5285 .5501 ,5994
0,0749 ,1473 .2132 ,3688 .5699 1.0535 2.1356 3.8232
0.0598 ,1338 ,2048 ,3793 ,6051 1.1834 2.6101 5,7114
From plots of the data in Table 11,the optimum value of B / A was found to be 0.675 from which was found TABLE I1 1,EAST S Q U d R E S S O L U T I O X FOR THE \'AS
1 2 3 4
5 6 7 8 9
LAARCONST.4NTS
B,
€314 assumed
calcd.
R=
0.2 .3 .4 .5 .6 .7 .8 .9 1.0
0.4030 ,4941 ,5787 ,6575 ,7315 ,8018 ,8689 .9336 ,9962
0.8759 ,9368 ,9687 .9847 ,9916 ,9928 ,9904 ,9857 ,9797
(1) C. E. Krelschmer, J. h-owakowska, and R. Kiebe, J. Am. Chem. Soc.9 70, 1786 (1948).
Vol. 67
B = 1.600 and B = 0.640. The above calculations mere carried out on an IBM 7090 regression program. PRODUCTS RESEARCH DIVISION LEOXMIR Esso RESEARCH ASD ENGINEERING COMPANY LINDEN,NEWJERSEY FRANK E. STEIDLER RECEIVED AUGUST12, 1963
THERMAL FORMATION OF FERRITES FROM AMORPHOUS PRECIPITATES
Sir: It is well known that spinel type ferrites are produced from mixtures of oxides, hydroxides, or salts of Fe3+ and a variety of bivalent metals in the desired proportions. The reaction may be carried out by heating the dry mixture for some hours a t a temperature around 1000". Alternatively, the desired metals may be coprecipitated as oxides, hydroxides, or carbonates which are then converted to a ferrite structure by heating. This conversion may be preceded by a drying operation or may be carried out by heating the precipitate in the reaction liquid. This last method is described in a paper by Sato, Sugihara, and Sait0.l The present communication is concerned with related work carried out in 1959 in the A.E.I. Research Laboratory, Harlow.2 A solution of metal sulfates in the ratios to yield Ki,$Zno$Fe2O4was allowed to react a t 60" with the stoichiometric equivalent of sodium carbonate solution containing a smaller proportion of sodium hydroxide (to ensure complete precipitation of the zinc and nickel). After reaction, a bulky flocculent precipitate was obtained; in numerous repetitions of the experiment the pH of the liquid after reaction mas 9.0 or slightly higher. Carbon dioxide was evolved on boiling, but it is not expected that this had a large effect on the pH. In this present work, spinel formation was judged by increase in density and development of ferrimagnetism; X-ray diffraction was not applied. It was found that heating in the reaction liquid for 30 min. a t 100' caused dehydration of the gelatinous precipitate ; this became darker in color, assumed a fine powdery texture, increased greatly in apparent density, and developed noticeable ferrimagnetism. Higher temperatures (using an autoclave) up to 210' increased the effect, so that after 30 min. at 210' the material began to resemble powder mechanically mixed and reacted TABLEI Temp. of treatment, ' C .
Degree of magnetism, g. Heated Heated in after aashreaction ing and solution drying
Apparent density, g oc. Heated Heated after in washing reaction and solution drying
100 0 04 Xi1 3 17 120 0 11 Nl1 136 0 57 Xi1 150 2 34" Nil 3 82 210 3 41 Si1 4 18 400 0 05 500 1 56 600 1 90 900 2 68 a The corresponding value when this material 0.5 hr a t 150" in water m:ts 0 98.
-
2 92
__
3.18 3 40 4 35 4.52 5 05-5 10 was heated for
(1) C . Sato, M Sugihara, and NI. Saito, J. Chem. Soc Japan, I n d Chem. Sect., 68, 52 (1962). (2) F, G ,Stickland. British Patent 914,773 (1960).
Nov., 1963
CORIJIUSICATIONS TO THE EDITOR
2505
measurements on the systems AgK03-KK03 and molten metal oxides-SiOz,sand liquid junction potential measurements on the system AgN03-CsN08, show the great dependence of the ionic mobilities on the composition and temperature of the system. Equalization of the mobilities of like charge ions in ionic melts, while occurring in many systems, is not a general phenomenon as stated by Laity and Moynihan.10 They report that data for a t least ten different systems are consistent with t’hehypothesis that the mobilities of like-charged ions in fused salt mixtures are equal within about 10 to 15% a t all concentrations.ll Many of the systems discussed by Laity and Moy:nihanlo were studied. by measurement of the liquid junction potential. No conclusion regarding the relative mobilities of cations can be drawn from zero values of the liquid junction. potentials15 as was done by MurgulCHEMISTRY AKD MATERIALS SECTION F. G. STICKLAXD escu and Marchidan,l6 since the assumption of constant AEI RESEARCH LABORATORY mobilities over the concentration range of the cell TEMPLE FIELDS, HARLOW necessary for integrating the equation relating transESSEX,ETGL’4ivD port numbers and liquid junction potentials is not RECEIVED AUGUST 15, 1963 valid, as can be wen from mobility measurements on the systems AgNO8-Kn’OJ and NaN03-Kn’03.14 The observation of anionic migration for traces of certain metals strongly suggests that such ions form DIFFEREKCES I K THE MOBILITIES O F “complexes” in the melts. These “complexes,” being LIKE CHARGE I O N 3 IK MOLTEK SYSTEMS equilibrium phenomena, will depend on the composition Sir: and temperature of the system. For binary mixtures, We wish to report on some preliminary results, having one ion in common and of approximately equal which me have obtained on ionic mobilities of cationic molar composition, the relative mobility of two ionic traces in alkaline earth halide melts and in the eutectics species depends on the state of aggregation14 of the NaK03-KN03 and KaNOz-KX03-LiN03. system. As the temperature increases, the aggregates During the course of counter-current electromigration disappear, and the ions can compete for other species in experiments similar to the ones described previously,’ the nielt to form ‘Lcomplexes”which will determine the it was found that in SrBrz a t 770-800O the cationic migration velocity. Lantelme and Chemla have shown migration of the specie containing the strontium ion was how the variations in the self-diffusion coefficients aiid appreciably fa,ster than that containing calcium or magionic mobilities for the system NaNOrKN03 are nesium ions, while the specie containing barium migrated consistent with this explanation. The apparent actifaster in relation to strontium. I n CaBrz at the same vation energy for ionic mobility therefore will depend temperature, the species containing strontium and strongly on the state in which a given specie is to be barium migrated faster, and the ones containing found and, while it is possible that the ionic mobilities magnesium migrated slower than calcium. These become the same a t a given composition for one temphenomena were found to hold for concentrations of perature, they are most likely not to be the same a t traces of about 100 p.p.m. Direct measurements of another temperature due to differences in the activation these mobilities are made a t present on films of alumina energies. powder.2 We also wish to point’out that the observed mobilities Ionic mobility measurements of cationic traces in of alkaline earth ions in solution in an alkaline earth nitrate eutectics have been made on films of alumina bromide (Ca, Sr) art 770-800° and in SaSOz-KNOBa t powder under a flow of dry Nz and the results are re270’ increase linearly as a function of their simple ported in Table I.3 These and other systems are being ionic radius, while the observed mobilities of the alkali further investigated with relation to temperature, com(7) E‘. R. Duke and B. Owens, J . Electrochem. Soc., 105, 476 (1958). position, and effect of the supporting media on the mi(8) V. I. Malkin, S.F. Khokhlov, and L. A. Shvartsman, Intern. J . A p p l . gration. Rad. Isotopes, 2, 19 (1957): 1’. I. Malkin, Zh. Fiz. Khim., 35, 336 (1961). These preliminary results, together with previous (9) J Ketelaar and A. Dammers de Klerk, paper no. 88 presented a t the 13th C.I.T.C.E. Meeting, Rome, 1962. literature data on counter-current electromigration ex(10) R. W.Laity and C . T. Moynihan, ,J. Phys. Chem., 67, 723 (1963). periments in the systems SrBrz-BaBrz, CaBrz-KBr, and (11) In addition to the systems discussed by Laity and Moynihan, equalization of the ionic mobilities occurs also a t certain compositions and CaBr-LiBr, electrophoresis and electromigration extemperatures for the systems LiKOa-NaNOa, LiNOa-KNOa,’? LiBr-NaT%r, 6 periments of alkali and alkaline earth ions in LiBr-KBr,‘X and NaNOrKNOa.14 of metal ionic traces in KC1-LiC1,6 transport number (12) F. Lantelme and X. Chemla, J . chim. phys., 60, 250 (1963).
dry a t much higher temperatures. Very considerable dilution of the reaction solution before the heat treatment had only limited effect on the transformation. Table I gives some idea of the results obtained: the degree of magnetism was assessed empirically by measuring the force required to separate a standard magnet from a small receptacle filled with ferrite. Similar results were obtained from electrolytically produced mixed hydroxides. It has since been shown that the transformation to a spinel with magnetic properties can be carried out under the described conditions with wet precipitates yielding lFeFezO4, Xo.~Zno.4FeaO~, and Kio.45Zno.45M~.lFe~04. This work agrees with the comparable work of the Japanese scientists, but goes beyond it in its description of the much more poverful effects to be obtained by use of higher temperatures in an autoclave.
(1) F. Mdnes, G. Dman, and E. Roth, J . chzm. phys., 60, 245 (1963). (2) S.Forcheri and C. Monfrini, J . Phys. Chem , 67, 1566 (1963). (3) R. A. Bailey and A. Steger, J . Chromatog., :11, 122 (1963). (4) H. J. Arnikar, Compt. rend., 244, 2241 (1957). (5) H. J. Arnikar, Ann. p h y s . (Paris), 4, 1291 (1959). (6) G. Alberti, G. Grassini, and R. Trucco, J. Blectroanal. Chem., 3, 283
(1962)
(13) J. Perie, M. Chem!.a, and M. Gignoux, Bull. soc. chim. France, 1249 (1961). (14) F. Lantelme and M. Chemla, Bull. soe. chim. France, 2202 (1963). (15) R. W. Laity, J . Am. Chem. Soe., 79, 1849 (1957); R. W. Laity, in “Reference Electrodes: Theory and Practice,” ed. by D. J. G. Ives and G. J. Janz, Academic Presn, Xew York, N.Y., 1961, pp. 548 ff. (16) I. G. Murgulesou and D. I. Marchidan, Zh. Fiz. Khim., 34, 2534
(1960).
