122nd NATIONAL ACS MEETING
Glenn T . Seaborg, University of California a n d c h a i r m a n of the Division of Physical and Inorganic Chemistry, discusses param a g n e t i c resonance with speaker B. Bleaney of C l a r e n d o n L a b o ratory, Oxford, E n g l a n d
Arthur W . Davidson ( l e f t ) , University of Kansas, a n d Jacob Kleinberg ( r i g h t ) , University of K a n s a s a n d c h a i r m a n of t h e Symposium on Liquid Ammonia C h e m i s t r y , discuss their p a p e r with Clifford G a r d n e r of U C L A
DIVISION OF PHYSICAL AND tNORGANIC CHEMISTRY
See Large Scale Production Of Pure Rare Earths • Key to solution of structure determination problems seen in application of magnetic resonance techniques • Thermochemical d a t a and studies of oxidation states aid progress in liquid ammonia chemistry • Shock waves present interesting new technique in studying kinetics of fast reactions • Corrosion preventative seen in application of theory of irreversible thermodynamics to electrochemical systems 4 VAILABILITY of large quantities of the *** rare earths in high purity was easily one of the most exciting prospects presented before the sessions of the Division oi Physical and Inorganic Chemistry. Hardly less promising are t h e advances along b r o a d fronts of chemical knowledge toreseen when chemists and chemical engineers become more familiar with the theory and techniques being explored in t h e new fields of nuclear and paramagnetic resonance, liquid ammonia chemistry, kinetics oi very last reactions, and electrode processes. Kach of these topics was the basis oi one-day symposia in addition to a full program of general papers. F u r t h e r engineering and process develo p m e n t will be followed by expansion to an industrial scale which will make all of t h e individual rare earths available in considerable quantities, stated Boyd \ \ V u \ e r 4136
of Oak Ridge National Laboratories, in his description of progress m a d e in achieving satisfactory liquid-liquid extraction of the rare earths. But recently declassified, the work on liquid-liquid extraction promises to open u p a whole new field of chemical research. The prospect of having large quantities ( kilogram amounts have already been p r e p a r e d ) of relatively pure rare earths to work with leads to broad speculation as to what the future might bring. W a r r e n C. Johnson of the University ol Chicago, chairman of the session at which the papers were presented, said that new metals and new compounds which may have wholly unexpected properties may be iound when chemists are able to get theii h a n d s on really ample amounts of the previously rare lanthanides. D. F. Peppard of Argonnc National Laboratory, who originally suggested the C H E M I C A L
method of using tri-n-butyl orthophosphate as an organic extractant with nitric or hydrochloric acid for the separation of the lanthanides, described a countercurrent, multiple extraction unit with multiple scrubbing by which t h e lanthanides can b e divided into two groups, t h e split occurring at any predetermined point d e pending upon t h e process variables. W i t h another division any individual rare earth may b e isolated from all other lanthanides. U n d e r t h e conditions of their current work, Dr. P e p p a r d ' s group, which includes J. P. Paris, P. R. Gray, a n d G. W . Mason, h a v e o b t a i n e d separation factors of b e t w e e n 1.5 and 2. In the kilogram-scale experiments at Oak Ridge, w o r k has been d o n e with single extractions, pseudo-countercurrent batch systems, and continuous countercurrent columns by a group w h i c h includes in addition to D r . Weaver, F. A. Kappelm a n n , J. A. Goggin, F . B. T h o m a s , F . M. Scheitlin, R. L . Bailey, and A. C. T o p p . Factors which h a v e been studied include acid concentration, rare earth concentration, nitrate concentration, t e m p e r a t u r e , dilution of the organic solvent, and t h e effect of one element on another. Separation factors as high as 7 b e t w e e n neodymium and s a m a r i u m have b e e n realized. From kilograms of concentrate containing about SiY/r gadolinium the major part of this element has been segregated into portions which h a v e a gadolinium content above 9(Y/c. Separation of dysprosium from yttrium h a s been found feasible. N a t u r a l N e p t u n i u m . F u r t h e r evidence for t h e existence in nature of t h e 4n -f- 1 series first postulated by Seaborg in 1947 was presented in another p a p e r by Dr. Peppard w h e r e i n he announced the isolation of approximately 10"8 microgram of neptunium-237 from the processing of a Belgian C o n g o pitchblende concentrate. 1 Working with Dr. Peppard on the project were G. W . Mason, P. R. Gray, and J. P. Mech, all of Argonne. T h e thorium-229 content of a large sample of thorium-230 AND
ENGINEERING
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PHYSICAL AND INORGANIC CHEMISTRY obtained from t h e concentrate waste w a s determined by isolating t h e actinium-225 daughter. T h e uranium-233 to uranium238 ratio was t h u s found to b e ( 1 . 3 i t 0.2) χ ΙΟ"13. Therefore, he a d d e d , t h e maximum n e p t u n i u m - 2 3 7 to uranium-238 ratio is ( 1 . 8 dt 0.4) χ 10"12, t o b e com p a r e d with the plutoruum-239 t o uranium238 ratio of ( 1 . 5 ± 0.2) X 10 » in t h e same deposit. H e estimates t h a t t h e true value is p r o b a b l y m u c h smaller than this maximum. T h e thorium-229 t o thorium232 ratio was f o u n d t o be less than 3 X 10~14 in a Brazilian monazite as compared with 4 X 10~ u i n the pitchblende sample. H y d r a z i n e · Commercial preparation of hydrazine b y an electric discharge t h r o u g h ammonia gas w a s predicted in a paper by W . Hoyt Andersen, B . J. Zwolinski, a n d R. B. Parlin of the University of Utah. A high frequency rather than a d.c. dis charge is employed to reduce t h e r m a l effects to a m i n i m u m since t h e stability of hydrazine is temperature d e p e n d e n t . It was found t h a t high How rates of gas through t h e d i s c h a r g e tube, small dis charge currents, low pressures, and small electrode g a p distances are most effective for producing highest hydrazine yields p e r unit of energy dissipated in t h e discharge tube. T h e m a x i m u m yields under t h e conditions employed were from four to six grams of h y d r a z i n e produced p e r kilo watt-hour of energy dissipated in t h e dis charge t u b e . Better results could b e o b tained to some extent if all conditions were at an optimum. M e r c a p t a l b u m i n S t r u c t u r e . Measure ments of t h e dielectric constant of h u m a n serum m e r c a p t a l b u m i n monomer have been found in general agreement with t h e previously proposed molecular weight a n d configuration of t h e protein by J. L. Oncley and associates a t Harvard. Using 69,000 is the molecular weight of t h e monomer, Dr. Oncley calculated from t h e measure ment that 700 D e b e y e units is the value of the dipole m o m e n t . T h e dielectric dis persion curve o b t a i n e d from t h e measure ments is entirely consistent with t h e cal culated curve for a n ellipsoid molecule with an axial ratio of four, molecular volume of 60,000, a n d angle of the dipole moment with t h e major axis about 3 0 ° . Dr. Oncley feels that this appears t o b e a satisfactory m o d e l for the monomer a n d ngrccs with other estimates of its size a n d idiape. F u r t h e r work with the mercury chiner, however, suggests t h a t models other than ellipsoids of revolution may have to be •onsidered. Using similar measurements or the dimer, Dr. Oncley and his co workers found t h e dipole moment to he ibout 1000 D e b e y e units, a value not particularly compatible with t h e symmetry L'xpeeted if a rigid charge distribution is iissumed. Relaxation times appear to be of the proper o r d e r of magnitude, b u t t h e dispersion curve is rather complex a n d floes not seem t o be explained with only (wo relaxation times. Complex Ion Formation. Kntmpy (liange in complex ion formation is deter
VOLUME
mined b y two general factors, propose Wendell M. L.ttimter and William L. Jolly or t h e University o f California a t Berkeley. These t w o factors are the entropy change involved in r e p l a c i n g a water molecule hound to> the a q u e o u s ion by t h e complexing ion o r molecule and the effect upon the surrounding xvater of changing t h e charge o n the ion. T h e y measured t h e heats of the six successive reactions of fluoride ion with the aluminum ion t.o form anion AlF« (III ) complex ion. W i t h these values and t h e equilibrium c o n s t a n t s the authors were able to calculate the entropy change i n each stejp. T h e v a l u e s were: 3 2 , 26, 1 8 , 13.5, a n d -3 calories per degree. These entropy c h a n g e s for t h e six reactions were analyzed in terms of the two g e n e r a l fac tors t h e y proposed. T o check t h e validity of their theory, t h e principles w e r e applied to t h e entropies o f formation of the cviprammonuum, silver ammonium and t w o silver cHloride complexes. Experimental values were f o u n d to be in general agree ment. Acid Dissociation. Applications of physical chemistry methods to g e t quanti tative results o f t h e degrees of dissociation of strongs acids in glacial acetic acid were used by Thor 1^. S m i t h and John H. Elliot of Hercules P o w d e r . Eleven s t r o n g acids were studied u s i n g α-naphtholbenzein a n d 0-nitroaniline. Ac-cording to t h e i r results, acid strengths increased in t h e following order: hydrochloric, methanesulfonic, sul furic, sulfoacetic, chlorornethane sulfonic, chlorosulfoacetic, riydrobromic, perchloric, methionic·, chlororncthionic, a n d methane trisulfonie. Dissociation constants f o r perchloric a n d hydrochloric acids were found t o he 9 >< 1 0 7 and 5 X 10 ,f>,
A skclcFi of the 11-atom ring structure p r o p o s e d by M a u r i c e L. Iluggins of Kodak HesearcH Laboratories for t h e helix of the a l p h a forms o f t h e synthetic polypep tides a n d fibrous proteins. T h i s cliiÎers s o m e w h a t from t h e structure proposed b y Pauling and C o r e y , in which they postulate a 13-ntom ring structure respectively, Dissociation constants from previously p u b l i s h e d conductivity d a t a were calculated. Values of t h e change in dissociation construit for monobasic acids in anhydrous solutions were calculated from lb» and found to be in moderate
3 0, N O . 4 0 » » O C T O B E R
6, 1 9 5 2
agreement with values obtained from conductivity data. T h e authors interpret t h e conductivity and indicator data as demonstrating that equilibria in acetic acid involve undissociated species primarily.
• Magnetic Resonance Techniques The idea that nucleii, electrons, and other particles of matter can b e exactly located in a chemical structure was explored at the Symposium on Nuclear a n d Paramagnetic Resonance. T h e phenomenon ol nuclear and paramagnetic resonance is still relatively n e w a n d t h e chairman of t h e symposium, II. S. Gutowsky of the University of Illinois, organized his program t o give a broad picture of t h e many interesting possibilities offered through the use of magnetic resonance. Because of t h e recent development of t h e field and the few chemical laboratories which have published work, early speakers outlined t h e fundamentals and principles involved. Nuclear and paramagnetic resonance were defined as two types of spectroscopy, at radio to microwave frequencies, in which transitions a r e observed between energy levels established b y an external magnetic field interacting respectively with nuclear magnetic moments, oi with t h e magnetic moment of an unpaired electron or electrons, usually in bulk samples. In pure quadrupole spectroscopy transitions are induced b e t w e e n energy levels established by the interaction between a nuclear electric quadrupole moment and some electric field gradient, usually associated with t h e electron distribution in a chemical bond. The interrelation of these phenomena is extensive, since t h e nuclear magnetic moments can interact among themselves οτ with t h e magnetic fields associated with t h e electrons, a n d the interaction of a nu clear quadrupole moment with an electro static field gradient modifies t h e interac tion of its magnetic moment with an ap plied magnetic field. These effects show u p as a splitting of the absorption lines, a broadening, a narrowing, or a change in intensities. Many of the phenomena can b e observed as fine structure or hyperfine structure in optical spectra. The nuclear magnetic resonances de pend upon internuclcar distances and the nuclear motions, so are useful in structure determinations, explained Ε. Μ. Purcell. H a r v a r d University in opening the sym posium. In his own work he has found t h e coexistence of two solid phases of hy drogen at temperatures just below the melting point of hydrogen. In t h e work of L. II. Meyer and Dr Gutowsky at the University of Illinois on chemical shifts a n d electron distribution in molecules they found correlations between chemical shifts in the fluorine a n d proton resonances in organic compounds and other properties related to electronic structure. I n substituted fluorobenzenes, compari sons of the fluorine chemicals shifts with the» Ilamnu'tt sigma constants yielded
4137
122nd N A T I O N A L ACS MEETING separate linear relationships for the meta and para suhstituents. This result demon strates t h e difference in the relative im portance of the inductive and resonance mechanisms at the meta and para posi tions. T h e chemical shifts in multisubstituted ffuorobenzenes were found to be in close agreement to the sum of the values for the individual suhstituents. Quadrupole Spectra. Quadrupole spec tra give the electric field gradients in chemical bonds a n d are of value in es tablishing the nature of the bond hybridi zation a n d the extent of the ionic char acter, reported 13. P. Dai ley, Columbia University, in a paper on the chemical significance of quadrupole spectra. In a paper on the quadrupole spectra of molec ular crystals. Harry C. Allen, Harvard University, reported indications that chlo rine quadrupole constants in substituted chlorobenzenes are related to the electronic effects of the substituent, lie also found a correlation of the coupling constants with Hammett's sigma constants. Ralph Liv ingston, Oak Ridge National Laboratory, also reported data on quadrupole cou plings for a number of covalently bonded chlorine compounds. Paramagnetic Resonance. Two leading workers in the field of paramagnetic res onance outlined some of their work and plans in concluding the one-day session. S. I. Weissman, Washington University, St. Louis, predicted the usefulness of the phenomenon in t h e study and counting of free radicals. In bis work he has observed a hyperfine structure at high dilutions which depends on; magnetic properties of the* nucleii in the radical with which the electron is most intimately associated. B. Bleaney of Oxford England utilizes t h e hyperfine structure of nuclear proper ties to obtain information on the magnetic moment of the nucleus and the electron wave function (shell level). He has found also that the broadening of t h e nuclear magnetic resonance line indicates some thing about the internuclcar distances in volved. ί» L i q u i d A m m o n i a C h e m i s t r y Difficult handling problems and the problems of working in a closed system have slowed efforts of workers in the field of liquid ammonia in developing the many interesting facets offered by an ammonia system. At the Symposium on Liquid Am monia Chemistry, progress that would fur ther aid in learning more about reactions in a -.medium which is a poorer oxidizing agent than water was reported. Jacob Kleinberg of the University of Kansas pre sided at the one-day session. Oxidation States. The existence of oxi dation states incapable of existence in water was discussed in three papers. George \V. W a t t of the University of Texas gave data for potentiometric titra tions involving aluminum ( I f l ) iodide which show three distinct "end points," corresponding to one, two, and three elec tron changes. Me tentatively interprets 4138
these data as evidence for t h e existence in liquid Ν Ma of aluminum in the plus 2 and plus 1 oxidation states. Other interpreta tions have not been excluded. Recent work at the University of Kansas by Arthur YV. Davidson and Dr. Klein berg on the reduction of K 3 M n ( C N ) 0 and K ;i Cr(C\)« by potassium was described by Dr. Davidson. The reduction of t h e former compound results in the formation of a substance containing *both unipositive and zerovalent manganese, K.-.Mn( CN ) e .KoMn( CNT ),..2NM. Evidence has also been obtained which indicates that K : i C r ( C N ) e is reduced to a compound containing uni positive chromium. Thermodynamics. T h e preparation of the thermodynamic data needed in t h e preparation of n e w eompojmds in liquid ammonia is a project of Lowell V. Coulter, Boston University, who reported on the thermochemistry of the alkali and alka line earth metals and their salts in M L Dr. Coulter indicated that the state of the electron in moderately dilute solutions of the alkali and alkaline earth metals is the same. Me cited the larger heats of solu tion of halides of the alkali and alkaline earth metals in ammonia as compared with water as evidence for a greater solvation energy of ions in ammonia than in aqueous solutions. "Nascent Hydrogen." T h e concept of "nascent hydrogen" formed in certain aqueous systems may have foundation in physical fact, stated Richard A. Ogg, Jr., in a paper describing the mechanism of amide formation in metal-ammonia solu tions. Me proposed the following mecha nism: ( 1 ) electron -f NIL, - > NII"2 -f II ( 2 ) 2M + M - > II, + M M = N i b predominantly. Nascent hydrogen is simply atomic hydro gen formed according to t h e reaction: electron (from dissolved metal) —-> N I L
+ Π Measurement
of
Unpaired
Electrons.
The direct observation of the unpaired electrons in alkali metal solutions of liquid ammonia was reported by Clyde A. Hutchison, Jr., University of Chicago, through the use of a paramagnetic res onance absorption. In his experiments. Dr. Hutchison uses a low field strength and imposes a radio frequency on t h e sample perpendicular to the static field of the in strument. The resonance phenomenon is peculiar to the unpaired electrons and thus the unpaired electrons can be observed or counted without regard for the diamagnctism of the various molecular species present in the solution. • High Temperatures From Shock W a v e s Two different approaches to the study of fast reactions were presented at the Symposium on Kinetics of Very Fast Reac tions. The newer approach is the one in which a large burst of energy, is applied for a short turn to a mixture of gases that C H E M I C A L
An electron photograph of polyvinyl toluene latexes of extremely uniform par ticle size was shown with the paper by T. Alfrey, E . B. Bradford, and J. W . Vanderhoff of Dow and Gerald Oster of Brooklyn Poly. W h e n these latex par ticles dry slowly they arrange themselves in a long-range, close-packed crystalline array. They believe that study of this process will yield some u n d e r s t a n d i n g of the crystalline processes in metals do not react under normal conditions. T h e other approach, perhaps t h e more classical one, is the technique of mixing reactive chemicals very rapidly and then using fast observational techniques to determine what happens. T h e first approach was represented by three papers, two of which heated the sys t e m rapidly with shock waxes and the other with intense light. O n e method pro duced highly supersonic shock waves travelling at about the speed of 17 times t h e speed of sound and was accompanied by temperatures of 18,000° K. or more. This method, developed by Arthur Kantrowitz of Cornell University, utilizes high pressure hydrogen a n d low pressure argon. T h e high pressure gas is fed into one end (if a strong metal t u b e until the pressure build-up fractures a thin metal diaphragm and the hydrogen rushes with a great force into the low pressure argon on the other side of the diaphragm. T h e resulting release of energy produces the supers/Hiie shock wave a n d high tempera ture, which ionizes t h e gases. Intense light is emitted by the ionized gases and this light can be used to measure the degree of ionization. Dr. Kantrowitz has discovered a mechanism for the direct transfer of the energy of the gas in motion to the thermal energy of the electrons. T h e mechanism, he said, explains the high electronic tem perature associated with the shock front and he feels that it may account for the light and conductivity observed. The method of bursting a diaphragm between two regions of gas at different pressures was also used by Tucker Carrington and Norman Davidson of CalTech in a study of the rate of dissociation of N\C),. Temperatures (from —20° to 28° A.) and pressures (from 0.5 to four atmos pheres) used were much more normal than those used in Dr. Kantrowitz's project T h e reaction takes place in about 10 milAND
ENGINEERING
NEWS
POLYMER lionths of a second and is perhaps the fastest reaction rate ever to be measured directly. D r . Davidson feels that t h e use fulness of shock waves may ultimately be of applied as well as theoretical interest. T h e o t h e r rapid heating technique, em ploying a high electrical energy discharge through a flash l a m p , was discussed by D . A. Ramsay of t h e Canadian National Research Council. His apparatus consists of a gas tube one meter long and a photoflash tube of the s a m e length placed paral lel to the gas t u b e . T h e flash lasts about 0.001 second a n d releases about 4000 joules of electrical energy. (A continu ously operating l a m p of equal light inten sity would consume electrical energy at t h e rate of about 4 million watts.) A 2 1 foot absorption spectrograph is set to b e gin operation within one millisecond after t h e flash. T h e large light energy creates large instantaneous concentrations of free radicals a n d other dissociation fragments of molecules. Discussing the results of a hydrazine run through his apparatus, Dr. Ramsay said his observations suggest that t h e primary "step in the photolysis is dis sociation of hydrazine into hydrogen and N-H.t, followed b y decomposition of the latter product into N I L and NIL T h r e e other papers discussed the tech n i q u e of mixing chdmicals very rapidly a n d using fast techniques to observe the reaction. O n e of these papers, b y Martin Kilpatrick and associates from t h e Illinois Institute of Technology, measured both pressure changes a n d ignition rapidly. Ap plying their improved apparatus to t h e re action of sodium-potassium alloy with water, Dr. Kilpatrick found that the pres e n c e of oxygen delays ignition. Spectrometric techniques have b e e n de vised b y Bryce Crawford, Jr., G. R. Cowan, A. R. D o w n i e , M. C. Magoon, a n d D . L. Rotenberg of the University of Minnesota, and R. A. Ogg, Jr., of Stanford for observ ing moderately fast gas phase reactions. T h e i r infrared spectrometer is c a p a b l e of scanning any desired portion of the spec t r u m of a reacting mixture as frequently as 12 times a second. This instrument has been applied to several interactions of t h e oxides of nitrogen. Another study of the fast reactions of nitrogen compounds was reported by Har old S. Johnson, Louis Foering, and R. J. T h o m p s o n of Stanford. Using nitric acid vapor heated to 4 0 0 ° F . b y mixing with preheated nitrogen, tliey measured color changes rapidly as t h e gas reacted. Their findings suggest t h a t decomposition of ni tric acid vapor is more complex and faster t h a n previously proposed.
CHEMISTRY
D a v i d M . G a r d n e r ( l e f t ) , a n d John M. F i n n , Jr. ( r i g h t ) , at present with H o r i z o n s , Inc., o p e r a t e system for the study of p h o s p h i d e chemistry in liquid a m m o n i a at the Uni versity of Pennsylvania application in corrosion prevention. A det rimental reaction, h e said, could perhaps b e stopped b y maintaining another reac tion at constant electrochemical affinity. Insisting o n the necessity of using ir reversible thermodynamics in establish m e n t of logical a n d coherent presentation of electrochemistry, Dr. Van Rysscl b e r g h e said that irreversible phenomena a p p e a r in electrochemical systems as soon as current, however small, passes through t h e m . Irreversible thermodynamics can be applied to electrochemical systems not only to the range of validity of linear relations b e t w e e n currents and overvoltages, he said. However, in that range, he finds the
most immediate connections with experi mental studies. T h e manipulation which w o u l d find ap plication in corrosion prevention, no-cord ing to t h e speaker, is that of k e e p i n g an electrochemical affinity constant by main taining electrode potential a n d a m o u n t s ol reactants and p r o d u c t s of one reaction constant. The system could by this means he m a d e to evolve toward a state in which the velocity of another reaction ΛΛΌΠΚΙ come to a standstill. D r . Van Ryssclberghe is now complet ing a monograph on this topic and others in t h e field of irreversible electrochemical thermodynamics.
DIVISION OF POLYMER CHEMISTRY
Polymerization Rates Speeded Up For Chlorotrifluoroethylene • Second stage cross linking examined by com plementary procedures of copolymer synthesis and d e g radation • Condensation polymers enjoy resurgence oF interest at fundamental level
• Thermodynamic Theory
• "Popcorn" polymerization emerges mystery status as possible tool in polymer synthesis
Newly developed thermodynamics of ir reversible reactions as applied to electrode p h e n o m e n a were discussed by Pierre Van Ryssclberghe of t h e University of Oregon before the Symposium on Electrode Proc esses. Dr. Van Ryssclberghe suggested that this highly theoretical field may have
npKNTATivE limits on the degree of mono·*· mer purity necessary for production of acceptable ehlorotrilltioroethylene poly mer were reported by j . M. Hamilton of D u Pont at the Symposium on Chlorotriiluoroethylrne. This symposium (joint with Division of Industrial and engineer
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3 Ο,
Ν Ο.
4 0 . .
OCTOBER
6,
1952
From
ing Chemistry) was o n e of lour symposium and five general sessions sponsored l>y Un voting Division of Polymer Chemistry, interest in which is already rivalling that in some of the Society's older and larger divisions. Development of a rapid test-polymer— 41 3Ρ
