COMMUNICATIOKS TO THE EDITOR
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valent rare earth ion, Ce+, as the solute species,2 and the enormous apparent molar volume of 500 cc. per mole of mobile electrons, in dilute solution.' The recent discovery3 of solid halides of divalent neodymiuin and prasedymium such as SdC12 and PrC12.3supports our own view that cerium enters the solution in molten CeCL as Ce+*, but clarification of the aforenientioned findings appeared desirable. A reinvestigation was started in connection with the general study of molten salt-metal systems a t this laboratory. The nature of our first results is such as t o warrant an early report. In agreement with available thermodj-namjc data n e have found that refractory ovides such as sintered alumina ("Morganite Triangle RR") or sapphire single crystals are not s u i t d for use with even dilute solutions of Ce in molten CeCI3 as they react readily to form cerium oxychloride :tccording to: MZOg 2y13Ce y/3CeC13 = yCeOC1 2.11. For instance, 0.9 g. of cerium metal and 1 G 3 g. of CeC13 prepared by dehydration 111th N&C1 and subsequent qublimation were kept molten under argon a t 850" in a Jlorgaiiite rrucihle for two hours. After leaching with water, 1.62 g. of a n insoluble residue consisting mainly of purplish-white crystal platelets of cerium oxychloride were recovered (X-ray identification). The inner wall of the crucible showed severe attack znd its weight was reduced by 0.25 g., corresponding t o approximately 75% completion of the above reaction. Aluminum metal also was identified. Similar results were obtained x-ith a single crystal of l I g 0 or n slice of high-densi ty T h o 2ceramic 111 a molybdenum crucible. ( A control experiment nitdi such a crucible, without refractory oxides, yielded only traces of CeOC1.) On the basis of these findings it is certain that the data obtained in the e.m f . and conductivity measiiremeiits which had heeii carried oi!t i n Morganite rruciblesl dzcl n o t pcrtazn to thc c'c -CcC13 systpin ! Rather, the added cerium must h:L\ c heen largely, i f not cnmplctcly, cmverted to Ce( C1. Although uIldri' thc circuni+mces any at tempi :it interpretati oii of t h o h e me:i siirciiieiit s In t i 4 he I i d e q u a t e , the o h w , \ et1 tl.m.f.? ni:ij' pcr1iaI)i lie ; i Y ( ~ i l x c l to :L cell
+
trogen is successively titrated with nitric oxide and ethylene in a given system the variable ( H C ~ p r o d n c e d / ? i O d e s t r o y e d ) . x (1 - HCxproduoed/ ?jOdestroyed)-l will be a linear function of the reciprocal of the total pressure. Figure 1 shows that Verbeke and Winkler's data can be correlated in this way. The slope of this correlation is 1.9 i 0.3 mm. (90% confidence limit); the intercept is 0.6 h 0.6.
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1'01. G i
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CH2--CH2 is inherently unstable so that it may be destroyed by other reactions besides the one given above under appropriate experimental conditions. For example, Winkler3 has found recently that with increasing temperature, the HCX vield from the reaction of ethylene and active iiitrogen increases when an unpoisoned vessel is used. This indicated that the wall catalyzed decoriipositioii of CH2-CH, competes with reac-
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~C ~ O ~ C I~cCcij , i (-cc~3 q , (;le
ari:ihic oxygen cwnceiitr:itioii in the fonii of CeOCI. \*e IT 1io:i I i i i h c p i ' o c c ~of clrclopiiig nieiliods of investigating t h c C'c-CeC1 teins 111 such a maiitic'r a'> to void ~ n ~ i ~ i t n bcontniticr le mntcmali. Of ular interest is the question u-hckther the simult:meoiis prehcwcc of the t u o \ . , d r \ i i c t s it:ites of wr111111. Ce+-- and Celt, lend. to < t high electroil mobility. I\ ith T
t ioii five uiitler these conditions. ~ ~ A T E R I A1 L J E ~X I;LOPXfENT L A B O R A ~ O R Y I
