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F. X. HASSION, C. D. THURMOND A N D F. h.TILUMBORE
while significant, cannot be interpreted unambiguously. It may be due to the binding of water by the ion (the estra charge on the PTA ion compared to the STA ion may be a factor) or to an asymmetry i n the molecular shape, or to both. If the PW12Od2-' ion is asymmetric, a profound change in struct'ure from that of the essentially spherical13H3PWln040.5H20acid is suggested. For PMA, it is not possible to define the nature of the species in solution with certainty. The facts that, in diffusion, the solute is clearly heterogeneous; the solutions eshibit a basicity near 7 ; and PMA-1 and PMA-2 are indistinguishable in sedimentation or diffusion, suggest that a t pH 4.5 the (13) J. F. Keggin, Proc. Rov. Soc. (London), 144A, 75 (1934); R. Signer a n d H. Gross, Helu. Chim. A d a , 17, 1076 (1934).
Vol. 50
principal species is P'\iV11039-7, along with some decomposition products. If, as a first approximation, V for PIL'IA-1 is utilized in conjunction with the extrapolated sedimentation and diffusion coiistants for PMA, the calculated molecular weight agrees with the expected value (Table V) within experimental error. I n the previous paper, data obtained with STA were shown to conform closely with the Svedberg equation. With the assignment of the formula PWlsOa2-7to the PTA anion a t pH 4.5, the PTA data also provide a critical test of the Svedberg equation. These experiments demonstrate further that sedimentatioii and diffusion experiments may be useful in the elucidation of the structures of related compounds.
ON THE MELTING POINT OF GERMANIUM BYF. X. HASSION, C. D. THURMOND AND F. A. TRUMBORE Bell Telephone Laboratories, Inc., Murray Hill,New Jersey Received May 1 3 , 1 0 5 6
Conflicting values for the melting point of germanium can be found in the literature. The present experiinents indicate the true value to be 937.2 f 0.5" as obtained by Greiner and Breidt. Freezing points were obtained from cooling curve measurements on germanium melts under high vacuum, in contact with GeO2 or under atmospheres of Hz, He, NZ or A. Melting points were determined by a visual method for germanium samples which had been melted previously in contact with GeOz a t 1000°, or under vacuum or hydrogen. The freezing and melting points in all cases were the same within experimental error.
1. Introduction At least thirteen independent determinations of the melting point of germanium ranging from 925975" appear in the literature.'-l3 The most widely quoted value of the melting point of germanium is 958-959°.14-17 Recent reference works apparent,ly refer to the survey of IielleyL8who accepted the esperiniental results of Dennis, Tressler and Hance.2 This melting point is in
surprisingly poor agreement with more recent mexsurement's, as can be seen in Table I. Since 1929 the reported germanium melting points have all been between 93-1 and 913", when determined 11.y standard methods. l 9 TABLE I SUMMARY OF Gc MELTING POISTDETERMIXATIONS
n w , oc.
Methoda
Ref.
916 f 5 V-saturated with GeOl 1 958 ?C 5 V-H2 atm. 1 958.5 TA-HQ atm.; repeated fusions under Hz 2 959 ?C 5 V-HZ atm. 3 975 5 5 V-vacuum 3 925 TA-HZ atin.; before fusions under HZ 4 943 TA-HQ atin.; after 42 fusions under Ht 4 949 TA-HZ atin.; after 132 fusions under Hu 4 955 ?C 5 TA-H2 atin.; many fusions under HZ 5 940 T,~-HQ atm. 6 940 TA-vacuum 7 940-941 TA-HZ atin. 8 943 TA-HZ atm. 9 934.5 ? 10 937.2 =C! 0 . 5 T.4-He a h . 11 940 d= 1 . 5 T.4-vacuuin, A, K2 atin.; in contact 12 with GeOz; from HZfusion 965-9TO y 13 " V-visual; TA-thermal analysis, i.e., cooling and/or heating curves.
(1) W. Biltz, Z.anorg. allgem. Chem., 72, 313 (1011); C. A . , 6, 170 (10 12). (2) L. M . Dennis, IC. . ! I Tressler and F. E. Hance, J . A m . Ciieni. Soc.. 48, 2033 (1923). (3) J . H. Muller, E . F. Pike and A. I
