I N D U S T R I A L A N D ENGINEERING CHEMISTRY
970
1 ‘
gives a pattern with the copper lattice practically identical with the supposed lattice of a silver-rich solid solution with the K, radiation, and there is little doubt that Drier’s conclusions are erroneous. CYRILSTANLEY SMITH RESEARCH LABORATORY AMEFUCAN BRASSCo. WATEREURY CONN. June 15, 1831
..............
Editor of Industrial and Engineering Chemistry: It is possible that, as Mr. Smith suggests, the spectral lines attributed to silver are due to a MoKB reflection from the copper lattice. It is more probable that the spectral lines are partially due to such cause, inasmuch as the x-ray spectrum of spectroscopically silver-free copper gave no evidence of the silver lattice. It is an unfortunate coincidence that a MoK, reflection from a silver lattice and a MoKb reflection from copper coincide so closely. At the time the work was done, molybdenum radiation was the only one available, for otherwise some other radiation would have been used in corroboration. Mr. Smith refers to Stockdale as being in direct disagreement with my conclusions. I n the paper by Stockdale referred to, Stockdale concludes, “ . . . . .at room temperature silver is almost insoluble in copper.” Mr. Smith, in “Constitution of Copper-Silver Alloys,” a paper prepared for the Nonferrous Data Sheet Committee of the Institute of Metals Division of the American Institute of Mining and Metallurgical Engineers, refers t o Hirose who states that the solubility of silver in copper decreases rapidly to a negligible amount at 500’ C. Manifestly, if it is negligible at 500” C., it is still less soluble at room temperature. In the same paper Smith states “both Erdal and Weinbaum have determined the solubility (of silver in copper) from crystal structure measurements but their results are not convincing.” This is the same reference he uses in criticizing my manuscript. The writer appreciates Mr. Smith’s critical efforts, but in view of the vast disagreement of the literature cited they do not seem t o be a t all conclusive. ROY W. DRIER DEPARTMENT OF METALLURGY MICHIGAN COLLEGE OF MININGAND TECHNOLOGY HOUGHTON, MICHIGAN July 2, 1931
Editor of Industrial and Engineering Chemistry: On page 710 [IND. ENG. CHEM.,23, 708 (1931)], Elizabeth W. Aldrich and Dale W. Querfeld say that “the boiling points of ethanol solutions are somewhat higher than those of methanol solutions having equal freezing points.” This statement is incorrect when speaking of solutions having freezing points between 0 ” and -15’ C. The data contained in this article are no doubt quite accurate, since, as the authors have indicated, they agree very well with other literature on the same subject. The error is that the abovementioned statement is not corroborated by either the prior literature or by the article in question. The following abbreviated table may be formed by making a few additions to Table 111, page 710 from data contained in Tables I and 11:
c. -5
- 10 - 15 - 20 etc.
ROILINGPOINT
Methanol-Water 0
c.
92.0 88.2 86.0 84.0 etc.
Ethanol-Water 0
These data vary slightly, depending upon the literature used as an authority, but in general it can be said that the boiling points of aqueous ethanol solutions are lower than those of aqueous methanol solutions having equal freezing points, when the freezing points are between 0’ and -15’ C. If the freezing points are below -15’ C. (+5’ F.), then the boiling points of ethanol solutions are higher than those of methanol solutions which have the same freezing points. R. J. KEPFER CHEMICAL DEPARTMENT DU PONTAMMONIA CORP. WILMINGTON, DEL. June 11, 1931
..............
Editor of Industrial and Engineering Chemistry: Mr. Kepfer is correct in stating “that the boiling points of aqueous ethanol solutions are lower than those of aqueous methanol solutions having equal freezing points, when the freezing points are between 0’ and -15’ C.” The original statement t o which exception has been taken was intended to refer to solutions of such concentration as are normally used in antifreeze mixtures, and hence reference was not made to solutions having freezing points above -15’ C. ELIZABETH W. ALDRICH BUREAU OF STANDARDS WASRINGTON, D. C. July 7, 1931
Heat Transmission to Water Flowing in Pipes Editor of Industrial and Engineering Chemistry: A. E. Lawrence and T. K. Sherwood [IND.ENG.CHEM.,23,301 (1931) J state that the power of cz/& was found t o be 0.5. Our exhaustive research checks this value exactly. There is an indication that the power of c z / & gradually diminishes as the value of this modulus increases. It is possible that the value 0.37 which has been observed by many investigators is merely a result of a n average. Lawrence and Sherwood state that tube length has only a very slight effect on f ilm coefficients. Their conclusion may be correct in their particular tube sheet assembly for a single-pass tube. However, in a commercial multi-pass exchanger, there is d turbulence factor expressed by McAdams and Frost as (1 50/r), and substantiated by our research, which clearly indicates that film coefficients inside tubes vary inversely as a power of the tube length. No mention was made as to the type of solder used in their thermocouple junctions. We have encountered difficulty with copper-constantan thermocouples with soldered junctions a t temperatures above 175” F. (79.44’ C.). Any solder containing lead, zinc, and tin alloys undergoes a change in state a t about 185”F. (85’ C.) or higher, which would make the use of solder in this case questionable. We wish to agree with these investigators in that there is no discrepancy between the heating and cooling coefficients such as reported by Stanton, and Morris and Whitman. Our research involved an exhaustive series of tests covering steam to oils, oil t o oil, water to oils, steam to water, water to water, steam to air, and water to air. L. J. COULTHURST L. P. SCOVILLB
+
Freezing and Boiling Points of the Ternary System EthanolMethanol- Wa ter
FREEZING POINT
Vol. 23, No. 8
SOUTHWESTERN ENCINEERIKG CORPORATION 4800 SANTAFE AVE. Los ANGELES, CALIF. June 2 2 , 1931 ..............
c.
91.1 87.8 86.0 84.8 etc.
Editor of Industrial and Engineering Chemistry: The comments of Coulthurst and Scoville substantiating the use of the exponent of 0.5 on the c s / k group are indeed gratifying.
