INDUSTRIAL AND ENGINEER.lNG CHEMISTRY
1258
country, Professor Dennis may be regarded as a true “citizen of the world,” who “knows his Europe” as do few Americans. He has crossed the Atlantic many times, and has in the aggregate spent many months in touring various parts of England and the continent. In his numerous avocational interests Professor Dennis has displayed energy and skill of an order comparable with that shown in his professional work. As a young man he excelled in baseball, tennis, and boxing, and sang second bass in his college glee club. His remote Scotch ancestry may be in part responsible for his later proficiency in golf, his keen business insight, and his canniness as a purchaser of laboratory equipment and supplies, and perhaps even for his dignified disapproval of Volsteadism. He is one of the most skilful local players of pool, billards, and bridge.
Vol. 22, No. 11
A fitting climax to the long series of constructive achievements that marks the career of Professor Dennis is afforded by his conspicuously successful work in planning the magnificent Baker Laboratory of Chemistry a t Cornell. His was the master mind chiefly responsible for the intricate design of this edifice, in which have been incorporated the ideas and ideals accumulated by him over a period of more than half a lifetime of observation and study in America and Europe of the principles of laboratory design and administration. The Baker Laboratory stands as a monument t o the constructive genius and executive ability of Louis Munroe Dennis. To but few men has been vouchsafed a memorial so lasting and so truly characterizing their life work as this! A . W. BROWNE
NOTES AND CORRESPONDENCE Vapor Pressure and Heat of Vaporization
Carbon Black in Rubber Insulating Compounds
Editor of Industrial and Engineering Chemistry: I n a paper by Nutting which appears on page 771 of the July AND ENGINEERING CHEMISTRY, the equation issue of INDUSTRIAL L = A ( T , - T)” is put forward as new. I t has, however, previously been suggested by Thiesen, Verhandl. deut. Physik. Ges., 16, 80 (1897) ; Kendall, Medd. Vetenskapsakad. Nobelinst., 2, No. 29 (1912), No. 36 (1913); Hemptinne, Bull. sci. mad. TOY. Belg., [5] 12, 296 (1926); and Winter, J . Phys. Chem., 32, 576 (1928). The use of a factor which vanishes for T = T , is common to many empirical latent-heat formulas; L , of course, vanishes a t the critical point. The fact that L varies slowly with T can be reproduced by taking a fractional power of the factor. With regard to similar surface-tension formulas to which Nutting refers, it has been shown by Sugden, J . Chem. Soc., 125, 32 (1924), that for a number of non-associated liquids the classical van der Waals expression for the variation of surface tension with temperature may be written y = K ( l - T/T,)’.* = KI(T, - T)’.2 T. S. WHEELER ( K ,K1 are constants).
Editor of Industrial and Engineering Chemistry: In an article under the above title by W. B. Wiegand and C. R. Boggs, which appeared in the August issue of INDUSTRIAL AND ENGINEERING CHEMISTRY, the statement is made: “carbon black may be incorporated in a dielectric such as rubber without detracting from its insulating or dielectric properties. Published results to the contrary were in error, probably because the material was added in excessive amounts.” The “published results” were those of the authors of this note [Bur. Standards, Tech. Paper 299, 713, 720, 721, 7221. I4 I3
12 II IO
9
6 WALNUTAVE.
HARTFORD, CHESHIRE,ENGLAND August 28, 1930
Editor of Industrial and Engineering Chemistry: It appears t h a t a relation between heat of vaporization and temperature, given as new near the close of my paper on vapor pressure, has already reached a respectable middle age and the dignity of repeated discovery. I am indebted to Professor James Kendall and to Mr. Wheeler for calling my attention to the fact. It is indeed surprising that a relation so simple, so logical, and so useful should not have found a place in our standard reference texts of thermodynamics and of physical chemistry. Both surface tension and heat of vaporization are obviously simple functions of energy of association and therefore of the temperature measured downward from the critical temperature. Numerical data fit this formula very closely over a wide range of temperatures. Still it finds no place in texts devoting pages t o outworn and empirical relationships. P. G. NUTTING U. S. GEOLOGICAL SURVEY D. C. WASHINGTON, September 27, 1930
c
8
3 7 a g6 u
g 5 I-
24 A W
E 3 2
Figure 1-Effect
of Carbon C o n t e n t on t h e Dielectric Constant of Rubber
We wish to point out that our results are not contrary to those of Wiegand and Boggs. When both sets of results are plotted on the same scale, as is done in Figures 1 , 2 , and 3, they show substantially the same effect of carbon black on the electrical properties. The only discrepancy is that their results show a small lowering of the power factor with certain proportions of carbon, which our published results do not show. This agreement is
INDUSTRIAL AND ELVGINEERINGCHEMISTRY
November, 1930
1259
for other uses, notably for telephone, telegraph, and submarine cable insulation, carbon black is detrimental in any proportion, because it increases the dielectric constant. We are familiar with no electrical use of rubber for which the addition of carbon black would result in striking or even important improvement. I n making this statement we refer to actual uses, and not to the requirements of certain specification tests. With some compounds the addition of small amounts of carbon black may sufficiently increase either the resistivity or the dielectric strength, or both, to permit these compounds to meet a particular specification, but the amount of increase is not sufficient to improve appreciably the service which can be obtained from such compounds. We have published no data on the dielectric strength of rubber because we are not a t all sure that it is a significant property of the material, however useful it may be as a test for rubber products. H. L. CURTIS A . T. MCPHERSON BUREAUOF S T . 4 s D A R D S WASHTNGTOS, D. C. August 15, 1930
..............
0
2 t 6 VOLUME PER CENT CARBON
Figure 2-Effect
8
IO
12
of Carbon C o n t e n t o n t h e Power Factor of Rubber
surprisingly good, especially when one considers that there is no strictly logical basis for comparing the two sets of results, because Wiegand and Boggs replaced various proportions of whiting with carbon black in highly compounded stocks, whereas we added carbon black to a pure gum base compound. Since our results do notzdiffer materially in character from those of Wiegand and Boggs, the contrast between our published statements about the effect of carbon black and their claims of striking improvements in electrical properties resulting from its use must arise from the manner in which the electrical measurements are interpreted. We consider t h a t statements about improving the electrical characteristics of rubber can properly be made only with reference to specific properties and specific uses, because various types of insulation require very different electrical properties. For some electrical uses of rubber, the addition of small percentages of carbon black may not be detrimental, provided the electrical characteristics as measured on anhydrous test samples are retained by the rubber under service conditions. However,
Editor of Industrial and Engineering Chemistry: We beg to reply as follows to the communication of Curtis and McPherson: “We wish to point out that our results are not contrary to those of Wiegand and Boggs.” (1) Dielectric Strength. In our paper i t was shown that this property could be increased by as much as 40 per cent. I n Tech. Paper 299 no data whatever on dielectric strength are given. To the statement of Curtis and McPherson that they are “not a t all sure that it is a significant property of the material, however useful it may be as a test for rubber products,” we reply that the data of our paper do relate, not t o pure rubber, but to rubber compounds typical of present-day wire technology. (2) Power Factor. In our paper a n improvement in power factor amounting, in the case of the 40 per cent compound taken a t 1000 cycles, to 48 per cent (nearly half) was observed. Curtis and hlcPherson admit that their published results show no improvement. ( 3 ) Resistivity. In our paper an improvement reaching 68 per cent was noted in the case of a 40 per cent rubber compound, 42 per cent in the case of a 30 per cent compound, etc. Curtis and McPherson in Figure 17, page 713 of Tech. Paper 299, show a continuous drop in resistivity with the addition of carbon black. In their letter they have, however, drawn a new and entirely different curve. In this revised curve there is shown a small increase. Inspection of the curve and the text on page 713 makes i t obvious that in their original treatment of the data on the effect of carbon black they completely overlooked the improvement due to small additions, evidently attributing the higher resistivity a t about 2 per cent carbon black to experimental error. Only when redrawing their curve in the light of the authors’ treatment of the effect do they bring out the phenomenon under discussion. “However, for other uses, notably for telephone, telegraph, and submarine cable insulation, carbon black is detrimental in any proportion, because it increases the dielectric constant.”
+
2 6 8 IO 12 VOLUME PER CENT CARBON Figure 3-Effect of Carbon C o n t e n t o n the Resistivity of Rubber
0
To this we reply that our data, as also those of Curtis and McPherson, clearly indicate t h a t for the percentages of carbon black required to improve breakdown, resistivity, and power factor the dielectric constant is raised only very slightly. Thus with the 40 per cent rubber compound the average increase in dielectric constant for d. c., for 1000 cycles, and for 440,000 cycles, was 10.5 per cent; for the 30 per cent compound the average increase was 7.8 per cent; and for the 35 per cent compound con-
1260
INDUSTRIAL AiZ’D ENGINEERING CHEMISTRY
taining reclaimed rubber the increase was 2 per cent. This adverse change in dielectric constant is slight compared with the improvement obtained in the other electrical properties so that the net effect should be beneficial. Not all submarine cable is telephone and telegraph cable, and even then we believe experimental evidence would be required to prove the sweeping statement of Curtis and McPherson that carbon black in any proportion is detrimental. Naturally in any specific application intelligence should be used in considering which properties are controlling. In conclusion, we believe that the experiments described in Tech. Paper 299 were entirely correct, due allowance being made for the fact that the carbon black was not incorporated in a bonedry condition, as in the case of our experiments. The importance of this difference in method of application will be reported a t greater length in a forthcoming paper in which the effect of carbon black on insulating oils will be described. I n this paper data will be given which not only confirm and extend the conclusions reached in our paper on rubber compounds but throw additional light on the mechanism of the improvement. C. R . BOGGS W. B. U’IEGAND SIMPLEX WIRE & CABLECo., BOSTON, MASS. BIXNEY& S M I T H CO., N E W Y O R K , N. Y . October 3, 1930
New Books The George Fisher Baker Non-Resident Lectureship in Chemistry at Cornel1 University. I-Spatial Arrangements of Atomic Systems and Optical Activity. 11-Methods, Results and Problems of Precise Measurements at High Temperature. 111-The Constitution and Structure of Ultramarines. F. M. JAEGER. McGraw-Hill Book Co., Inc., New York, N. Y . 450 pp. Price, $4.00.
Vol. 22, No. 11
Cracking of Hydrocarbons at Temperatures Higher than Critical Temperatures Editor of Industrial and Engineering Chemistry: I n the September issue of INDUSTRIAL AND ENGINEERING CHEMISTRY Ralph H. McKee and Antoni Szayna have a valuable contribution on “Cracking of Hydrocarbons at Temperatures Higher than Critical Temperatures.” My theory of knocking in internal-combdstion engines, to the effect that “knocking is due to the thermal decomposition of the large fuel molecules into a number of smaller molecules with corresponding increase of local pressure,” is mentioned by the authors and they are of the opinion t h a t the results obtained by them are in disagreement with such a theory of knocking. I do not wish to go into a discussion of the merit or lack of merit of my theory, but I wish to submit that the valuable research work carried out by the above two authors has no bearing whatsoever on my theory. The decomposition of hydrocarbons to which I refer in my theory takes place a t the flame temperature of the internal-combustion engines, therefore appreciably above 2000” C., and is greatly influenced, even by slight variations of this temperature, as caused by admixture of exhaust gases, while the experiments of McKee and Szayna were conducted a t temperatures slightly over 400” C., a t which temperatures, as they state themselves in some cases, polymerization takes place, which is of course out of the question a t the flame temperature of the engine. EDWARD SOKAL AMERICAN KATALITE CORP. 312 WE5T 7 5 T H ST., NEWY O R K , N. Y . September 17, 1930
BOOK REVIEWS Life Expectancy of Physical Property Based on Mortality Laws. BY EDWINB. KURTZ. 205 pages. The Ronald Press, New York, 1930. Price, 16.00. The chemical plant executive and the chemical engineer frequently face the problem of establishing suitable bases for plant and equipment depreciation, and usually adopt arbitrary percentages formulated partly on experience and partly on expectancy of life. Mechanical engineers and operators of public utilities have had opportunities to develop experience standards, and while there is a greater degree of uniformity in the depreciation percentages used by such groups, it would seem to be due to the semi-standardization resulting from the tabulating and averaging of published figures rather than by reference to a mortality fact basis. The author deplores this situation and draws attention to the similarity of slope and curve amplitude between human mortality tables, based on world-wide life insurance data, and the few available equipment mortality tables. With a meager basis of actuarial data on equipment, the mathematical probabilities are explored and procedures developed for a variety of uses. I n his preface Professor Kurtz says, “It is confidently believed these basic findings will in time become the foundation stones on which theories and practices of depreciation will be erected as superstructures.” While the reviewer is not prepared to accept the author’s endorsement of his own views, the material gathered together and presented mathematically and graphically in the book does suggest that a more extensive collection of data on the life of mechanical equipment, when subjected to ordinary usage, should enable a more scientific determination to be made of depreciation percentages and obsolescence. Unfortunately most chemical plant equipment, like a combatant in war, is subject to a chance sudden end or extensive hos-
pitalization,” which no mortality curve can predict. When we have reached the zenith of our desires and attained the chemical engineers’ Philosophers’ Stone-complete corrosion resistancewe can begin to depart from “experience and expectancy” and develop our mortality tables. The chemical engineer concerned with appraisals, valuations, and determinations of depreciations will, despite the difficulties of applying Professor Kurtz’ methods to chemical equipment, find in this book much suggestive matter applicable to the depreciation factors of mechanical adjuncts of a chemical factory.A. E . MARSHALL Weld Design and Production with Particular Application to Safety and Cost. BY ROBERT E. KINKEAD. 108 pages. The Ronald Press, New York, 1930. Price, 14.00. This book is a very timely u arning to the users of welding and will no doubt be read with interest. The apparent simplicity of uniting metal parts by one of the many uelding processes naturally tends to its use, but welding like all other means available for mechanical production has its very peculiar inherent nature that cannot be trifled with if proper results are to be obtained. Mr. Kinkead has very ably presented what may be expected and why certain results are obtainable mith u-elding; and throughout the whole shows that only when proper technic is folloR ed can satisfactory results be obtained. Careful consideration by experienced engineers of the adoption of 4elding, then proper selection of materials with carefully prepared design, is absolutely necessary for success; and, as so well explained in this book, the selection of the most suitable welding equipment, the qualifying of the welders and the instructions as to volume of heat, time, and application, all part of procedure control, will all together produce uniform satisfactory results that always are the least costly.-E. H. EWERTZ
