hl. J. SIENKO
5556
VOl. s1
from the Redlich-Tellcr product rule3 since this rule gives the product of the ratios of the frequencies of the isotopically substituted niolecules for each vibrational frequency and since the frequency must remain the same or increase on substitution of a lighter isotope. The observed frequency ratios for the isotopic molecules are
require violation of classical valences, have been tentatively rejected. If the Cz model is correct, there should be nine infrared active fundamentals of which only five have been observed. The remaining four frequencies almost certainly belong to weaker bending modes and might be below the limit of detectability.
1389/1318 = 1.053 1010/980 = 1.050 952/915 = 1.040 906/855 = 1.060 605/599 = 1.010
Visible and Ultraviolet Spectra of B2S3.-The electronic spectrum of the gas over B ~ S aJ t 1000° was investigated in absorption from 3000 to 7400 A. with a Bausch and Lomb 1.6 meter grating A No. 2 photoflood and a xenon arc were used as light sources. Bands were obstrved in the regions 5400-7200, 39004200 and 3100-3500 A . Tlie red band system bears a t least a superficial resemblance to the green system of BsOa.
If the frequencies observed are ~~undamentals of
B&, then i t can be shown that the D,t, and Dmf, structures are inconsistent with the observed shifts. The C2\.point group is not eliminated directly by the product rule. However, the most plausible assignment of the observed frequencies seems to favor the CZstructure as the only chemically sound structure which is consistent with the observed isotope shifts. Other models, which (8) G . I-IerLberg. “Infrared and Rariian Spectra.” 11. Van Nostrand Co., Inc., S e w York, N.Y.,1 9 5 .
[cO\ r R I l J L I I U \ I RORI 1 I I F
Acknowledgment.-This work was in part supported by the Callery Chemical Company under a contract from the Bureau of Aeronautics, Department of the Navy. MADISON, WISCONSIX
BAKERL A U O R A r O R Y
OE CEIEMISTRY, CORUELL UNIVERSITY]
Thallium-Tungsten Bronze : A Solid State Defect Structure1 BY A I . J. SIENKO RECEIVED APRIL 29. 1969 Thallium-tuiigsteti bronzes, Tlz\V03, have been prcp:rred ranging in composition from x = 0.19 to x = 0.36. Preparation methods included: (1) heating T l ~ n ‘ O ~Li’O:$ , and W ; ( 2 ) vapor phase reaction of T1 and WOa; (3) electrolysis of TlzC03 Znri 1 ’03mixtures. Prnducts were crystallinc and powder diagrams could be indexed in the tetragonal system with a = I .31 and’c = 12.50 A . Electrical resistance 1ne;tsurements using a potential probe method on single crystals indicated inctallic conduction with specific resistivity varying from 0.0 X l o w 3ohiri-cm. a t 25’ t o 9.0 X ohm.cm. at 240”. Thermoelectric power a t rnoiri temperature was -20 microvolts per degree referred to platinum, suggesting one free electron per thallium atom. A general model is proposcd for the tungsten bronzes M,\\‘Os where M is viewed as giving rise t o local energy levels in the forbidden gap between the conduction and valence bands of OS.
1.
The tungsten bronzes,2hl,IVO3, in which M is a univalent metal and x lies between 0 and 1, represent an unusually interesting series of non-stoichiometric materials with properties ranging from metallic to semi-conducting depending on what M is. If h l is sodium, the resulting sodium-tungsten bronze shows a linear increase of resistance with temperature and a Hall coefficient corresponding to one free electron per sodium atom3; if hl is copper or silver, the resulting tungsten bronze shows an exponential decrease of resistance with rising t e m p e r a t ~ r e . ~I n both cases, magnetic susceptibility is low and independent of temperature. I n attempting to set up a general model to account for these observations, we have been led to reject the older view of pI‘Iz\VOa as a solid solution of WOa in hypothetical M W 0 3 in favor of a model in which ?rl,b’O~ is viewed as a solid solu(1) This research was supported in whole or in part by the United States Air Force under Contract No. AF 19(ti38)-101 monitored b y the AP Office of Scientific Research of the Air Research arid Development Command. ( 2 ) S e e , fc,r ex,Ltuple, ti. I I i g f i , %. p h y s i k . C h e m . , B29, 1!1% ( 1 5. Straumanis and S. S. Hsu, THISJ O I I K N A L , 72, 4027 (1 lagneli a n d R. nlomberg, Acta Chum. Scand.. 5 , 377 ( 1 Conrijv , ~ i ! < l‘1 I
