INDUSTRIAL A N D ENGINEERING CHEMIXTRY
404
conditions per gram of water, is plotted against temperature. Figure 5 presents the solubility isotherms a t several temperatures. Figure 6 is t,he usual representation of the thermal characteristics by plotting the logarithm of the solubility coefficient against the reciprocal of the absolute temperature. T a b l e XI-Henry’s Law Constant ABSORPTION FUGACITY TEMP. PRESSURECOEFFICIENT K v Aim. Afm. c. 100 1.46 0.0146 97.43 0
Kf
200 300
3.19 3.60
0.0160 0.0120
195.4 302.6
0.0150 0.0163 0.0119
50
100 200 300
1.003 2.49 2.99
0.0100 0.0125 0.0150
101.0 207.0 326.5
0,0099 0.0120 0,0092
80
100 200 300
0.934 2.27 2.86
0.00934 0.0114 0.0143
102.0 212.5 334.1
0.00915 0.0107 0.0086
100
100 200 300
0.954 2.25 2.91
0.00954 0.0113 0.0145
102.8 214.3 338.7
0.0094 0.0105 0.0086
169
100 200 300
1.08 3.29 3.83
0.0108 0.0185 0.0128
104 217.8 344.0
0.0104 0.0151 0.0111
viscosity and suggested also that the thermal expansion of the solvent as measured by its specific volume change with temperature was a factor opposite in effect to viscosity. As a result these opposing factors a t some point neutralized each other and a minimum solubility point resulted. Careful study of these properties has convinced us that, while qualitatively the idea seems sound, the quantitative application to a particular system doubtless involves other factors also.
ab5
Discussion of Results
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Figure 6-Logarithmic
The variation of these results from the ideal law of Henry is shown in Table I1 and Figure 5. The Henry constant calculated both for pressures in atmospheres and for fugacities shows wide variations and no significant trends. In attempting to explain the peculiar properties of this system, many theories have been tested. In general it seems best to attribute depaxtures from ideal behavior to some property of the solvent rather than to look for explanation in some peculiarity of nitrogen. I n this work the effects of solvent density, viscosity, internal pressure, surface tension, association, and compressibility were investigated with the help of such other data as were available. Interesting theories have been proposed from time t o time correlating one or the other of these solvent properties with solubility. Only one, however, has definitely recognized the existence of minimum solubility points for gases a t constant pressures. Winkler ( I 1 ) developed a relation connecting solubility and
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P l o t of Isobars for NitrogenWater
The results, in so far as fundamental solubility theory is concerned, lead one inevitably to the conclusion that many more data are necessary for complete understanding of these compressed systems. Literature Cited (1) Antropoff, v., 2. Elektrochem., 25, 269 (1919). (2) Bohr and Bock, A n n . phys. chem., 44, 319 (1891). (3) Cassuto, Nuooo cimcnfo, 6; 1903 (1913). (4) Estreicher, 2. physik. Chem., 31, 176 (1899). (5) Just, I b i d . , 37, 342 (1901). (6) Keyes and Dewey, M. I. T. Publication 179 (1927). (7) Larsen and Black, IND. END. CREM.,17, 715 (1925). (8) Porter, Bardwell, and Lind, Ibid.. 18, 1086 (1926). (9) Sander, 2. physik. Chcm., 7 8 , 513 (1911). (10) Travers, “Experimental Study of Gases,” p. 255, Macmillan, 1901 (11) Winkler, Z . p h y s i k . Chem., 9, 171 (1899). (12) Wroblewski, v . . W i d A n n . , 4, 268 (1879).
X-Ray Study of the Copper End of the Copper-Silver System’ Roy W. Drier DEPARTMBNT OI MEIALLUROP.MICHlQAN COLLBQE OF MIXINGAND TECHNOLOGY, HOUGHTON. MICH.
URING an x-ray investigation of the plastic deformation of copper, it was noticed that both the Hull and the Laue types of spectra contained lines other than those of copper. Upon analysis these were found to be lines from the silver spectrum. Inasmuch as the copper under investigation did not contain enough silver to be beyond the accepted solid-solution range for silver in copper, the appearance of the silver lines seemed quite worthy of investigation. Constitution diagrams (3, 4) of the copper-silver system all show that silver is soluble in copper up to about 5 per cent by weight. The diagram in the International Critical Tables has the silver-in-copper solubility line dotted from * Received June 26, 1930; revised paper received February 26, 1931.
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the eutectic temperature, 778” C., down to room temperature, indicating that such solubility is questionable. It is generally accepted that there are two types of solid solution. In the most common type the solute atoms replace the solvent atoms on the lattice of the solvent. Opinions differ as to whether the replacement is statistical or random, but whichever condition obtains the resulting solid solution is of the substitutional type. For a continuous series of solid solutions i t is necessary that the two pure components A and B crystallize on the same type of lattice. According to the additive law of Vegard (1) the lattice constant changes linearly with the composition in atomic per cent between the limiting values of the pure components. Copper and silver both crystallize on the face-centered
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