164. Basic Lead Carbonate, 2 PbCO3.Pb(OH), GERALD KATZ and ROBERT LEFKER Signal Corps Engineering Laboratories, Fort Monmouth, N. J.
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of basic lead carbonate have been prepared hydrothermally ( 2 ) . Finely divided powder of t h e tetragonal polymorph of PbO and distilled water were heated in a n autoclave to 440’ C. a t 18,000 pounds per square inch for the crystal growth. The lattice constants were determined using the graphical method of successive approximations (4). The calculations were made on the IBM-650 calculator; 19 iterations were used. RYSTBLS
CRYSTAL MORPHOLOGY Crystal System. Hexagonal. Form and Habit. Clear transparent platelets with hexagonal shape. M a n y crystals exhibit a dihexagonal (12sided) morphology. X-RAYDIFFRACTION DAT.4 Three Possible Space Groups. P63/ mcm, Pg3cm, PGc2. Cell Dimensions. a, = 9.1064 f 0.0001 A,, c, = 24.839 f 0.001 X., c/a = 2.728 i: 0.001 at 21.1’ C. Cowley (1) reports a, = 9.06 A., c, = 24.8 A., c / a = 2.74. Formula Weights per Cell. 9. Formula Weight. 775.6. Density. 6.51 grams per cc. (x-ray). Cowley (1) calculates 6.57 per cc. from electron diffraction data. Literature reports range from 6.14 t o 6.81 grams per cc. OPTICAL PROPERTIES Uniaxial negative, optic or c-axis normal t o datelet. Omega 1.75. I n agreement with d a t a of Merwin (3) as described by Winchell ( 5 ) : “Pb3(OH)a(C03)2 is hexagonal in basal plates with a : c = 1.419. Soft, perfect 0001 cleavage. G = 6.14. Soluble in dilute ”I3. Uniaxial negative with N o = 2.09, Ne = 1.94, N o - .Ve = 0.15 colorless. This is the pigment called ‘white lead.’ T h e natural mineral is called hydrocerussite.”
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LITERATURE CITED
(1) Cowley, J. M., Acta Crust. 9, 391-6 (1956). (2) Katz, G., Reed, L., Ibid., 10, 142 (1957). (3) Merwin, H. E., Proc. Am. Soc. Testing Materials XVII, Pt. 2 (1917). (4) Taylor, A., Floyd, R. \T7,, Acta Crust. 3,285 (1950). (5) Winchell, A. N., “hlicroscopic Characters of Artificial Minerals,” 2nd ed., p. 203, Wiley, New York, 1931. CONTRIBUTIONS Of crystallographic data for this section should be sent to W. C. McCrone, 500 East 33rd St., Chicago 16, Ill.
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ANALYTICAL CHEMISTRY
Reflections Used in Determination of Lattice Constants of Hexagonal 2PbCOs.Pb(0H)z by Graphical Method of Successive Approximations hk.1 x d, A., Obsd. B. Evaluation of co A. Evaluation of a0 31.25 CU K a 0.90592 62.21 CU Kai 0.80304 64.3 CU Kai 0,89855 62.21 CU Kaz 0.80319 64.3 CU Ka? 0.89885 0.85549 Wavelengthsused. Cu Kal = 1.5405024. 82.3 CU Kai 82.3 CU Kaz 0.85579 CUKai = 1.54434 -4. 91.2 CU Kai 0.82455 CU Ka = 1.5418.4.
Partial Powder X-Ray Diffraction Pattern of Basic Lead Carbonate, 2 PbCOS.Pb(OHh d, A., d, A., d, A.1 d, - 4 . 1 hk-I Calcd. Obsd.a I/I? hk.1 Calcd. Obsd.a I/Ilb 20.14 2 7.87 10.0 7.88 1.617 32.7 6.63 5 10.2 6.65 1,604’ 1.602 2, broad 22.11 2 4.89 10.4 4.88 11.15 1 559 4.46 2 11.1 4.48 8 1 556) ’ 554 00.16 4.26 9 11* 2 4.27 1.545 1.540 3 40.10 8 3.97 11.3 3.99 1,527 21.14 2, broad 1 3.72 20.2 3.76 1.526) “j2‘ 10.16 9 10.6 3.67 3.66 41.8 5, broad 1.505 10 20.4 3.33 3.34 31.12 8 3.07 11.6 3.05 1.466 42.3 21 .o 2.981 7 , broad 22.13 2.95 8 21.1 1.463 32.10 r 21 * 2 2 1.447 1.444 20.16 2.89 2.89 10.8 51.0 2 r 21.3 2.80 41-10 2.79 11.7 2.80) 51.2 1 2.67 2.69 21.4 2, broad 50.8 2.61 9 2.63 30.0 42.6 30.2 51.4 1 2.55 11.8 31.14 2, broad 2.56 21.5 21-16 9 2.48 2.49 00.10 42.7 30.4 2, broad 51.5 5 2.41 21.6 51.6 2 1 2.36 2.36 11.9 30.16 21.7 40.14 7 2.27 22.0 2 51-7 2.27 22.1 32 * 13 8 2.22 2.22 30.6 2 42.9 2.186 31.0 1 43.2 i 2,1841 2.176 11.10 41.13 5, broad 2.177J 31.1 42 * 10 2 2.132 2.137 22.4 31.16 1 7 2.058 2.062 31.4 1.262 52.0 2.027 21.9 1,256‘ 52.2 2.027 8 2.026) 1.995 11.11 2, broad 1.255. 1.285 50.12 2 1.987 22.6 1.254 21.18 1.936 5 1.934 31.6 1.245 00.20 2, broad 1.905 5 1.910 21.10 42.11 1.878 40.4 51.10 5, broad 1.870 2 1.862 31.7 10.20 1.836 22.8 40.16 1.828 5 5 1.835 20.12 43.7 1.807 30.10 61.2 5 1.801 9 1.803 32.1 43.8 1.802J 21.11 5 20.20 1,767 32.3 1 42.13 1,765 2 1.765) 11.13 2 42.14 2 1.758 1.757 22.9 Philips 114.6-mm.-diameter powder 2, broad 1.699 1.702 21 12 camera, Straumanis mounting, (CuKa) = 8 1.693 1,699 32.5 1.5418. 1.674 5 1.679 22.10 Relative intensities from visual esti32.6 1.653 2 mates above background. 11.14
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