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70 1
(3) ULODGETT,K. B.: J. Am. Chem. SOC.67, 1007 (1935). l(1)HLODGETT, K. B., A N D LANGMUIR, I.: Phys. Rev. 61, 964 (1937). (5) GERMIER, I,. H . , A N D STORKS, K. H.: J. Chem. Phys. 6, 280 (1938). 16) GERMER, L. H . : Phys. Rev. 66, 58 (1939). 17) GORANSON, R. W., A X D ZISMAN, W. A , : J. Chem. Phys. 7, 492 (1939). (8) HARKER,D.: Unpublished paper. I O ) HOLLEY, C., A N D BERNSTEIN, S.: Phys. Rev. 62, 525 (1937). (10) IASCUUIR,I.: Science 87, 493 (1938). (11) LhNGMUIR, I.: J. 4m.Chem. SOC. 60, 1190 (1938). (12) ~ l h I i ( ; M U I R , I.: Cold Spring Harbor Symposia Quant. Biol. 6, 171 (1938). (13) LASGMUIR,I., SCHAEFER, V. J., A N D SOBOTKA, H.: J. Am. Chern. SOC.69, 1751 (1937). (14) L.ANGMUIR, I., A N D SCHAEFER, V. J.: J. .4m. Chem. SOC.69, 2400 (1937). (15) LASGXUIR, I., A N D SCHAEFER, V. J.: J. Am. Chem. Soc. 69, 1762 (1937). (16) LANGMUIR, I., A N D SCHAEFER, V. J.: J. Am. Chem. SOC.80, 1351 (1938). I., A N D SCHAEFER, V. J.: Chem. Rev. 24, 181 (1939). (17) LANGMUIR, (18) LUCKIESH, M., A N D TAYLOR, A . H.: Lighting Research Laboratory, General
Electric Company, Nela Park, Cleveland. (19) SORTON, F. J.: J. rim. Chem. SOC.61, 3162 (1939). E. F., A N D WYMAN, J.: J. Am. Chem. SOC.60, 1083 (1938). (20) PORTER, (21) PORTER, E. F., A N D WYMAN, J.: J. .4m. Chem. SOC.60, 2855 (1938).
THE ISOTHERlfAL DEHYDRATIOS OF HEAVY-METAL IROX CYANIDES' HARRY B. WEISER, W. 0. MILLIGAX,
AXD
J. B. BATES
Department os Chemzstry, The Rice Instatute, Houston, Texas Recezved October 15, 1940
The heavy-metal ferro- and ferri-cyanides are frequently assigned formulas which suggest that they form definite hydrates. For example, early investigators have claimed 10 (17), 7 (9), 6 (17), and 3 (2, 11) moles of water to be combined with 1 mole of cupric ferrocyanide under various conditions. Lowenstein (4) observed a continuous loss of water from the cupric ferrocyanide gel dried over varying concentrations of sulfuric acid. Hartung (2) obtained a few points on an isotherm for the dehydration of cupric ferrocyanide by the time-honored method of van Bemmelen, but recognized the uncertainty of reaching equilibrium because of air in the apparatus. More recently, Kcggin and Miles (3) considered it possible, from an s-ray diffraction study of various iron cyanide compounds, that water molecules may be present in the unit cell. Rigamonti (10) did not assume
* Presented at the One Hundredth Meeting of the American Chemical Society: held at Detroit, Michigan, September 9-13, 1940.
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H. B. WEISER, W. 0. MILLIGAN, AND J. B. BATES
any combined water within his similar proposed structure for cupric ferrocyanide. The present authors (15) obtained almost identical x-ray diffraction patterns for the ferrocyanide gels of copper, cobalt, nickel, and manganese. It waa assumed that these compounds are isomorphous, and that the relatively large ferrocyanide anions are so arranged as to give channels
PWSSURE, cn
OF
OIL.
PRESSURE, cu. OF OIL.
FIG.1 (left) : Dehydration isotherm for cupric ferrocyanide FIG.2 (right) : Dehydration isotherm for cupric ferricyanide
PRCSSUREI CM. oc OIL.
PRESSURE+ CU. OF OIL.
FIG. 3 (left): Dehydration isotherm for Prussian blue FIQ. 4 (right): Dehydration isotherm for Turnbull’s blue
in which the smaller metal ions are grouped. A quantitative structure haa been suggested for several heavy-metal ferricyanides by van Bever (12), who believes that there are a t least 2 or 3 moles of combined water per mole of ferricyanide. Pauling (8) has called attention to unpublished data by Elliott, which indicate that certain iron-cyanide compounds are actually KMFe(CN)a. H10 (M = manganese, cobalt, or nickel) possessing a structure similar to that proposed by Keggin and Miles and by van Bever.,
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703
It has already been reported (6) that the x-ray diffraction pattern of cupric ferrocyanide gel agrees with the electron diffraction pattern obtained by Fordham and Tyson (1). It follows that, if the cupric ferrocyanide gel is a definite hydrate, it must be stable in the high vacuum of the electron diffraction apparatus. Because of the uncertainty as to the state of water in the heavy-metal ferro- and ferri-cyanides and its possible bearing on the quantitative
Fro. 5. Eleotron diffraction pattern for cupric ferrocyanide
structure of the compounds, an isothermal dehydration study h a j been made of the following typical examples of these classes of complex salts: cupric ferrocyanide, cupric ferricyanide, Prussian blue, and Turnbull's blue. EXPERIMENTAL
Preparation of samples Samples of cupric ferro- and ferri-cyanides, Prussian blue, and Turnbull's blue were prepared by the addition of an excem of a solution of the heavymetal chloride to potas8ium ferrocyanide or potassium ferricyanide solu-
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H. B. WEISER, W. 0. M I L L I M N , A N D I. H. BATES
tions. Thr resulting gels were washed with distilled water hy means of a centrifugc until the supernatant liquid was frce of chloride ions, and were airdried at room tcmperature. Dehydration isotherms
The isothermal dehydration of thc lianiplcs was carried out, in an apparatus already described (13, 16). The general procedure consisted in
FIG. 6. Election ditiraction pattorn for Prussian Moo
pumping o f f a definite amount of water and measuring t,he vapor pressure by means of a manometer fillcd with v a ~ u u mpump oil of dmsity 0.93 (25°C.). Tlic cornpositioii of the sample was followcd'by means of t,he McHain- Ihkr balanw (5). Thc 2 or 3 br. requirrd for equilihrium is rrlat,ivcly short,, sirire t,he amount of air remaining in the appara.tus is small. The isotherins for cupric ferrocyanide, cupric lerricyanide, Prussian blue, and Turnbull's hlut: are giwn in figure8 1, 2, 3 , and 4, respcebively.
DEHYDRATION OF HEAVY-METAL IRON CYANIDES
705
In separate experiments carried out in the dehydration apparatus, it was observed that all the water was removed from cupric ferrocyanide a t 25OC. in the vacuum produced by a Hyvac pump.
Electron diflraction analysis Electron diffraction patterns were obtained (14) for cupric ferrocyanide and Prussian blue gels. The patterns are reproduced in figures 5 and 6. It was found that the patterns did not changeafter thesamples were exposed t o the high vacuum of the electron diffraction apparatus for periods as long as 24 to 48 hr. ; the experiments referred to in the previous paragraph show that all the water wcts removed by a lower vacuum in a shorter time. DISCUSSION
The continuous dehydration isotherms for the gels of cupric ferrocyanide, cupric ferricyanide, Prussian blue, and Turnbull’s blue indicate that no definite hydrates of these materials are formed. Most of the water present in the samples is adsorbed on the surface of the finely divided crystals, but some may be held by adsorption forces within the channels in the lattice between the relatively large ferrocyanide or ferricyanide ions, after the manner of certain zeolite crystals that do not contain water molecules in definite chemical combination (7). The quantitative agreement between the electron diffraction pattern obtained in a high vacuum and the x-ray diffraction pattern of the hydrous cupric ferrocyanide gel is independent evidence that the heavy-metal iron cyanides are not definite hydrates. The possibility is not precluded that other ferrocyanides or ferricyanides not examined may be definite hydrates. SUMMARY
The following is a brief summary of the results of this investigation: 1. The continuous dehydration isotherms obtained for the gels of cupric ferrocyanide, cupric ferricyanide, Prussian blue, and Turnbull’s blue indicate that these materials are not definite hydrates. 2. The electron diffraction pattern for cupric ferrocyanide obtained in a high vacuum is identical with the x-ray diffraction pattern of the moist gel. This is independent evidence that the cupric ferrocyanide gel is not a definite hydrate. 3. Future quantitative x-ray diffraction studies of the structure of the heavy-metal iron cyanides should take into account the fact that, in general, these materials do not contain water in definite chemical combination. REFERENCES (1) FORDHAM AND TYSON: J. Chem. SOc. 1937, 483. (2) HARTUNG: Trans. Faraday SOC.16, Part 3, 160 (1920). (3) KEGGIN AND MILES:Nature 137,577 (1936).
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(4) L~WENSTEIN: 2.anorg. allgem. Chem. Bs, 125 (1909). (5) MCBAINAND BAKR:J. Am. Chem. SOC.48, 690 (1926). (6) MILLIQAN: In Weiser's Inorganic Colloid Chemistry, Vol. 111, p. 308. John Wiley and Sons, Inc., New York City (1938). (7) MILLIQAN AND WEISER:J. Phys. Chem. 41, 1037 (1937). (8) PAULINO:The Nature of the Chemical Bond, p. 111. Cornel1 University Press, Ithaca, New York (1939); RICHARDSON AND ELLIOTT: J. Am. Chem. SOC. 62.3182 (1940). (9) RAMMELSBERO: Pogg. Ann. 78, So (1848). (10) RIQAMONTI: Gasz. chim. ital. 67, 137, 146 (1937). (11) TINKER:Proc. Roy. 500.(London)M A , 268 (1917). (12) VAN BEVER:Reo. trav. chim. 57, 12.59 (1938). (13) WEISERAND MILLIQAN: J. Phys. Chem. 39,% (1935). (14) WEISERAND MILLIQAN: J. Phys. Chem. 44, 1081 (1940). (15) WEISER,MILLIQAN, AND BATES:J. Phys. Chem. 4, 945 (1938). (16) WEISER,MILLIQAN, AND COPPOC: J. Phys. Chem. 43,1109 (1939). (17) WYROUBOFF: Ann. chim. phys. I518,444(1876).
LIQUID-VAPOR COMPOSITION OF T H E BOILING TERNARY SOLUTION ETHYL ALCOHOGGLYCEROL-BENZENE
HUGH J. McDONALD Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois Received September 88, 1040
The relationship between the composition of a solution and the vapors evolved when it is distilled are important in the industrial separation of its components and in the theory of solutions. Although a large number of investigations dealing with binary solutions have been published, comparatively little work has been done on ternary solutions. Owing to the interest displayed, during the last few years, in the problem of the separation of the pure components from mixtures of ethyl alcohol with other substances, it waa thought that an investigation of the liquid-vapor composition data for a system made up of ethyl alcohol and glycerol, with a third component miscible with one of them, would prove to be interesting. I n this investigation a study is made of the liquid-vapor composition of the ternary solution ethyl alcohol-glycerol-benzene. DISTILLATION APPARATUS
A retort of 400-c~.capacity, opening into a tapered side tube about lt in. in diameter at the large end, waa used aa the distillation vessel. The side tube waa fitted with a water condenser, and the upper part of the retort
