K. K. KELLEY,S. S. TODD AND C. H. SHOMATE
1350
perimentally obtained diffusion currents and thus offer an expilanation for the anomalous diffusion current constant in the case of samarium. Acknowledgment.-This work was undertaken while one of us (A. T.) held a graduate college research assistantship at the State IJniversity of Iowa. Summary Solutions of samarium chloride and sulfate were studied polarographically without supporting electrolyte and in the presence of lithium chloride, potassium chloride and tetramethylammonium
[CONTRIBUTION FROY
THE
Vol. 70
iodide. Addition of sulfuric acid to the sulfate solutions stabilized the half-wave potential. With one m o l a r samarium ion, in 0.001 normal sulfuric acid, 0.1 molar tetramethylammonium iodide and 0.01% gelatin medium a two step polarogram was obtained. The half-wave potentials were - 1.80 and - 1.96 volts against the saturated calomel electrode. The diffusion currents were, respectively, 6.0 and 13.0 microamp., corresponding to Sm+++ --+ Sm++, and Sm++ --t Smo. However, in 4 millimolar solution the behavior is anomalous. IOWACITY,IOWA
RECEIVED JUNE9, 1947
PACIFICEXPERIMENT STATION, BUREAUOF MINES, UNITEDSTATES D E P A R T ~OF N TTHE INTERIOR]
Heat Capacities at Low Temperatures and Entropies of 3Ca0*Bz03,2CaO*Bz03, CaO*B,03,and Ca0.2BzO3l BY
K. K. KELLEY,~ s. s. T O D DAND ~
c. H. SHOMATE4
In a recent paper, Torgeson and Shomate6pre- Shomate,6 this material contained 0.42% of insented data for the heats of formation of the crys- soluble impurity from superficial reaction with the talline calcium borates, 3Ca0 BzOa 2Ca0 BaOa, nickel crucible in which it was prepared. No corCaO-B20s, and Ca0.2BaOs. These are all the rection for this impurity was made in the present compounds in the CaO-BaOs system, according to results. Heat Capacities.-The heat capacities were the work of Car1son.G The present paper reports low temperature heat capacity and entropy deter- measured by means of previously described' appaminations of these same substances, thus enabling ratus and methods. The results, expressed in dethe calculation of their free energies of formation. fined calories,* are listed in Table I and shown There are no previous similar data for any of these graphically in Fig. 1. The molecular mass figures in the headings of Table I accord with the 1947 compounds. Materials.-The samples of calcium borates International Atomic Weights? The precision used in the present measurements were vir- error in the results is under 0.1% and it is believed tually the same as those employed in the heat of they are accurate on the average to within *0.3y0 formation studies of Torgeson and S h ~ m a t e . ~in the absolute sense. The heat capacities of all four calcium borates Their paper included the method of preparation of the samples, their densities, and X-ray diffrac- are higher at the lower temperatures, and lower a t tions, and repetition here appears unnecessary. the higher temperatures, than the sum of the heat About one mole of each compound was used in the capacities of the component oxides. The greatest present measurements and all weighings were cor- average deviation from additivity is shown by rected to vacuum. The chemical purity of the Ca0.2B20s, the heat capacity of which averages samples is indicated by the following analyses : over 2 cal. per deg. per mole lower than the sum of the heat capacities of the component oxides in the Actual analysis Theoretical analyses temperature range 100 to 298.16'K. In this conCaO, % CuO, % Bz01,% Substance B2O8, % nection it is of interest to note that this substance 70.72 29.28 70.75 29.31 3CaO.BzOa also has the highest atomic density (lowest mean 2CaO.BzOa 61.71 38.41 61.69 38.31 atomic volume). Other things being equal, high CaO.BrO3 44.59 55.26 44.61 55.39 atomic density generally parallels low heat caCa0-2Bz03 28.57 71.02 28.71 71.29 pacity a t low temperatures. Only the calcium diborate contained any appreEntropies at 298.16"K.-In each instance, the ciable impurity. As mentioned by Torgeson and entropy increment between 52.00 and 298.16'K. (measured portion, Table 11) was obtained, as (1) Published by permission of the Director, Bureau of Mines, U. S. Department of the Interior. Not copyrighted. usual, by numerical integration of a large-scale (2) Supervising Engineer, Pacific Experiment Station, Bureau of plot of C, against log T. To obtain the entropy Mines.
-
(3) Chemist, Pacific Experiment Station, Bureau of Mines. (4) Formerly chemist, Pacific Experiment Station, Bureau of Mines. (5) Torgeson und Shomate, THISJOURNAL, 69, 2103 (1947). (6) Carlson, Bur. Standards J . &scorch, 9, 826 (1932).
(7) Rellcy, Naylor and Shomate, Bur. M i n e s Tech. Paper 686 (1946). (8) Mueller and Rossini, A m . J . Phys., 19, 1 (1944). (9) Baxter, Guichard and Whytlaw-Gray, THISJOURNAL, 69, 731 (1947).
April, 1948 TABLE I
MOLAL HEATCAPACITIES T,OK.
C p , cal./deg.
T, OK.
Cp, cal./deg.
3CaO*B203(mol. wt., 237.88) 5.978 165.5 6.827 175.5 7.806 185.6 8.863 195.9 9.932 205.9 11.13 216.2 12.21 226.2 14.02 235.8 16.56 246.1 18.92 256.1 21.34 266.1 23.47 276.2 25.45 286.1 27.39 296.3 29.07 (298.16)
30.66 32.13 33.52 34.82 36.09 37.23 38.28 39.27 40.35 41.29 42.22 43.18 43.82 44.77 (44.90)
57.0 61.1 65.5 69.8 74.1 78.4 85.6 94.8 104.5 115.2 125.Z! 135.1. 145.4 155.5
2CaO*B@s(mol. wt., 181.80) 4.914 165.7 5.695 175.6 6.522 185.8 7.399 195.9 8.295 206.2 9.191 216.2 10.06 226.0 11.49 235.8 13.27 246.2 15.03 256.2 16.87 266.5 18.46 276.2 19.96 286.1 21.37 296.5 22.67 (298.16)
23.91 25.04 26.10 27.10 28.08 29.00 29.84 30.60 31.43 32.30 33.07 33.71 34.39 35.03 (35.16)
54.4 56.9 57.7 60.4 61.8 64.4 68.5 71.2 72.6 75.6 80.8 84.8 94.0 104.2 114.3 124.3 135.3
CaO*B~Os (mol. wt., 125.72) 4.199 145.5 4.554 155.6 4.679 165.8 5,064 179.1 5.265 185.6 5.634 195.8 6.220 205.4 6.604 216.0 6.795 226.1 7.233 235.4 7.924 245.2 8.455 255.6 9.580 265.5 10.80 276.1 11.93 286.4 12.96 296.3 14.02 (298.16)
14.93 15.81 16.68 17.70 18.15 18.87 19.58 20.21 20.84 21.40 21.98 22.55 23.16 23.73 24.24 24.78 (24.85)
54.2 57.5 61.6 66.6 71.5 76.3
C~O-~B& (mol. J wt., 195.36) 4.583 165.7 5.092 175.9 5.742 189.0 6.558 196.0 7.366 206.3 8.148 215.9
52.8 56.6 60.6 64.0 69.0 73.5 77.7 84.7 94.8 104.6 115.1 125.1 135.1 145.7 155.5 53.0
1351
HEATCAPACITIES OF VARIOUS CALCIUM BORATES 226.4 235.8 245.6 256.0 266.0 276.2 286.5 296.5 (298.16)
8.998 9.776 11.07 12.65 14.22 15.67 17.42 18.90 20.31
81.4 86.3 94.4 104.5 114.6 124.1 135.9 146.0 155.8
29.61 30.74
31.88 33.20 34.30 35.33 36.42 37.56 (37.75)
0
50 100 150 200 250 300 Temperature, OK. Fig. 1.-Heat capacities: A, Ca0.B20s; B, Ca0.2BnOs; C, 2CaO.BaO:; D, 3CaO.BzOs.
increments between 0 and 52.00°K., the measured heat capacities were fitted with the following combinations of Debye and Einstein functions, the maximum deviation between measurements and function sums being shown in parentheses
2Ca0.B20a 3 D ( y ) Ca0.B20s 2 D ( y ) CaO.2BaOs 3 D ( y )
+ 3E(?) + 3 E ( y ) +2E(y) f 3 E ( y ) +4E(Y) + 3 E ( y )
(1.0%) (1.0%)
These function sums were employed in obtaining the extrapolated portions of the entropies in Table 11. The extrapolated portion constitutes TABLE I1
ENTROPIES AT 298.16'K., CAL./DEG./MOLE 3CaO.BzOa 2CaO.BzOa CaO.Bz0a
21.75 23.11 24.84 25.76 27.07 28.31
(0.5%)
0 "-52.00 OK ., (extrapolation) 2.16 52.00'-298.16 OK., (measured) 41.73 S,",,.,, 43.9 * 0.3
Ca0.2B20s
1.84
1.65
1.59
32.84 34.7 * 0.2
23.41 25.1 * 0.2
30.61 32.2 * 0.3
1352
DAVIDPRESSMAN, JOHN H. BRYDEN AND LINUSP A U L I N G
only 6.6oJ, of the total entropy for Ca0.B203and is lower for ‘the other substances. The entropies of 3CaO-Bz03, 2Ca0.Bz03, and CaOeB203 differ, in order, by 9.2 and 9.6 units, corresponding to successive decreases of one mole of calcium oxide. These figures are to be compared with the measured value for free calcium oxide,l0 ggsl 6 = 9.5 0.2. This type of approximate additivity of entropies of some interoxidic compounds has been noted previously in work of this Laboratory and is the result of compensation of plus and minus deviations from additivity of heat capacities. In the case of CaO. 2B203 such compensation is quite incomplete and the entropy difference between Ca0-2BzOsand Ca0.B203 is only 7.1 units, whereas the entropy of crystalline boric oxide” is .$’g,l, = 13.0 * 0.1. Related Thermal Data.-Free energies of formation a t 298.16OK. of the four calcium borates from the oxides and from the elements are given in Table 111, being obtained from the relationship AFO = AH - TAS. The heats of formation, Aff298.16, are from the paper of Torgeson and Shomate.6 The entroDies emdoved in calculation of the As238.16 values are from publications of Kelley.lO3 l1 Precision uncertainties have been assigned to the free energies of formation from the oxides. It is not possible to do this for the values from the elements bec,ausethe probable error in the heat of (10) Kelley, Bur. Mincs Bull., 434 (1941).
TABLE I11 FREEENERGIES OF FORMATION AT 298.16’K., CAL./MOLZ From oxides Substance 3CaO.BzOs 2CaO.Bz01 CaO.BzO8 CaO.2BzOs
f
3CaO.BnOt 2CaO.BnOl CaO,BzOa Ca0,2BzOs
THE
GATESAND
CRELLIN
ASz0s.i~
AH2o3.16
-60,000 -45,760 -29,420
-
-42,930
1
40
* 30 1
*
20 20
-858,200 -692,100 -524,000 -880,200
2 . 4 * 0.7 2 . 7 * 0.5 2.6 * 0 . 3 -3.3 * 0.5 From elements-136.4 1 0.6 -111.2 1 0 . 5 86.3 t 0 . 5 -156.2 * 0.9
-
Aflo8.1~
-60,720 -46,570 -30,200 -41,950
-
* 210
* * *
150 90 150
-817,500 -659,000 -498,300 -833,700
formation of crystalline boric oxide, on which the free energies depend, is not known. The free energy of formation values from the oxides follow a normal pattern. The formation of Ca0.B203from the oxides gives a decrease in free energy of 30,200 cal. Smaller decreases in free energy accompany each successive step of adding one mole of oxide to CaO.BzOato form the other calcium borates. Summary Low temperature heat capacity measurements of 3Ca0. BzO~, 2Ca0 Bz03, CaO Bz03, and CaO 2BzOs were made throughout the temperature range 52’ to 298.16”K. The entropies of the four calcium borates were determined as 43.9 * 0.3, 34.7 * 0.2, 25.1 f 0.2; and 32.2 * 0.3 cal./deg./mole, respectively. Free energy of formation values from the oxides and from the elements are included.
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9
BERKELEY,CALIFORNIA
(11) Kelley, T i m JOURNAL, 68, 1137 (1941).
[ CONTRlBUTIOhl FROM
Vol. 70
LABORATORIES OF CHEMISTRY, No. 11541
RECEIVED OCTOBER 24, 1947
CALIFORXIA INSTITUTE OF
TECHNOLOGY,
The Reactions of Antiserum Homologous to the p-Azosuccinanilate Ion Groupla BY DAVIDPRESShfAN,lb
JOHN
H. BRYDEN AND LINUS PAULING
It was discovered by Landsteiner and van der Scheer2 that the precipitation of azoprotein containing the p-azosuccinanilate ion haptenic group by hapten-homologous antiserum (anti-S9 serum) is inhibited just as well by maleate ion as by succinate ion, whereas fumarate ion is practically ineffective, and from this observation the cautious conclusion was drawn3r4that “Accordingly, one could suppose that the succinic acid molecule can exist in a form corresponding to the cis configuration, or that the antibodies adjust themselves to (1s) The Serological Properties of Simple Substances. X I I I . For No. X I 1 of this series see D. Pressman, A. L. Grossberg, L. H. Pence, and L. Pauling, THISJOURNAL, 68, 250 (1946). (lb) Present address: Sloan-Kettering Institute for Cancer Research, New York. (2) K. Landstemer and J. van der Scheer, J. Expll. M e d . , 69, 751 (1934). (3) K. Landsteiner, “The Specificity of Serological Reactions,” Charles C Thomas, Springfield, Illinois, 1936, p. 129. (4) K. Landsteiner, “The Specificity of Serological Reactions,” Revised Edition, IIarvard University Press, Cambridge, Mass., 1945, p. 192.
this.” Because of our interest in the use of immunochemical techniques for the determination of the configuration of molecules and haptenic groups,~ we have extended our quantitative studies of hapten inhibition of serological precipitation to include the S p system, and have investigated the effect of over fifty haptens on the precipitation of Sp-ovalbumin and anti&, serum. The analysis of the data has shown that the normal configuration of the p-azosuccinanilate ion group in aqueous solution is a cis configuration, presumably stabilized by a hydrogen bond, and has provided information about the configuration of other ions. Experimental Methods Haptens.-The following substances used in this work have been described previouslp : succinanilic acid, p aminosuccinanilic acid, p-nitrosuccinanilic acid , and d(5) D. Pressman, Rcgisfcr of P h i Lambda Upsilon, 29, 30 (1944). (6) D. Pressman, J. H. Bryden, and L . Pauling, THIS JOURNAL, 6’7, 1219 (1945).
