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Nature of Matter Prologue to New Chemicals and Materials T H E transmutation of various elements in Rutherford’s laboratory, early in this century, with Einstein’s derivation of the equation E = mc2, established the equivalence of mass and energy. Thus, the first law of thermodynamics which expressed the conservation of energy was extended to include matter as a form of potential energy. This revolutionary generalization still left the kinetic question open, as to whether man could transform matter into energy by any workable scheme. The experiments of Hahn and Strassmann stimulated Meitner- and Bohr to propose fission, and the Manhattan Project with its fission bombs unambiguously established the kinetic as well as the thermodynamic practicability of trans. forming matter into energy.
Worlds and Antiworlds With sufficiently purified uranium235, a liberated neutron in turn liberates other neutrons. The resulting chain reaction permits the uranium-235 system to go critical and like the familiar chain reactions in conventional explosives, the system can be detonated. Fusion, by adding the hydrogen bomb, is another kinetic triumph, since the thermodynamic possibility of hydrogen transforming into helium with the liberation of energy follows from the packing fractions. At this level matter and energy are a single subject. A few more such general considerations are necessary. Experience in the form of the principle of detailed balance requires that every process in which matter is converted into energy can, under the appropriate conditions, be reversed. Thus, one naturally assumes that a t some time in the past matter condensed from energy. This immediately raises a variety of questions. First, why do we have our world of positive nuclei and negative electrons rather than the equally plausible antiworld with negative nuclei? This is analogous to the chemical question: Why are the proteins of living things built of I-amino acids instead of the equally usable mirror images, the damino acids? Apparently in the long evolutionary process the critical structures which first succeeded in initiating catalytic replication involved the 1amino acids, although the successful system might equally well have used the d-amino acids. When the I-amino world had once been initiated, its rapid development quickly outmoded the damino world and made its emergence
substantially impcssible. Analogously, it is possible to suppose that when the positive nucleus had emerged it acted catalytically to replicate itself and quicl ly the incompatible antiworld lost all possibility of successfully competing. However, if there is an antigravitational repulsion between matter and antimatter, the two kinds of particles would automatically separate into galaxies removed from each other. T h e fact that in pair production as observed with coincidence counters, equal amounts of matter and antimatter are always formed suggests that worlds and antiworlds may be equally abundant. The next 10 years should indicate whether, and if so where, these antiworlds are to be found. Parity raises an interesting problem. For some 25 years the nucleus was assumed to be free of potential energy terms that change sign when the nuclear coordinates are inverted in the origin. Thus the principle of parity denies the existence of potential energy terms for the nucleus such as kxyz. Such a term occurs in the potential function for an electron inside any molecule lacking a center of symmetry. An electron in such a field rotates the plane of polarization of light as Condon, Altar, and the author showed using quantum mechanics, although not in the classical approximation. When cobalt is placed in a magnetic field a t low temperatures, so that the nuclei are oriented as a result of their nuclear magnetic moments, the escaping electrons pass out along the nuclear south pole. This means the nucleus has a more complicated structure than was Freviously supposed and it raises the question where the cobalt nuclei corresponding to the opposite sign for k are to be found-Le., where are cobalt atoms which would emit @particles from their north pole? Again there is the possibility that cobalt nuclei are formed by a catalytic process from radiation or from elementary particles and that whichever catalyst chances to emerge first determines the type of cobalt atom subsequently created, or perhaps the anticobalt atom is the inverse ofthe atom we know. Within the next few years spontaneous generation a t the lowest level may be demonstrated. Thus the component molecules ‘ of ribonucleic acids and proteins a t high concentrations and under favorable conditions should spontaneously combine to form ribonucleic acid and enzymes with self-replication
of both types of molecules. Such an event would be heralded by a sudden change in optical rotation, with an increase in viscosity coming after an initial protracted induction period. The astronomical search is already on for evidence of antiworlds. If a n antiworld should collide with ordinary matter, the resulting annihilation of particles would emit radar signals proclaiming the occurrence. T h e next 10 years may bring the answers. The parity experiment with cobalt suggests that oriented cobalt atoms may replace gyroscopes in the guidance of bodies mobing in space. Once oriented, the cobalt nuclear magnets, like ordhary gyroscopes, disorient slowly, so that the emerging P-particles are emitted in a fixed direction in space independent of the spacial orientation of the vehicle carrying them; this direction can be established using a Geiger counter. I n spite of extreme experimental difficulties this should evenplace the usual types of gyroThe well developed molecular of the chemist reappear in the explanations of nuclei. In the nuclei resonating n-mesons hold the nucleonr together much as electrons bind the atoms in complex molecules. Everything points to a rapid improvement ih understanding of the forces inside the nucleus. The nature and number of the elementary particles will be clarified. Chemists should play a central part in this development. I n the early 1930’s Planck thought matter was compounded of neutrons, protons, and electrons. Photons were a fourth type. This list of elementary particle41 was expanded to about 30, but has now dropped to about 10. Ten years will clarifiy our understanding of the number and nature of the elementary particles. The Pauli exclusion principle is a n easily applied empirical rule which badly needs clarification. What influence is operating between two particle4 with like spin, which vanishes if the particles have unlike spins? The r antisymmetric wave funclike elementary particles, as n the exclusion principle, is good as long as it works.
logical Questions ics and tranquilizers are but two of a flood of new chemical contributions to biology. I n the next 10 years we can expect present tranquilizers to be plmost completely replaced by VOL. 51, NO. 1 e JANUARY 1959
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less toxic and more specific agents. Spectacular chemical aids to mental health will expand many times within the next decade. Atherosclerosis will probably be brought under control by using unsaturated plant fats such as linoleic acid and substances like sitosterol, which interfere with the adsorption of cholesterol and so prevent the yellow patches which clog our arteries. This will be only part of the advance in understanding cortesonelike substances and the other hormone effects of the sterols. The sterols seem to regulate the permeability of cell membranes in a highly specific and selective fashion. Insulin with its amino acid structure apparently regulates the passage of glucose from the blood into the cells. The diabetic, lacking insulin, is reduced to a general slowdown of his chemical plant, located in the cells, except as he receives supplemental supplies of insulin from outside. T h e mechanism by which each cell constituent passes in and out of the cell is receiving close attention. Cells customarilj have a n outside voltage 0.1 volt more positive than that inside. Presumably some metabolite, formed inside the cell, complexes with sodium ions to form a structure which passes readily through the cell membrane, whereas the component parts of this complex pass through with difficulty. If the metabolite is buffered outside the cell a t a low concentration-by reaction with ground substance, for example-a steady state is reached with high sodium concentration and high positive potential outside the cell. Potassium and other ions do not completely escape such pumping effects. Histamine, the decarboxylation product of histadine, is the type of physiologically active metabolite which might be tied u p by the acid groups attached to the extracellular ground substance and may be the pump substance for sodium in certain cells. Serotinin (5-hydroxytryptamine) is another possible pump substance. The critical nature of the pump substances in regulating ionic behavior in nerve impulses and in other cell activities makes identification likely in the near future. To cure cancer one must selectively inhibit the growth of the cancer cell, by denying it the constituents of chromosomes needed for rapid build-up of new cells or by interfering selectively with its use of glucose, which is the power supply of all cells. Two alternative reaction cycles break up glucose for use in all cells. The EmbdenMeyerhoff pathway predominates in normal cells: the hexose monophosphate pathway of glycolysis is more important in cancer cells. Thus inhibition of the latter pathway should selectively inhibit cancer cell growth. To do
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INDUSTRIAL AND ENGINEERING CHEMISTRY
this one should add antimetabolites of glucose-6-phosphate, 6-phosphog1uconic acid, or ribulose-5-phosphate. Of these only phosphogluconic acid is not used in the Meyerhoff-Embden reaction. Thus the step using 6-phosphogluconic acid is the logical one to block by addition of a n inactive analog which acts as a useless counterfeit. M. B. Sahasrabudhe (Nature, July 17. 1958) reports successful preliminary results in this classical attack on cancer. However, it is unlikely that selective inhibition of c m c r cell metabolism will be as effective LS counterfeiting essential constituents of the chromcsome through blocking cell growth with substances like 5-fluorsuracil. Other successful attacks on cancer will involve the subtle singling out of some vulnerable step in cell development with selective blocking of this step. The next decade will produce exciting substances to be used in treatment of the various types of cancer. The firefly and other kinds of luminescent systems have made cold light familiar. This occurs whenever in a reaction the reactants which start in the lowest state pass to a final state that is no longer the lowest. Much has been accomplished in understanding the oxidative enzymes in this and analogous oxidative reactions. T h e structure of the luciferin in the various systems is being established and many inhibitors are being classified as denaturants or as poisons. Flames ordinarily produce populations in the various excited states far out of equilibrium. The type of crossing of potential surfaces described for cold light is much more common among the higher levels in the high temperatures of flames. I t is not unusual for a Langmuir probe to reveal electron populations 107 times the equilibrium number expected at the observed temperature. Such excess concentrations can be understood as exotic new structures which have ionization potentials far below the usual 12 volts. Ions in flames will resemble structurally the ions found in solution with high temperature providing the ion stabilization which solvation provides in ionizing solutions. Within the next 10 years we should see improvements in high pressure equipment, so that $50,000 should buy a press which reaches 200,000 atm. at 2000' C. repeatedly with a cylindrical reaction cavity I j 4 inch in diameter by 3 inches long. Synthetic diamonds are now selling for $3.25 a carat, compared with an all-time low of $2.80 for natural diamonds, and because synthetic diamonds are about 35% more efficient in grinding they are successfully competing with the natural product. Within 10 years the synthetic diamond should drop to about 50 cents
per carat, by replacement of tungsten carbide in the press by something less prone to fracture. Gem diamonds will soon be synthesized. Because failure of tools and structural materials depends on dislocations and other imperfections, heating them and allowing them to cool while under high pressures, thus promoting the perfect lattice, will enormously improve hardness and strength. Similarly, certain high pressure phases will persist metastably a t room temperatures. Thus high pressure and high temperature treatmetlts should provide materials with a bewildering array of Froperties. Conductors, abrasives, semiconductors and substances with other unusual and important properties will be produced including materials with breaking strengths increased by orders of magnitude. Mineralogy and geology will change more and more into laboratory sciences. Further evidence should accumulate as to whether or not the extremely dense and conducting core of the earth is only a high pressure modification of the lighter materials abundant a t the surface. The choice of suitable materials to permit re-entry into the earth's atmosphere will be largely solved within the next 10 years. At room temperature the velocity of sound is almost 700 miles an hour. A satellite striking the atmosphere a t 30 times the velocity of sound would heat u p at the interface as though it were at 302 X 300 = 270,000° K. However, if the satellite is exposed to this heat only while it travels through SO miles of atmosphere a t 2000 miles an hour, this comes to about 3600 X S0/2100 = 9 seconds. Such a temperature is developed only in the layer of condensed gas which is pulled along by the satellite and is continually slipping away, carrying most of the heat generated with it. Nevertheless some of the heat reaches the nose cone by conduction, convection, and radiation. For short periods the nose cone can be thermostated a t almost any desired temperature by cooling it by vaporization of a n appropriate covering. By choosing a high polymer with a heat-resistant skeleton such as carbon and clothing the skeleton with atoms which will volatilize at the desired temperature, the nose cone can be protected as long as volatilization continues. Volatilization of a gas in this fashibn helps the satellite peel off its hot condensed gaseous envelope. I t is too early to guess what the best nose cone coating will finally contain, but the results already reported give assurance of ultimate success.
HENRY EYRING Department of Chemistry, University of Utah, Salt Lake City, Utah
