nith high boiling points, n i t h the exception of aluminum salts. TCA was chosen as protein precipitant CT en though the enhancing effect of this reagent does not rearh a plateau. -it long as the concentration of TCA in sample and standards ismithin A0.3y0of each other, the resulting relative error is negligible. Variations in TCh concentrations due to the sliding scale of urine dilutions result in a maximum error of in estimated calcium concentration. TCA has the advantage of yielding a clear supernate and results in complete release of the protein-bound calcium. \\-bile PTX has no effect on calcium emission, it does not uniformly release calcium from calcium-proteinates. Perchloric acid precipitation results in a turbid supernate which tends to clog the burner capillary. Normal Values f o r Serum Calcium. I n a group of 100 healthy medical students the serum calcium level was found t o be 5.15 ~ 0 . 2 5meq. per liter ( 1 2 std. dev.). The relative standard deviation of the method is *1.5% for serum (repeated determinations on 20 sera over a 10-day period), and +2% for urine (in various dilutions tested repeatedly over a 10-day
period). The relative standard deviation of 6 to 8 replicate serum determinations performed on the same day with the same pipet is 10.57, (semiautomatic constriction micropipets from Carlsbwg laboratories, Copenhagen, Denmark). Recovery of calcium added to serum and urine samples is 100 1 lYc (standard deviation of mean).
Boyle, A. J., Am. J . C h a . Path. 22 687 (1952). ( 14) Kingslev, G. R., Schaff ert, It. R., J . Bzol. Chem. 206, 807 (1954). 113) i\lacInt\re. I.. Biochem. J . 67, 164
(10.57).
“
(16) Margoshes, RI , 1-allee, H I), A v 4 r ) . CHEM.28, 180 (19%). (17) Ibid., p. 1066. (18) lIosher, It. E., Itano, RI., Boyle,
A. ,J , Myers, G. B., Iseri, L. T., Am. J . Clzn. Path. 21, i 5 (1951). 11‘31 Poulos. P. P.. Pitts. R. F..’ J . Lab. elin. X e c i . 49, 300 (19i7). LITERATURE CITED (20) Saha, K , N., “A Treatise on Modern Physics,’’ 1-01. I, Indian Press Ltd., (1) Baker, G. I,., Johnson, L. H., AXIL. Calcutta, 1934. (21) Severinghaus, J. W., Ferrebee, J. IV., aker, I{. IT. It.; Biochem. J . 59, J . Biol. Chem. 187,621 (1950). 566 (1‘355). (22) Thiers, R. E., Hviid, Kirsten, C h i . ( 3) Butterworth, E. D., J . Clin. Path. 10, Chem. 8, 35 (1962). 3 i 9 (1957). (23) Toribara, T. Y., Dewey, P. A., (4) Caton, R. D., Bremner, R. IT., A N ~ L . Warner, €I., ANAL. CHERT.29, 540 CHEY.26, 805 (1954). (1957). (~, 5 ) Chen. P. S..Toribara. T. Y.. I b i d . . (24) Valencia, R., Bull. SOC. Chim. Biol. \~
25, 1642 (1953). (6) Ibzd., 26, 1967 (1954). (7) Denson, J. R., J . B i d . Chem. 209, 233 (1954). (8) Dorche, M. J., Costet, C., Ann. Pharm. Francaises X I V , 669 (1956). (9) Dreissbach, It. H., ASAL. CHEX 31, 479 (1959). (10) Foster,’ W. H., Jr., Hume, D. K., Ibid., 31, 2033 (1959). (11) Huldt, L., d r k i v for Matematik, Aslronomi och Fysik 33.4, 1 (1946). 112) Jackson, W. P. U., Irwin. L.. J . Clin. Path. 10, 383 (1957). (13) Kapuscinsky, Ir., Moss, N., Zak, B.,
38, 1071 (1956). (25) Winer, A. D., Kuhns, D. RI., A m . J . Clin. Path. 23, 1259 (1953). (26) Yofe, J., Finkelstein, R., Anal. Chim. Acta 19, 166 (1958).
RECEIVED for review October 1, 1962. Accepted March 21, 1963. This work x a s aided by grants from Ayerst Laboratories, RIerck Sharp and Dohme Laboratories, G. D. Searle and Co., The Upjohn Co., U. S. Public Health Grant CYP-3488,
and institutional grants allocated by the Committee on Research of the Academic Senate of the University of California.
Studies in the Structure of Organic Peroxides DANIEL SWERN and LEONARD S. SILBERT Eastern Regional Research laboratory, Philadelphia 7 8, Pa.
b Infrared, dipole moment, and molecular weight studies have shown that peroxy acids exist in solution exclusively as intramolecularly hydrogen-bonded monomers containing a puckered five-membered ring. In the solid state peroxy acids exist as dimers. Diacyl peroxides and fertbutyl peroxy esters also have a skewed structure in the peroxide grouping. Polarography permits the establishment of an order of stability of organic peroxides which parallels their energy of activation for thermal decomposition and reactivity with iodide ion. the past decade considerable information ha3 been acquired on the structure of several important classes of organic peroxides, but the picture is not yet complete. S u merous approaches have been applied, both singly and in combination, to the elucidation of their structures, including, among many other techniques, analytical, spectral, polarographic, x-ray dif-
fraction, and dipole moment studies. The structural problems will inevitably be completely solved b y such a broad approach using every physical and chemical tool available. The major portion of this paper is devoted to the structure and properties of three important classes of organic peroxides: peroxy acids, diacyl peroxides, and tert-butyl peroxy esters: 0
0
/I
I1
R-COIH R-C-0-0-C-R Perosy acids Diacyl peroxides 0
II
R-C-O-O-Bu( t) fert-Butyl perosy esters
ITHIN
880
ANALYTICAL CHEMISTRY
ORGANIC PEROXY ACIDS, R-COIH
For many years, it has been known that peroxy acids contain one more oxygen atom than the corresponding carboxylic acid
