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COMMUNICATIONS TO THE EDITOR
thiourea. Inhibition is prevented when zinc is added simultaneously with one of these agents. The present data constitute a further test of the hypothesis that pyridine nucleotide linked dehydrogenases may prove to be metalloenzymes.' The results here presented give impetus to continued exploration in this direction. Acknowledgments.-These studies were supported by grants-in-aid from the National Institutes of Health of the Department of Health, Education and Welfare and the Howard Hughes Medical Institute.
Vol. 78
there are ring phosphates even larger than the octametaphosphate. The total ring content in this partly hydrolyzed sample of Graham's salt is not large, being about 1Oyo of the total P. Most of the phosphate applied to the chromatogram has not moved from the origin (this allows overloading of the paper). IUORGANIC DIVISIONRESEARCH LABORATORY XIOXSAXTOCHEMICAL COMPANY J. R VAN LYAZER DAYTON 7, OHIO E. KARL-KROUPA RECEIVED I'EBRUARY 20, 1956
SELF-DIFFUSION IN MOLTEN SODIUM NITRATE' BIOPHYSICSRESEARCH LABORATORY DEPARTMENT OF MEDICINE BERTL. VALLEE Sir: HARVARD MEDICAL SCHOOL AND We have measured the self-diffusion coefficients PETERBENTBRIGHAM HOSPITAL BOSTON, MASSACHUSETTS WARREN E. C. WACKER~of both sodium ion and nitrate ion as a function of RECEIVED JANUARY 23, 1956 temperature in fused sodium nitrate. The method _ _ ___ OF THE
employed involved a determination of the rate a t which tracer sodium or nitrate ion diffused from a ca. 0.65 mm. i.d. quartz capillary tube into a EXISTENCE OF RING PHOSPHATES HIGHER THAN stirred bath of pure sodium nitrate. The method THE TETRAMETAPHOSPHATE was originally used by Anderson and SaddingtonP Sir : in aqueous solution and has since been employed We have shown recently that spots attributable by others, particularly W z ~ n g . ~Fairly detailed to pentametaphosphate and perhaps higher ring investigations have proved that the method is phosphate anions are obtained in the two-dimen- susceptible of good accuracy.3 ~ 4 Self -diff usion sional paper chromatography introduced by Ebel. coefficients of liquid sodium5 and mercury6 have These results are part of a study of the hydrolysis of been measured by the capillary method. The only Graham's salt which has been under way in our previous published work on self-diffusion in molten laboratories for about three and one-half years. salts appears to be that of Berne and K l e ~ n mwho ,~ A number of chromatograms have been made on obtained the self-diffusion coefficient of thallous a partially hydrolyzed sample of Graham's salt ion in molten thallous chloride; we know of no having a number average chain length of 117 prior work in which diffusion has been determined phosphorus atoms per molecule ion, as deterinined for both cation and anion. by end-group titration corrected for the presence of In our experiments radioactive N a Z 2 was the rings. Schleicher and Schuell paper No. 5S9, sodium tracer which was followed by standard Orange Ribbon, was employed, with over-loading counting techniques. The nitrate tracer was by the use of 45 pg. of total P in the drop placed labelled with stable OIs which was determined mass a t the origin instead of the optimum amount of spectrographically on the oxygen liberated when the 15 pg. which we have recommended elsewhere.2 nitrate was decomposed quantitatively to nitrite In the series of ring phosphates on the chromato- and oxygen. Some rather severe difficulties had to gram, there are separate and distinct spots for be overcome in filling and calibrating the capillaries trimetaphosphate, tetrametaphosphate, pentanieta- because of the ele\-ated temperatures. The ternphosphate, and perhaps hexametaphosphate.3 The peratures were controlled during diffusion t o 0. I spot attributed to hexametaphosphate partially to 0 . 2 O . overlaps a continuous band which we attribute to The self-diffusion coefficients, W, may be exunresolved higher ring phosphates. In this sample, pressed by rate equations of the form :U = '4 there is also a continuous, but less intense, band exp(-LH*/KT) where A is a constant, AII* which curves upward so as to form a continuum is the energy of activation for the diffusion, l< a t the high-molecular-weight end of the series of is the molar gas constant and T is absolute ternchain phosphates. Since the continuum attributed perature. The self-diffusion coeficient of the to higher chains and the continuum attributed to sodium ion in fused sodium nitrate betiyeen :31t5 higher rings branch apart so as to form a Y , we and 3'75" is given by feel that there is relatively good evidence for ring '(J\, = 12.85 x 10-4 exp(-437o/K1': cin.?,'bvv. phosphates containing as many as eight phoswhile that for the nitrate ion similarly is phorus atoms. Indeed, the appearance of the chromatogram would lead one to suspect that e x g ( - 5 0 8 3 / R T ' ) ctil.z,/svc. 9 0 4 0 ~ = 8.91 i< (9) Fellow of t h e National Foundation for Infantile Paralysis.
*
(1) J. P. Ebel, B d I . SOL.Chiin. Fvance, 2 0 , 991 (1953). ( 2 ) E Karl-Kroupa, A n a l . C h e m . , submitted for publication. ( 3 ) ? h e hexametaphosphate described here bears no relation t o t h e term "hexametaphosphate" which has been so often misused in both t h e technological a n d scientific literature as t h e name for vitreous sodium phosphates having NazO/P20a mole ratios lying between 1.0 and 1.2. T h e hexametaphosphate described herein is a single rnolecular species consisting o f a 12-membered ring of alternating ]'€io\pilorus and oxygen atoms; whereas t h e "herametaphosphate" o f clrmxnerce is a mixture uinsistinx pre
