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THE CHEMICAL WORLD THIS WEEK Carbon composition resistors of one watt capacity that gave a reproducibility from run to run of about ztO.1% were found most suitable for use as thermometers in low temperature calorimetry by Ellsworth H. Quinnell of the Naval Research Labo ratory. Such resistors are manufactured by the Allen-Bradley Co., he said. They produce a sensitivity of about 1009fc at liquid helium temperatures. A semiempirical relation between resistance and temperature is of the form: log R -fK/log R = A + B/T, where R is resist ance, Τ is temperature in degrees Kelvin, and K, A, and Β are arbitrary constants. Values of R at room temperature ranged from 10 to 270 ohms. With a bridge ca pable of measuring one part in 5000, tem perature changes smaller than 0.01° at 2 ° K. can be detected, since the resistance increases as the temperature is lowered. Application of these thermometers to heat capacity studies of normal and supercon ducting indium were described. The need for more and better calibra tion standards was pointed up b y Charles E. Messer of Tufts College who reviewed the need for such secondary standards and the criteria for their selection. He recom mended that a series of high purity or ganic liquids be made available whose freezing points would be spaced at tem perature intervals of 15° to 25° over the range from 90° t o 300° K. Dr. Messer presented data o n some 40 compounds and discussed the relative merits of each with regard to their use as standards.
Those attending the conference were told that measurements on synthetic sap phire have been made and are ready for publication. Synthetic sapphire, along with η-heptane and benzoic acid, were selected as standards for the intercomparison of precision heat capacity calorimeters and samples of the substances are being dis tributed by the National Bureau of Stand ards. NBS is also preparing the standards and evaluating the data obtained from them. These standards will be issued without charge to any reputable laboratory agree ing to report the results of their measure ments in full to the bureau. Requests should be sent to G. T. Furukawa, National Bureau of Standards, Washington 25,
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The conference discussed the proposal of the Division of Physical and Inorganic Chemistry
of the
AMERICAN
CHEMICAL
SOCIETY that the Calorimetry Conference operate within the framework of the divi sion. The group decided to abide b y the decision of a committee appointed b y the chairman. Edgar F. Westrum, Jr., Uni versity of Michigan, Edward J. Prosen, National Bureau of Standards, and Guy Waddington, Bureau of Mines, were ap pointed to consider the question. The group also elected Daniel R. Stull of Dow Chemical to continue as chairman and Guy Waddington as vice chairman. EDITOBS* NOTE: W é are pleased to acknowledge the assistance of Daniel R. Stull in providing the information on which this report was based.
Synthetic Polymers Provide Models of Body Compounds C&EN REPORTS:
Symposium on Polyelectrolytes
BROOKLYN.—Physical chemists are beginning to suspect that some of the long chain compounds they have been synthesizing in their recently initiated studies of the polyelectrolytes behave in some way like the high molecular weight compounds in the human body. If they can succeed i n defining these analogies they hope that the synthetic polyelectrolytes will afford a physical model o n which they can study the intricacies of body chemistry. On Sept. 29 a group of specialists in this field gathered at the Polytechnic Institute of Brooklyn to discuss the possibilities of this extension of their studies. The study of long chain molecules having multiple ionized groups is a fairly recent development. As is the case in any new field the pioneers must borrow from older investigations. J. G. Kirkwood of Yale came to the meeting to describe his established technique for the separation of large molecules by electrophoresis convection in the hope that the method could be applied to the polyelectrolyte compounds. The audience seemed to think CHEMICAL
that it might be possible and suggested that even in cases when the differences in rates of migration were not sufficient to achieve adequate resolution it might be possible to complex the electrolyte with some other group which would enhance its convection rate. Getting down to the primary subject under discussion, Aaron Katchalsky of the Weizmann Institute of Hehovoth, Israel, slipped a new and firmer theoretical foundation under the entire study of the large, multiply charged molecules. He reported a successful method of calculating the Helmholtz equation to obtain the free energy of such polymer systems and also their electrostatic field energy. Fortunately for his predecessors these new calculations confirmed the empirical formulas that have been used in the past. However, they now make it possible to determine something about the shape of the molecules under different conditions, at least the distance between the ends of the chain, which in turn gives an indication of their viscosity. Perhaps even AND ENGINEERING
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THE CHEMICAL WORLD THIS WEEK
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4172
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more important, the new formulas inake it possible to determine the activity co efficients of multicharged molecules s o that the interactions between two such mole cules can be understood quantitatively. These new calculations also explain the mechano-chemical systems responsible for the properties of t h e "synthetic muscle" which Katchalsky introduced at the recent World Chemical Conclave. Ephraim Katchalsky, the other half of the brother-team at the Weizmann Insti tute, set out directly to find out what he could learn about t h e physiological activ ity of the polyelectrolytes, by introducing various polypeptides into body enzyme systems. He reported that, unlike most biological reactions, those involving the polyelectrolytes were nonspecific. The multicharged molecules would combine with bacteria, tissue compounds, or t h e en zymes themselves. The molecular weight of the polymers seemed to have an impor tant bearing on the direction in which they would react but there are apparently other undetermined factors which effect the equi librium system involved. It was the basic polypeptides that reacted with bacteria. In concentrations as l o w as 10 g a m m a per milliliter they precipitated the bacteria out of the body fluid and destroyed their ability to reproduce. In slightly higher concentra tions the polymers decomposed the bac teria completely. Katchalsky cautiously mentioned the possibility that this phen omenon could lead to a new type of anti biotic but reminded his audience that the long chain compounds will also react with many other body chemicals. The reactions between the synthetic polyelectrolytes and the proteins may afford a simple and effective way of frac tionating these body components accord ing to Herbert Morawetz of Brooklyn Poly. Because of their high concentration o f ionizable groups, he said, they should replace the proteins from t h e saltlike complexes i n which they normally occur and permit separations of proteins which w o u l d nor mally react with each other. H e reported a study of the complexing of serum-al bumin with polyvinyl amine and polymethacrylic acid which indicated that such fractionation could be accomplished. No denaturing of t h e protein was observed and the polyclectrolyte-protein complex was simply decomposed by precipitating the polymers with specific counter-ions. In closing the sessions, which were generally conceded to have been highly productive, Aaron Katchalsky expressed t h e hope that ihe physical chemists had been able to provide the biochemists with a n e w tool in the polyelectrolytes. H e said that he had observed that physiological chem istry seems to have stagnated because i t has reached the limits of advance possible with the classical, empirical techniques o f investigation. A n e w surge of advances i n this field is just beginning to get under way, he predicted, as the result of the i n troduction of theoretical techniques of t h e physical chemist into biological sciences.
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