Broek, E.G. van den

Gellings, P.J.

Lith, H. van

English

van Lith, H.

van den Broek, E.G.

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Nature of the reaction products of Na(ℓ) with CrO3

University of Twente Research Information

INORG. NUCL. CHEM. LETTERS VoL 11, pp. 817-819, 1975. Pergamon Press. Printed in Great Britain. NATURE OF THE REACTION PRODUCTS OF Na(A) WITH CrO 3 H. van Lith, E.G. van den Broek and P.J. Gellings i Laboratory for Inorganic Chemistry and Materials Science, Department of Chemical Engineering, Technical University Twente, Postbox 217, Enschede, the Netherlands (Received 22 July 1975) The X ray diffraction patterns of the compound existing in liquid sodium in the presence of chromium and oxygen, found by many investigators (1,2,3,4) and in our laboratory are identical Most of the authors suggest this compound to be NaCrO 2. Addison and Barker (i), however, suggest the formula Na2CrO 3 for this compound. The patterns obtained by us, using CuKe radiation and a Debije-Scherrer camera of 114.7 mm diameter, are shown in the first two columns of Table i. TABLE 1 Diffraction Patterns of NaCrO 2 reaction Na(A) solid state Tech. Phys. Dienst calculated - d [ ~ [  I d l ~  [ I d l ~  I I d l ~  [ I 5.27 60 2.64 8 2.54 4 2.447 i0 2.152 100 1.697 4 1.567 20 1.485 30 1.405 2 1.356 4 1.303 6 1.235 6 5.33 100 2.657 40 2.540 40 2.449 40 2.161 100 1.707 40 1.575 70 1.487 70 1.433 40 1.335 40 1.328 40 1.298 40 1.264 20 1.224 40 5.32 70 2.662 20 2.542 20 2.451 40 2.164 100 1.707 i0 1.578 20 1.487 40 1.432 20 1.357 6 1.331 2 1.298 8 1.271 6 1.265 2 1.226 8 5.31 90 2.66 20 2.54 6 2.446 30 2.160 I00 1.704 i0 1.575 20 1.484 30 1.429 8 1.355 i0 1.328 2 1.296 10 1.269 4 1.262 4 1.223 i0 817 818 Reaction Products of Na(~) with CrO3 VoL 11, No. 12 In the first column of Table 1 the pattern of the product obtained from the reaction of CrO 3 with an excess of liquid sodium is given. The sodium is saturated with oxygen at the reaction temperature, being 320 °C. The reaction time was 14 days. Before analysing the product, the sodium is distilled off (400 °C, 10 -2 mm Hg during i0 hours). The pattern in the second column has been obtained on the product of the solid state reaction by Van Leuven (3): Na2CO 3 + Cr203 - ) 2 NaCrO 2 + CO2/m (powdered mixture heated at 900 °C in an argon atmosphere during two hours). The pattern in the third column has been obtained by the Tech, Phys. Dienst (4) on a product prepared by the same solid state reaction. The pattern shown in the last column has been calculated using the structural data, shown in Table 2, proposed by R~dorff and Becker (5) as mentioned by Wyckoff (6). Comparison of the different columns of Table 1 shows the agreement between the experimental and the calculated patterns. TABLE 2 Hexagonal Unit Cell of NaCrO 2. Space group R3--m - D 5 The 3d Na (0,0,0) Cr (0,0,½) O I (0,0,u) Oii (0,0,~) + ( 0 , 0 , 0 ) + ( 1 / 3 , 1 / 3 , 1 / 3 )  + (2/3,1/3,1/3) a = 2.968 ~ ; c = 15.94 ~ ; u = 0.22 Calculating the value of "u" using the patterns found by Addison et.al. (I), Gross et.al. (2), Van Leuven (3), the Tech. Phys. Dienst (4) and in our laboratory with a least squares refinement program by Rietveld (7) yields u = 0.220 ~ 0.015; in these calculations the Na + ion has the (0,0,0) position. This, therefore, also confirms the results obtained by R~dorff et.al. Because the diffraction pattern found by Addison et.al. (i) as mentioned by the A.S.T.M. Powder data file (8) agrees with other investigators (2,3,4) as well as with the patterns Vol. 11, No. 12 Reaction Products of Na(~) with CrO3 819 observed and calculated by us,  this shows that it is highly imporobable that the format ion  of his product as Na~CrO~ having the Li2SnO 3 s t ruc tu re  is cor rec t .  ACKNOWLEDGE MENT We a re  very  grateful  for  the a s s i s t a n c e  given by Dr .  J .  Bouwma with the computer  calcula t ions .  RE FERENCE S 1. C .C,  ADDISON and M.G. BARKER, J. Chem. Soc. ,  5534 (1965). 2. P. GROSS, G .L .  WILSON and W.A.  CUTTERIDGE, J. Chem. Soc. (A), 1908 (1970) 3. E.  VAN LEUVEN, M. Sc. thes is ,  Technical  Univers i ty  Twente, Enschede (1973). 4. Technlsch Physische Dlenst ,  TNO - TH, Delft, pr ivate  communicat ion.  5. W. RIYDORFF and H. BECKER, Z. Natur forsch . ,  9b, 614 (1954}. 6. R . W . G .  WYCKOFF, Crys ta l  S t ruc tures ,  Vol. 2, In te r sc ience  Publ i shers ,  New York (1964). 7. H.M. RIETVELD, Fys ica  lvmmo No.153, RCN, Pet ten,  The Netherlands (1968). 8. Am. Soc. for Tes t ing  Mater ia ls ,  F i le  No. 18 - 1209. 

Nature of the reaction products of Na(ℓ) with CrO3

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