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CRYSTAL STRUCTURE OF PERCHLORIC ACID MONOHYDRATE
by fumarase were made as described earlier23 using a Beckman DUR spectrophotometer with an expanded scale of 80 to 100% transinission. Additional measurements were made on a Cary 14 recording spectrophotometer with a 0-0.1, 0.1-0.2 absorbancy scale. Fumarase was isolated and crystallized by methods developed in t v s Laboratory.24 All kinetic data were obtained a t 25 & 0.2 Experiments were done a t pH 9.45-9.65 (& 0.05) in 0.001 ionic strength NaOH-glycine buffer and 80 and 120 p M malate. The ionic strength was varied by adding NaCl. The averaged initial velocities presented here are uncertain by approximately & 10%. Rough determinations of the Michaelis constant K M in 0.01 in ionic strength NaOH-glycine-NaCl buffer were made at p H 9.6-10.0 by use of Lineweaver-Burk plots. Electrophoresis experiments were made following pre-
.
(23) R. AI. Bock and R. A. Alberty, J . Am. Cliem. Soc., 76, 1921 (1953). (24) C. Brieden, R. AI, Bock and R . A. Alberty, ibid., 76, 2482 (1954).
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viously described procedures'Qin 0.001 ionic strength XaOHglycine buffer plus NaC1. Nitrogen was bubbled through the buffer solution during dialysis to prevent COZabsorption. In all cases, the conductivity of the buffer rather than that of the protein solution was measured. The fuinarase concentration was about 0.3 to 0.4 g./IOO ml. The pH was measured a t 0" using a line operated Leeds and Northrup pH meter. At p = 0.01, the field strength was about 2.1 volt em.-' and a t p = 0.1 about 2.9 volt em.-'. The heat dissipation was 0.0028 and 0.050 watt c1n.-3, respectively.
Acknowledgments.-The authors are extremely grateful to Dr. John G. Kirkwood for several illuminating discussions concerning a rigorous solution of the problem discussed in this paper. The authors are indebted to the Numerical Analysis Laboratory for the numerical integrations required for Figs. 2, 3 and 4. Thanks are also due to Miss Selma Hayman for the isolation of crystalline fumarase.
THE CRYSTAL STRUCTURE OF PERCHLORIC ACID MONOHYDRATE1 BY FREDERICK S. LEE AND GENEB. CARPENTER Corrlribution fi,orn the Metcalf Chemical Laboratories, Brown University, Providence, R. I . Received September 2 , 1968
The crystal structure of perchloric acid monohydrate hai been determined in detail by X-ray diffraction methods. The structure confirms that the solid is really hydronium perchlorate. The perchlorate ions are nearly perfect tetrahedra with an average C1-0 distance of 1.42 A.
Introduction Solid perchloric acid monohydrate has been regarded as a classic example of a hydronium salt on the basis of the qualitative similarity of its X-ray diffraction pattern to that of ammonium perchlorate2; however, no complete structure determination has been reported. Other lines of evidence have supported the hydronium-salt interpretation: nuclear niagnet,ic resonance, infrared spectra4J and Rnman spectrn.jt6 The purpose of the present work was to determine the crystal structure accurately in order to confirni the presence of the hydronium ion and to examine its hydrogen-bonding pattern. Determination of the Structure Sample.-Perchloric acid monohydrate was prepared by mixing the appropriate amounts of anhydrous and 72% acid. The material was sealed in thin-walled Pyrex capillaries to prevent the absorption of moisture during the X-ray examination. Sinall single crystals were then grown in the capillaries by zone melting; these were used for the Xray studies. The b-axis of the crystal normally grew parallel to the axis of the capillary; one crys( I ) This research was supported by the Office of Naval Researoh. Reyroduction in whole or part is permitted for any purpose of t h e United States Government. This work constitutes 1)art of the Ph.D. thesis work of F. S. L. Presented in part a t the San Francisco meeting of the Ainericaii Clieiiiical Society, April, 1958. ( 2 ) RI. Voliner, A n n . , 440, 200 (1924). (3) R. E. Richards and J. A. S.Smith, Trans. Faraday SOC., 47, 1261 (1951); Y.I
