VOL. 30, NO. 7
INDUSTRIAL AND ENGINEERING CHEMISTRY
a42
results is of interest, even thodgh the provitamin of milk is not ergosterol. The great difference (a factor of about 5 x 106) between the results of Haman and Steenbock and those of the present writers is not surprising when we remember that only a small part of the electrical input to a carbon arc gppears as ultraviolet radiation of wave length less than 3100 A., and, further, that a large part of the absorption of such wave lengths by milk is due to substances (chiefly protein) other than the provitamin.
Acknowledgment The experimental portion of this work was supported by the Cherry-Burrell Corporation. The writers are indebted
to Loomis Burrell and to C. B. Dalzell of that organization for their generous cooperation. They are also indebted to the Wisconsin Alumni Research Foundation with whose support the compilation of results was made possible.
Literature Cited
,
(1) Haman, R. W., and Steenbock, Harry, IND.ENG.CHEM.,Anal. Ed., 8, 291 (1936). (2) O’Brien, Brian, and Morgareidge, Kenneth, Proc. SOC.Ezptl. Bzol. Med., 32, 113 (1934). REC~IVE March D 24, 1938. This paper is an extension of material reported under the same title before the 31st Annual Meeting of the American 6ooiety of Biological Chemists, Memphis, Tenn., April 21 to 24, 1837.
CORRESPONDENCE Thermodynamics in Hydrocarbon Research SIR:In a recent paper Thomas, Egloff, and Morrell ( 4 ) referred to some of my earlier work (1,d ) in which thermodynamic data are applied to the problems of cracking and hydrogenation. Explaining in detail the limitations and deficiencies inherent in any thermodynamic treatment of such a problem which is truly kinetic in nature, I stated ( 2 )that not thermodynamic considerations but the principles of reaction kinetics are of prime importance for the actual procedure of these reactions; the latter are in no way connected with the energy content as calculated from thermodynamic data. Moreover, in another paper (3) I explained: “It should be clearly understood that thermodynamic caIculations may be applied only with care to problems of this type, since reaction rates primarily depend upon the energy of activation which is not related to the thermodynamic probability of some equilibrium between the initial and the final state of the system. Thermodynamics, therefore, affords a decision only about the possibility but not about the actual occurrence or the course of some definite chemical reaction.” It is my desire to stress the viewpoint taken by Egloff and his associates, particularly since their quotation of my results suggests that there must have been some possibility of misinterpretation, although I hoped that my opinion was made perfectly clear in my earlier publications. GEORQR. SCHULTZE PHYSICAL-CEEMICAL INSTITUTE UNIVIURSITY OF BERLIN, GERMANY December, 1937
..... SIR: From Schultze’s publications it is apparent that he fully realizes the limitations of the thermodynamic method. According to our interpretation, Schultze does not always stay within these limitations. For example, he discusses (1) the general cracking equation:
+
C m + nHz(m+ .)+z = C ~ H Z ~ +Cn’L Z
+
His conclusions are quoted: “Of all the ( m n - 2) different decomposition possibilities that comply with the equation, that reaction is most probable for which the resulting olefin is as large
+
as possible (i. e., n = m n - 1). This explains the formation of methane as the predominant constituent of the gas from
cracking.” We do not believe that such a conclusion can be reached and justified on the basis of thermodynamics alone. CHARLES L. THOMAS GUETAV ECLOFF J. C. MORRELL UNIVERSAL OIL PRODUCTS COMPANY CHICAQO ILL. Deoembir 23, 1937
Literature Cited (1) Schultze, Angew.*Chcm., 49,268, 284 (1936). (2) Schultze, Oel,Kohle. Erdoel, Teer, 12,267 (1936). (3) SchultEe, 2. Elektrochem., 42,674 (1936). (4) Thomas, Egloff, and Morrell, IND.ENQ.CHW 29, 1260 (1837).
Correction Our attention has been called to several errors in our recent paper on “Thermodynamics in Hydrocarbon Research” [IND. ENG.CHEM.,29,1260 (1937)l: METHANE(page 1261). AHoZo8should read -18,070 instead of +18,070. ETHANE(page 1261). A H O mshould read -20,600 rather than -2060. WPENTANE (page 1262). AHoag8 for the liquid should read -42,230 instead of -2570. ISOPENTANE (page 1262). The first sentence should reed: ANozss = -38,080 for gaseous and S O 1 9 8 = 69.5 for liquid ieropentane, instead of A H ” Z S= ~ -38,080 and S0m = 59.5 for liquid isopentane. ~-HEPTENE (page 1263). AF0zsa ehould read 20,720 instead of 8920. IBOBUTENE (page 1265). A F ’ m should read 14,240 instead of 14,290. In all these cases the figures are correct in the original Table 11, so that the values given there are unchanged. CHARLES L. THOMAS GUSTAV EGLOFF J. C. MORRELL
