THE ATOMIC HEATS OF GOLD, PLATINUM AND ANTIMONY AT LIQUID HELIUM TEMPERATURES. BY K. G. RAMANATHAN, F.A.Sc. ANI) T. M. SR~IVASAN

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1 THE ATMIC HEATS F GLD, PLATINUM AND ANTIMNY AT LIQUID HELIUM TEMPERATURES BY K. G. RAMANATHAN, F.A.Sc. ANI) T. M. SR~IVASAN (Natinal Physical Labratry, New Delhi) Received Nvember 19, 1958 INTRDUCTIN THE specific heat f platinum was measured in the liquid helium range f temperature by Kk and Keesm as early as 1936 while that f gld was measured nly very recently by Crak et al. (1955). Apart frm these tw measurements n ther calrimetric data appear t be available fr these tw metals in the liquid helium range. Therefre, it was decided t btain fresh measurements with a view t prvide an independent check n the earlier data using the new vacuum calrimeter (Ramanathan and Srinivasan, 1955) develped in this labratry. Travis Andersn (1930) investigated the temperature variatin f the specific heat f antimny in the range 60 ~ t 300 ~ K. Belw this range, hwever, n data appear t be available. S, the investigatin f the temperature variatin f atmic heat f antimny in the liquid helium range was als carried ut with the purest available metal, using ur calrimeter. EXPERIMENTAL DETAILS The new vacuum calrimeter which is capable f an accuracy f ver 3 per cent. in the temperature range 1.2 t 4.2 ~ K. has been fuuy described in ah earlier cmmunicatin (Ramanathan and Srinivasan, 1955). The specimens f gld and platinum were supplied by Messrs. Jhnsn Matthey & C., Ltd., Lndn, in cylindrical frms with diametfical hles fr embedding carbn resistance thermmeters. The purity f the gld specimen is per cent. and it weighs gm. The platinum specimen is per cent. pure and weighs gr. The antimny specimen f mass gr. was cast ut f a Jhnsn Matthey sample f 99.6 per cent. purity. The resistance thermmeter (a 89 watt, 100 hms resistr manufactured by Speer Resistr Crpratin, U.S.A.) was calibrated against the 1948 vapur pressure-temperature scale (Van Dijk and Shenberg, 1949) and crrected t the 1955 scale (Van Dijk and Durieux, 1955)..~1 55

2 56 K. G. RAMANATHAN AND T. M. SRINIVASAN RESULTS Gld and Platiium.--Figures 1 (a) and (b) shw the variatin f the atmic heats f gld and platinum respectively in the liquid helium range f temperature. The atmic heats f these elements can be represented by the equatin Cv = at + bt 3, where ' a' and ' b' ate the cnstants crrespnding t 7 ~ 6 >r I- _0 ~~ p. ~. c / /~ ) / / ( "~'~ (b) fa) PLATINU GLD M 1.2 t I 2-0 l I 2.8 I ~ :3,6 I 4"0 TEMPERATURE FIG. 1. Variatin f atmic hcsts f gld and plafinum.

3 Atmic Heats f Gld, Platinum wzd Antimny 57 the electrnic and lattice cntributins and 'T' rature. is the abslute tempe- It is nticed frm the graphs that the specific heat f the mnvalent nble metal gld falls ff mre rapidly than the spectfic heat f the transitin metal, platinum. This indicates a much larger linear term in the specific heat equatin fr platinum and is cnsistent with the suppsitin f Mtt and Jnes (1936) that the unfilled 'd' band cntributes appreciably t the electrnic specific heats f transitin metals. The atmic heat cnstants f gld have been calculated by the methd f least squares frm the results in the range 1.3 t 4.2 ~ K. and are fund t be a = (1 " ) 10-4 b = ( ) 10-4 The Debye temperature calculated frm the 'b' value (b = 464.4/0 ~) is ~ K. and Similarly the cnstants f platinum are fund t be a = (t " 100) 10-4 b = ( ) = ~ K. The results f earlier wrkers tgether with urs ate given in Table I fr cmpa TABLE I Gld Platinum Purity~ ax104 0 ~ Purity~ ax104 0 ~ This wrk Crak et al Schultz (1954) Kk and Keesm (1936) "0 Burtn (1940) (S.H.) (S.H.) 225 (Res.) 175 (Res.) 240 S.H.--Value derived frm specific heat data. Res.--Value derived frm electrical rr by Gruneisen's frmula.

4 58 K. G. ~ATHAN AND T. M. SRL~IVASAN The electrnic specific heat cnstants and the Debye 0 values f gld and platinum f earlier wrkers shw general agreement with ur values. Antimny.--Figure 2 (a) shws the variatin f the atmic heat f antimny with temperature in the range 1.3 t 4.2 ~ K. Figure 2 (b) is a plt Id Q ~ 2!- I- j >r r --,'t f f T I I,, f,i i 2 3 T~ J < I I I I [ I i " ,.~b ~, 4 =J < 0 30 / hi Z 0 0 IC FIG. 2. I I, I I I I i TEMPERATURE (a) Valuatin f atmic heat f antimny in the temperature range 4"1-1 "3 r K. (b) Variatin f C/E s with tempr (c) Plt f CIT against T 2.

5 A tmic Heats f Gld, Platinum and Antimny 59 f Cv/T ~ against T. The regin where the electrnic cntributin becmes predminant appears belw 2 ~ K. Figure 2 (c) is a plt f Cv/T versus T 2 in this regin. The cnstants have been calculated by the methd f least squares frm all the measurements belw 2 ~ K. and are fund t be and a = ( ) 10-4 b = ( ) = ~ K. Burtn (1940) has calculated 0 as 201 ~ K. frm the specific heat data f Travis Andersn (1930). This is als in gd agreement with ur result. Str~a~Y The variatin f atmic heats f gld, platinum and antimny have been investigated in the liquid helium range f temperature (4.2 t 1-3 ~ K.). The atmic heats f these elements can be represented by the frmula Cv (Gld) [( ) T + ( ) T a] Cal./~ K. Cv (Platinum) = 10 4 [( )T + (0.337 :k 0.014)T a] Cal./~ K. Cv (Antimny) = 10 -a [(0.575 :k 0.041) T + (0.525! 0.013)T 3] Cal./~ K. ACKNWLEDGMENT The authrs are thankful t Sir K. S. Krishnan, F.R.S., Directr, Natinal Physical Labratry, fr bis kind interest in this wrk. Burtn, E. F., Gmysn Smith, H. and Wilhelm, J.. Crak, W. S. et al... Kk, J. A. and Kcesm, W. H. ]V[tt~ N. F. and Jnes, H... REFERENCES Phenmena at the Temperature f Liquid Helium (Reinhld Publishing Crpratin, New Yrk), 1940, p Phy. Rey., 1955, 98, Physica, 1936, 3, 1035; Leiden Cmm. N. 245(a). The Thery f the Prperties f Metals and Allys (xfrd University Press), 1936, p. 192.

6 60 K. G. RAMANATHAN AND T. M. SRINrVASAN Ramanathan, K. G. and Srinivasan, T. M. Schulz, L.G... Travis Andersn, C... Van Dijk, H. and Durieux, M. and Shenberg, D... Phil. Mag., 1955, 46, 338. Phy. Rey., 1954, 94, J. Ar. Chem. Sc., 1930, 52, Cmm. Cnference de Physique des Basses Temperatures, Paris, 1955, p Nature, 1949, 164, 151.

(Communicated at the meeting of January )

(Communicated at the meeting of January ) Physics. - Establishment f an Abslute Scale fr the herm-electric Frce. By G. BOR ELlUS. W. H. KEESOM. C. H. JOHANSSON and J. O. LND E. Supplement N0. 69b t the Cmmunicatins frm the Physical Labratry at