Explosions Key to Equilibria Detonation waves m a y provide experimental methods to study nucleation rates of solid particles HOUSTON.—It n o w appears that velocities of detonation waves provide t h e most accurate tool for determining thermodynamic equilibria at high temperatures. "Measurements agree with calculations t o better than * .>% accuracy," says Harvard's G. B. Kistiakowsky, "and I know of no other experimental method where absolute temperatures in t h e range of 3000° to 6000° K. can be determined for gases within a corresponding error of 1 % . " Detailed studies of lean acetyleneoxygen mixtures confirm this conclusion, he says, because the reaction products are well established—velocity calculations involve n o uncertain parameters. Other work with hydrogenoxygen and carbon monoxide-oxygen mixtures, while not as accurate, is also consistent with the assumption of complete thermodynamic equilibrium being obtained in the detonation waves. Thus the p a t h is clearly open for study of other high temperature equilibrium in gaseous systems, Kistiakowsky said at t h e Hydrocarbon Symposium sponsored by the ACS Southeastern Texas Section. Harvard scientists have been searching for situations where equilibrium may not b e attained because of special conditions generally defined in the Kirkwood-Wood theory. They now have clear evidence that this is the case when one of t h e reactions involved is delayed by an induction period. Rates of Nucleation. Complete equilibrium i n acetylene-rich oxygen mixtures requires precipitation of some solid carbon, Kistiakowsky explains. On the other hand, detonation velocities are determined by homogeneous reaction of oxygen with acetylene—excess of t h e latter remains as such a n d is supersaturated with respect to solid carbon. This condition exists w h e n the mixtures contain less t h a n 7 0 % acetylene. At 70% acetylene concentrations, discontinuous velocity changes occur somewhere along t h e t u b e in which t h e detonation wave propagates. According to Kistiakowsky, t h e initial wave corresponds t o the homogeneous reaction only, t h e superseding a n d faster wave to complete equilibrium, including solid carbon. H e frankly admits that the theory of this sudden change is n o t yet complete, b u t in this reaction it appears likely t h a t a device is available for investigating nucleation rates of solid particles from a gas. High S p e e d Reactions. T h e speed with which chemical reactions take VOLUME
3 3,
NO.
7
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place in a detonation wave after initial shock compression has been investig a t e d repeatedly. Pressure in t h e initial shock wave must be higher than t h a t calculated thermodynamically for the ChapmanJ o u g u e t state of complete reactions, h e emphasizes. Although claims have b e e n m a d e that the reaction zone has b e e n observed, Kistiakowsky believes they were erroneous because longer durations were attributed to these reactions than should be. Recent techniques, he asserts, have b e e n developed to a point where it is possible to study detonations in gases at initial pressures as low as 20 m m . Using stoichiometric hydrogen-oxygen mixtures with a slight addition of xenon to enhance x-ray absorption, reaction zones have now been observed at initial pressures below 0.1 atmosphere. Surprisingly enough, t h e reaction rate in these mixtures appears to vary as t h e s q u a r e of t h e initial pressure, a n d if this relation continues up to one atmosphere initial pressure, t h e reaction zone must last only b u t 10~ s second. Reactions are substantially completed after only 10 3 molecular collisions, h e indicates, a rather amazing speed, a n d one which is h u n d r e d s of times faster than in ordinary flame reactions. Although shock and detonation wave studies h a v e been in progress only a few years, Kistiakowsky says there is every reason to believe t h a t m u c h furt h e r information of interest will b e obt a i n e d in t h e future. H e indicates that investigations may b e further expanded w h e n the theory of spinning detonations, which a r e nonstationary b u t r a t h e r periodic phenomena, is advanced to t h e point where they also can b e used as a research tool. Methyl Affinities. Experimental methods h a v e been developed for d e termining the relative addition rates of m e t h y l radicals t o aromatic compounds, according to Michael Szwarc, State University of N e w York. T h e relative addition rates (called methyl affinities) h a v e been determined for the series of aromatic hydrocarbons like benzene, diphenyl, naphthalene, phenanthrene, chrysene, pyrene, stilbene, benzanthracene, anthracene, and naphthacene. Other studies include some heterocyclic compounds like pyridine, quinoline, isoquinoline, and acridine; various aromatic derivatives like ethers, ketones, a n d nitrocarbons; a series of quinones; a n d various vinyl monomers. Szwarc finds that a linear relation exists between t h e log methyl affinities
FEBRUARY
14,
1955
Less t h a n
0.007% Ashf o r Highest Accuracy left: Platinum crucibU, with 2 0 gr. S&S A*h« Free Filter Paper below: Crucible after completed incineration
Ask f o r S&S "Ash-Free" A n a l y t i c a l Filter Papers For many years S&S Ash-Free Analytical Filter Papers have been known for their extremely low ash content. They have been the choice of chemists w h o must have the most precise working tools. To our knowledge, there is no filter paper with lower ash content on the market. In fact, ash content of S&S Quantitative Papers is considerably lower than all other papers we have tested—less than 0.007%, Ask your laboratory supply house for S&S Analytical Filter Papers—the finest, most precise filter paper you can specify. Yet S&S quality costs no more. If you would like to receive a free S&S Filter Paper Sampler, made up of many grades, just mail the coupon below. MAIL THIS COUPON FOR FREE SAMPLER Bjg Œ B IBB —ffT 0ΒΒ B B BBS BBS BBB Bl
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RESEARCH and the log relative addition rates of CC1 8 radicals to aromatic hydrocarbons. H e is proposing to consider the slope of this straight line as a measure of the ratio of intrinsic reactivities of methyl and trichloromethyl radicals. There is a monotonie relation be tween methyl affinities a n d the tripletsinglet energy transitions, he says, and this relation has been explained in terms of a n energy diagram—the con clusion has been verified experimentallv.
• Terramycin h a s b e e n t a g g e d with carbon-14, making it t h e first b r o a d range antibiotic to b e tagged, accord ing to Pfizer Therapeutic Institute. J. F . Snell, Richard Wagner, and F r a n k A. Hochstein fed radioactive material to Streptomyces rimosus; carbon-14 was absorbed first by the organism and then by t h e molecule it produces. Ra dioactive Terramycin—which will b e available to medical researchers in six months—will enable study of t h e chemi cal action of Terramycin in living tissue.
cording to Lederle Labs, initial clinical investigations indicate that in some cases it shows fewer undesirable side effects than other folic acid antagonists such as aminopterin. ^Tobacco Industry Research Commit tee increases to $ 1 million its fund for research into tobacco use and health. The committee m a d e an initial alloca tion of $500,000 last year, of which over $300,000 h a s already been set aside for specific grants. ί S t a n f o r d Research Institute obtains an additional 2000-curie source of ra dioactivity from Brookhaven National Lab. It doubles SRI's source of co-
balt-60 and makes it possible for ex periments in cold sterilization of food a n d the effects of radiation on materials a n d chemical reactions to be carried out in half the time previously re quired. • O r i g i n s of life on e a r t h will b e studied at Queen's University, King ston, Ont., with a $20,000-grant from Carnegie Corp. J. R. Vallentyne will study organic compounds present in pre-Cambrian rocks. T h r o u g h tests for presence of amino acids, h e has ob tained proof that rocks of minimum age of 1.4 billion years contain surprisingly high amounts of organic matter. Such analysis may provide scientific evidence
National Science Foundation M a k e s 120 G r a n t s National Science Foundation has m a d e 120 grants totaling about $1.6 million for support of basic research in the natural sciences, for conferences and studies on science, for scientific information exchange, for t h e scientific manpower register, and for travel of American scientists to international scientific meetings. This is the second group of awards m a d e during fiscal year 1955 (C&EN, Nov. 29, 1954, page 4 7 5 6 ) . Among grants are: Contract
Investigator
Hrigham Young University Mechanism of Adsorption of Ions by Silicate Minerals • Concentrated intrinsic factor has University of California Thermodynamic a n d Magnetic Properties of been prepared by Lederle L a b s ' Wil Matter at Low Temperatures University liam L. Williams, L. Ellenbogen, a n d Cornell L,3 Shift in Molecular Rearrangements Ray Esposito. One or 2 mg. of t h e Harvard, University Unstable Intermediates in Gas Reactions Lederle substance now constitutes a University of Illinois Transference Numbers of Salts in Nonaqueous therapeutic dose, instead of the 5 0 m g . Solvents formerly used. Starting with a partial Iowa State College Primary Products of Thermal Decomposition purification of intrinsic factor from a n Reactions in Solution Johns Hopkins University ammonium sulfate-precipitated frac Synthetic Studies on Chlorophyll tion, they purified it further by diges Mellon Institute Relative Energies of Polar a n d Equatorial tion with enzymes, chilling, centrifugDerivatives of Cyclohexane Northwestern University ing, filtration, alcohol fractionation, and Molecular Potential Energies ultrafiltration, they say in current issue University of Pittsburgh Chemiluminescence of Photosensitizing Organic of Ρ roc. Soc. Exptl. Biol. Med. Elimi Dyes in Condensed Systems of Rochester nation of impurities will facilitate study University Kinetics and Mechanism of Thermal Reactions of structure and function of intrinsic Smith College Synthetic and Structural Investigations in the factor. The material may eventually Sesquiterpene Series of Washington b e used to treat pernicious anemia p a University Mechanisms of Oxidation Reactions W a y n e University tients. Alpha-Amyrin Chemistry of Wisconsin • The Giauque-Kelvin Proposal to d e University Synthesis of Alkaloids University of Chicago fine the absolute scale of t e m p e r a t u r e Thermodynamic Study of Minerals on the basis of a single fixed point has D a r t m o u t h College Systematic Compositional Variation in Metabeen a d o p t e d b y t h e International morphic Minerals Texas A. & M. Research Foundation Committee on Weights and Measures Calcium Carbonate Solubility Equilibrium in and t h e General Conference on Sea Water Institute of Technology Weights and Measures. T h e t w o Carnegie Transfer of Matter Across Gas-Liquid Inter faces groups selected for this point t h e Georgia Institute of Technology triple point of water and assigned it Protein Changes with Chlorine State College the value of 273.16° K. American Kansas Effect of Sonic Vibration on Rates of Mass scientists were recommending 273.17° NforthTransfer Carolina State College K. (C&EN, April 26, 1954, p a g e 1 6 6 8 ) . Mechanism of Biochemical Oxidation of Or ganic Matter Action b y t h e two groups completes California Institute of Technology X-Ray Diffraction Studies of Crystalline action on t h e proposal and p u t s t h e Proteins n e w definition into use. Configurations of Polypeptide Chains in Proteins University of Illinois Carbohydrate Absorption: Synthesis a n d Deg radation of Polysaccharides • A folic acid a n t a g o n i s t called Pennsylvania State University 10 Methotrexate ( 4 - a m i n o - N - m e t h y l Nucleic and Desoxynucleic Acid Fragments of California pteroylglutamic acid) is b e i n g mar "University Hypothalamic Regulation of Pituitary Function
keted for treatment of leukemia.
600
Ac
C H E M I C A L
Amount S 5,100
Goates, J . Rex G i a u q u e , W.
30,000
F.
M e i n w a l d , Jerrold
11,000
Kistiakowsky, G. B.
25,400 3,400
R a y , B. Roger H a m m o n d , George S.
12,900
C o r w i n , Alsoph H.
13,900 6,200
Miller, Foil A.
10,000
Frost, Arthur A. Rosenberg, Jerome
L.
W a l t e r s , Winston D . S offer, Milton D .
10,700 16,000 9,000
W i b e r g , Kenneth B.
17,000
D j e r a s s i , Carl
16,000
V a n T a m e l e n , Eugene E . Ramberg, Hans Lyons, J. B.
9,000 27,000 7,200
W o o d , Donald W.
20,000
Toor, H e r b e r t L.
13,500
Irigols, Robert S. F£all, R a y m o n d C. N e m e r o w , Nelson L .
7,100 12,000 7,000
C o r e y , Robert B.
36,000
P a u l i n g , Linus
30,000
L a m e r , Joseph
16,000
Pepin sky, R a y
20,000
R o b e r t s , Sidney
24,000
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