VOL 6, NO. 2
PHYSICAL C B ~ M I S ~SYMF~SIUU Y
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furnishes the only safe procedure in arriving at a correct theoretical equation of state for matter in any state of aggregation. Further familiar contributions of statistical mechanics may be cited. For example, the prediction of a chemical equilibrium in the absence of measurements on the equilibrium state itself requires a knowledge of the numerical values of the integration constant resulting from the integration of the Gibbs-Helmholtz equation. Classical thermodynamics is powerless to answer this question, yet statistical mechanics through the Sackur-Tetrode equation furnishes an exact answer to this problem as far as monatomic gases are concerned. In the case of polyatomic gases the results are not as clear cut, but sufficient progress has been made to get some very helpful results. If our knowledge of the equilibrium state is reaching a satisfactory condition, we unfortunately cannot say as much for the equally important problem of reaction velocity. We know the ratio of the two component velocity constants must equal the value of the equilibrium constant, but of the factors which contribute to the absolute value of the velocity of each component reaction we know very little. The methods of classical physical chemistry again seem to be powerless to unravel the mysteries of reaction velocity but if the present progress in atomic physics along the lines of predicting the frequency of the transitions in the subatomic energy levels continuesprocesses which are really nothing more than the simplest of chemical reactions-we ought to see much progress in the near future. Statistical mechanics makes the bold attempt to predict the behavior of the crowd on the basis of laws found valid for macroscopic bodies, and as such is a fundamental science which ought eventually to yield the key to the problem of reaction velocity.
Pht-Poisoning Compound in Walnut Tree Identified. Penta-hydroxy-alphanaphtha-quinone. That is the exact name, outlining for the understanding of organic chemists the exact structure of the stuff in walnut trees that keeps the ground under them bare of plant life. The tracing of this walnut poison t o its chemical lair was described recently before the physiological section of the Botanical Society of America by Everett P. Davis of the Virginia Agricultural Experiment Station. The antagonism of walnut trees t o other forms of plant life has long been noted by farmers as well as botanists. It was supposed that the trees poisoned the other plants, but nothing was really known of the nature of the substance until the Virginia researcher extracted and purified it. Having got the natural substance, he proceeded, after the manner of organic chemists, t o make a synthetic duplicate of it. This artificial product proved to he just as poisonous to plants as its natural prototype. Because the full descriptive chemical name is a bit cumbersome. Mr. Davis sought a shorter one far common use. The botanical name for the walnut is Juglans, so he called the newly discovered chemical "juglone."-Science Service
