Aug. 20, 1057
PREPARATION AND PROPERTIES OF
RHENIUM OXYCHLORIDE
4257
The derived value is in excellent agreement with be desirable not only to repeat the analyses of perthe figure 107.880 which has been accepted for fluorobutyryl chloride and undertake the analyses many years by chemists. Although this outcome of a pure sample of the corresponding bromide, but is just another way of showing that the results of it would be important to explore the suitability of our present series of analyses are consistent with the acid halides of other perfluoroaliphatic acids the physical values for the atomic weights of fluo- for comparing the atomic weights of fluorine and silrine and carbon, i t is of particular importance be- ver. In the latest “Report on -Itomic %‘eights” cause of the special position of the atomic weight of silver as the practical basis of the chemical atomic LVicherslypresents a most ealightening discussion weight scale. The significance of this last point of the “Problem of Two Scales” and raises the will be elaborated further in the section which fol- question of unifying the chemical and physical atomic weight scales. Of the various possibilities lows. The possibility of comparing fluorine and silver Wichers regards a common scale, based on fluorine by the analysis of perfluorobutyryl chloride opens with an assigned mass of 19, as the most attractive the way for a consideration of a number of questions. one. The fact that our work gives a comparison For one thing serious consideration can now be between the atomic weights of fluorine and silver given to the adoption of fluorine as the basis of the (the practical basis of many chemical atomic chemical atomic weight scale. Some of the argu- weight values) lends support to X-icher’s concluments in favor of the change may be noted here: sion. The element is anisotopic22and hence, unlike oxyAcknowledgments.-This work on atomic weight gen, its chemical atomic weight is constant. Fur- of fluorine has received partial support from several ther to go from natural oxygen (16) to an assigned grants to the senior author. Small grants from the value of 19 for fluorine would mean an increase in Cyrus A I . Vi‘arren Fund and the Permanent Science the chemical atomic weight values of the other ele- Fund of the American Academy of Arts and ments by less than 1 part in 20,000, a very minor Sciences in 1937-38 were of great help; in fact a change which should not present serious practical Troemner No. 10 balance, purchased a t that time, problems. Finally, since the atomic mass of was used in the present series of experiments. fluorine can be established quite accurately on the All the work on derivatives of trifluoroacetic acid physical scale by physical methods, fluorine could carried out immediately following the war was serve as a bridge between the two scales. Natu- supported by funds from an ONR Contract (onr rally, if fluorine were to be accepted as the basis of #71600). A contract with the Division of Research, the chemical scale there would be need of further A.E.C., and a grant from the National Science work to establish as accurately as possible the re- Foundation, both primarily in support of other lationship between fluorine and silver. It would atomic weight projects, provided invaluable assistance a t critical points in the present set of experi( 2 2 ) T h i s t e r m h a s been proposed by H. E. Duckworth (private communication) as more correct etymologically t h a n t h e older t e r m s ments. The senior author acknowledges gratefully “monoisotopic” a n d “simple” t o describe a n element havina only one all of this financial assistance. atomic species. For further discussion of term “anisotopic,” see PORTLASD,
f o o t n o t e 46. ref. 19.
[COYTRIBETION FROM THE
OREGOS
RICHARD BESBRIDGE IYETHERILL LABORATORY OF CHEMISTRY,
PURDUE UNIVERSITY]
The Preparation and Properties of Rhenium Oxychloride (Re0,Cl) BY CLARENCE J. WOLF,^ A. F. CLIFFORDAND W. H. JOHNSTON RECEIVED APRIL 15, 1957 Rhenium oxychloride has been prepared in good yields b y direct chlorination of rhenium trioxide. T h e gaseous infrared spectrum, the gas density and t h e vapor pressure were determined a t ronm temperature. T h e general handling procedure and some properties of this compound are discussed.
Introduction Rhenium oxychloride has been prepared by several investigators. 3-7 All of these preparations (1) T h i s work was supported in p a r t b y t h e United S t a t e s Atomic Energy Commission under C o n t r a c t No. At(ll-1)-166 with P u r d u e University ( 2 ) T a k e n in p a r t from research work done b y Clarence J. Wolf for a thesis to b e submitted to t h e G r a d u a t e School of P u r d u e University in partial fulfillment of t h e requirements f o r t h e degree of Doctor of Philosophy. (3) A. Bruke and K. Zielget, Be?., 66, 916 (1932). (4) H. V. A. Brisco, P. L . Robinson a n d A. J. Rudge, J . Ciiem. Soc., 2643 (1931). ( 5 ) W. G e J m a n n a n d F r . W. Wrigge, Z. a n o y g . allge?n. Chpm., 214, 248 (1933). (6) 0. W. Kollipg, Trans. Kansas A c a d . Sci., 66, 378 (1953). (7) Rhenium tetrachloride is a mixture of t h e trichloride and t h e pentachloride.
use essentially one of two procedures, either the reaction between rhenium(VI1) oxide and rhenium tetrachloride (ReC14)j in a combustion tube or the oxidation of rhenium trichloride (ReC13). The present paper describes a direct procedure which gives a superior product which needs only be vacuum distilled to remove dissolved chlorine. A limited number of physical properties of rhenium oxychloride have been reported. In 1932 Bruke and Zieglerl described i t as a colorless liquid melting a t 4.5’, boiling a t 131O , and hydrolyzing immediately in air to perrhenic (HRe04) and hydrochloric acids. I n the following year Geilmann and Wriggej reported it to be light sensitive, turning purple in sunlight and becoming colorless in the
4258
JAMES
E.
VOl. 79
BOGGS AND ~ ~ U N Z IEL-CHEHABI R
Re207. (CIHSOP)r
125-1 45
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Reoa decomposition products T h e rhenium(V1) oxide is then allowed t o react with chlorine in a dry combustion tube between 160 and 190"
100-190 O 2Re03 Cla 2Re03C1 T h e yield obtained from these reactions is above 70";. The product is quite pure and is colored slightly yellow due to dissolved chlorine; this, however, may be removed readily by vacuum distillation leaving a clear colorless liquid boiling a t 128' (uncor.). Analyses for chlorine were 12.71 and 12.7151 as compared t o the theoretical value of 13.14LG. This slightly lorn value was caused by some hydrolysis in air during weighing. Some precautions are necessary in the handling of this compound. Rhenium oxychloride reacts immediately with mercury and with ordinary stopcock grease; therefore, it must be trapped before reaching the diffusion pump. Furthermore, a special stopcock grease such as "Halocsrbon grease" (Halocarbon Products Corporation) should be used to minimize the decomposition. Even this grease, however, caused some slight decomposition of the oxychloride leaving a purple colored substance, probably rheniurn(\'I) oxide (Re03 1. T o test the hypothesis t h a t the purple color was due to this oxide, some R e o s was dissolved in a small amount of the oxychloride. I t is interesting t o note t h a t a similar purple solution was formed. The rhenium oxychloride can be kept without decomposition in a greaseless sl-stem of glass, Kovar and Monel. I n this manner, we were able t o keep the liquid colorless for several weeks. Khenium oxychloride is extremely reactive t o x a r d mercury, silver and a large number of organic compounds. Carbon tetrachloride, however, was found t o be a good solvent, giving a clear, colorless, solution. T h e oxychloride does not appear to react with brass t h a t has been first chlorinated, or with stainless steel. The infrared spectrum of gaseous rhenium oxychloride was measured in a ten centimeter gas cell with potassium bromide windows, using a double beam Perkin-Elmer Recording Infrared Spectrometer Model 21. The spectrometer is shown in Fig. 1. Curve Aiis the absorption spectrum of the vapor in the ceil and curve B is t h e absorption spectrum of the cell after removal of the oxychloride. T h e vapor pressure as measured with a Bourdon gage is 4.5 f 0.5 mm. of mercury at room temperature. T h e vapor density of rhenium oxychloride at room temperature is 6.5 X 1OF g./ml. (average of two determinations). Assuming the ideal gas law, the experimental molecular weight was 268 g. compared to a theoretical value of 270 g.
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dark. In 1932 the microwave spectrum was studied by Amble, et aLj3who reported the structure as a symmetric top with an Re-C1 distance of 2.230 f p.004 A., and Re-0 distance of 1.i61 f 0.003 A., and the Cl-Re-0 angle as 108" 20' f 1'. Recently Eichhoff and Weigelg studied the Raman spectrum of rhenium oxychloride but encountered difficulty in photodecomposition of the sample. Some additional properties of this compound are reported in the present work.
Experimental Rhenium(T'I1) oxide (Relo;) readily is converted to rhenium(V1) oxide ( R e o a ) b y reduction with dioxane.1° T h e reactions are (8) E. Amble, S.I,. Miller, A. L. Schawlow and C . H . Towner, J . Chem. Phrs., 2 0 , 192 (1952). (91 H . J. Eichhoff a n d F. U'eigel, Z . u)zoyg. allgem. C h e m . , 2'75, 267 (195%). (10) L. F. Audrieth, Editor-in-chief; "Inorganic Syntheses," Val. 111. 1fcGraw-Hill Book C o . , S e w York, N.Y . , 1950, p. 180.
[CONTRIBUTION FROM
THE
LAFAYETTE,
ISDIANA
DEPARTMEXT O F CHEMISTRY, THEUSIVERSITY
OF TEXAS]
The Thermal Decomposition of Uranium Peroxide, U04.2H20 BY JAMES E. BOGGSA N D MVNZIR EL-CHEHABI RECEIVEDAPRIL 1, 1957 U04.2H20 decomposes slowly in the temperature range 90-195' t o form a different peroxide, U207. T h e rate of this reaction has been followed and the properties of U207, which has not been isolated previously, have been investigated.
Uranium peroxide, UO4.2H2O,has been known since 1876l and has been subjected to intensive investigation in recent years. Nevertheless, its constitution is still unknown, some authors considering it to be a true peroxide hydrate, others a peroxy acid, and others an addition compound of uranium oxide, U03.H202.H20. ( 1 ) T. Fnirley, C h e m .Vews, 33, 237 (1876).
The existence of one other peroxide of uranium, U207, has been suggested. Evidence for a hydrated form of this substance was found by Hiittig and von Schroeder2in their experiments on the decomposition of hydrated UO4. Later, Kraus3 ob( 2 ) G. F. H u t t i g a n d E. von Schroeder, Z . n n o r g . allgem. C h e m . , 121, 243 (1922). (3) C . A. Kraus, M a n h a t t a n District Project Report A-281, Sept. 7 . 1942.
