2888
Vol. 67
ADDITIONS AND CORRECTIONS 1960, Volume 64 George T. Armstrong and Sidney Marantz: The Heat of Combustion of Diryanoacetylene. Page 1778. W. H. Evans and R. H. Boyd have called to our attention the fact that in Table I, the correction, p3,for unburned - AET') were applied with the carbon, and the term wrong sign. A typographiral error also occurred in the sign of the correction, 94. The correction p3 was calculated from the mass discrepancy m. - na,' on the basis that the discrepancy represented unburned carbon remaining in t'he bomb. When properly applied, this correction increases the scatter of the experimental values significantly and creates a linear dependence on m a - m9'. The alternative is to assume that unburned C4Szescaped from the bomb, collected along with GO? in the absorber, and decomposed there to carbon under the influence of light. On this basis the heat value would be affected only by the energy of vaporization of the unburned CaN2. The mass of C*XSactually burned, mb, can be determined in this instance from t'he mass discrepancy by the relationship nib = m s - 1.375(rn, - ms'). I t is evident from traces of C found in the bomb that a combination of minor processes affected the heat value obtained. The validity of the judgment that the principal minor process is that of decomposition of unburned material outside the bomb is attested by an addkional fact,. One experiment, previously mentioned, having a mass discrepancy of 653, that was discarded because of a black deposit in the COSabsorber, now gives a result within 0.270 of the mean of the experiments, XT-hereas all other processes suggest,ed lead to a large disagreement of this experiment. The revised portions of Table I are listed below as Table IA. The correction q5 is for vaporization of unburned in the amount calculated as indicated above.
TABLE IA CORRECTED COMBUSTION DATAFOR REACTION 1 -91, -95, -A~T", -AHznso, - 93, Sample
j.
-
J.
j.
kj.
kj. mole-'
2074.7 2072.0 2077.8 2075.2 2078.2 2075.6 2076.5 2073.9 2078.7 2076.1 -0.7 Alean 2074.6 3~0.7 Standard deviation of the mean Data derived from the mean AHzsgo in Table IA are (in kcal. mole-'): AH2ga0 (combustion of liquid), -495.5 f 0.2; AHm8' (I), 119.6; AHizoso(g),126.5; binding energy, GEORGE T. A4RMSTROSG.
1 1 2 2 2
15.4 8.6 10.4 9.4 5.6
-0.2 -0.8 -0.4 -1.8
1961, Volume 65 Bojan Hamlin Jennings and Suzanne N. Townsend: The Sonochemical Reactions of Carbon Tetrachloride and Chloroform in Aqueous Suspension in an Inert Atmosphere. Page 1574. Use of an erroneous extinction coefficient for the calculat,ion of H202concentrations resnlted in incorrect rate constants lor peroxide production (Table 11). These should react d(H,Oz)/dt = 1.2 X 10-1 pmole/min. a t 20" and 1.6 X IO-' pmole/min. a t 3j0. At both temperatures the initial rates over the first 10 min. were slower than the ultimate linear rates, in agreement. with the results of Parke and Taylor (J. Chem. Soc., 4442 (1%6)).-BOJAN HAMLIN JENNINGS. 1962, Volume 66 J. M. Haynes: Use of Krpptoii for Surface $ r w ,Iluusurement s. Page 185. In column 1, line 40,30 cni. should read 30 mm.-J. M. HAYSES. Richard P. Wendt: Studies of Isothermal Diffusion a t 25" in the Svst,ernWater-Sodium Sulfale-Sulfuric Acid and Tests of the Onsager Relation. Page 1283. Table I, in line 11 for expt. 5 , 7399 should read 73.99; in line 7 for expt. 12, 1.1516 should read 1.15816.
Page 1284. Table 11,in line 16, VS should read v2. Column 2, lines 40-42: Values for the derivatives were found by using eq. mki =
...
(28)
8, ref. 34, and the . . . . . should read: Values for the derivatives mki =
.. .
were found by using eq. 8, ref. 34, and the . , . . Page 1285. Column 1,line 3, log (?& should read log (-,&*. Column 2, first'line after eq. 46, (nzl - 0.3 ) 6 ?fi (?E1 0.3) should read (a, - 0.3) 6 ml 6 (a 0.3). Page 1286. Table T:, in line 5 for expt. 11, 1.02281 should read 1.02218. ) read (Dll)v. Page 1287. Table VI, in line 4, ( D I I V should Page 1288. Footnote 49, ( L o )should read (L)~.-RIcHARD P.
y (DI~)".(DsI)~.-RICH~~RD P. K'ENDT. George Ndmethy and Harold A. Scheraga: The Structure of Water and Hydrophobic Bonding in Proteins. 111. The Thermodynamic Properties of Hydrophobic Bonds in Proteins. Page 1773. In our discussion [G. Nbmethy and H. A. Scheraga, J. Phys. Chetn., 66, 1773 (1962)l of hydrophobic bonding in polypeptide pleated sheets (section 4b), distances between CY- and pcarbons of the side chains were based on the atomic coordinates published by Pauling and Corey in their first paper [L. Pauling and R. B. Corey, Proc. Natl. Acad. Xci. U . S., 37, 729 (1951)l discussing these structures. It was brought to our attention by Prof. J. T. Edsall that,, in a later paper [L. Pauling and R. B. Corey, Proc. Satl. Acad. Sci. U.S., 39,253 (1953)], revised atomic coordina,tes and repeat distances were given, corresponding to structures nit,h st'raight hydrogen bonds. On the basis of these dat,a, the at'omic distances differ from the values given in our paper. The corrected values are as follovrs: AZo3g the chain direction, similarly oriented grogps are located 7.00 A. apart in the antiparallel chain and 6.50 A. apart in the given earlier for parallel chain pleated sheets, instead of 6.68 both structures. The change is small a.nd thus does not affect our earlier conclusions, stating that there is a single layer of water molecules between subsequent side chains. Perpendicularly to the chain a,xis, the dist>ancesbetween the a-carbons alternate between 4,; and 5.4 -I., those betmen the 8-carbons between 4 . 3 and 5 . 2 A. in the case of the antiparallel chain pleated sheet. The 4.1 and 4.3 1.separations allow a strong hydrophobic bond to be formed; The new dishnces correspond even more closely t,o the 4.0 A. "contact distance" calculated with the aid of van der Waals radii [L. Pauling, "The Kature of the Chemical Bond," 3rd Ed., Cornel1 University Press, Ithacn, X. \-., 1960, p. XiO]. -4s compared with the results in the original article, the van der Waals interactions between the CY-carbons n o r turn out to be somewhat weaker, t,hose between the p-carbons sornexyhat stronger, The two changes are approximately equal, leaving the E R contribution in APE+'' and hehce our estimate of -0.6 kcal./mole for the free energy of formation of the bond unaffected. Interactions between the y- (and 6-) carbon atoms of longer side chains are not altered. Irr thc parallel chain pleated sheet, the wrrected pcrpcriclit.ulnr 5 (t.oi~ip:trwito ttic: earlier valuo cif 1.73 rcpcitt distance is 4 . ~ l. The change corresponds to LL very s~riallweakening of the van der Waals interactions betveen the CH2 groups, with an estimated change of but 0.02 kcal./mole in ER. This change does not affect our previous estimate of A F H ~ 'for this case in a significant n i a n n e r . - H a ~ o ~A. ~ ScacRA0.4.
s.,
4
Irwin H. Billick : Velocity SedimentmationStudies on Pressure a.nd ConcentIrationDependent, Syst,ems.
