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1 12 for his keen interest in the work and kind permission to publish the paper, and also to Mr. B. M. BISHUI, Assistant Director, for his invaluable suggestions and encouragement during the progress of the work. References ATMA RAM. BANERJEE, J. C. and NANDI, D. N. (1955). Trans. Ind. Ceram. Soc., 14, ATMA RAM. BISHUI, B. M. and PRASAD, J. (1960). Cent. Glass Ceram. Res. Inst. Bull., 7, BisHui, B. M. and PRASAD, J. (1959). Cent. Glass Ceram. Res. Inst. Bull., 6, CARTHEW, A. R. (1955). Amer. Miner., 40, GERARD-HIRNE and LAMY, C. (1951). Bull. Soc. Franc. Ceram., 10, MACKENZIE, R. C. and FARQUHARSON, K. R. (1953). C. R. XIX Congr. Geol. Inst. Alger., 18, MACKENZIE, R.C. and MITCHELL, B. D. (1957). "The Differential Thermal Investigation of Clays", Mineralogical Society, London, Chapter II. PRASAD, J. (1961). " Physico-Chemical Properties of Some Indian Clays and Related Minerals ", D. Phil (Science) Thesis, Calcutta University. SEWELL, E.C. and HOHEYBORNE, D. B. (1957). " The Differential Thermal Investigation of Clays", Mineralogical Society, London, Chapter III. SMOTHERS, W. J. and CHIANG YAO (1958). " Differential Thermal Analysis : Theory and Practice ", Chemical Publishing Co., N. Y., Chapter III. (Received, September, 3, 1964) Clay Science, Vol. 2, No. 2, pp , 1964 AMMONIUM CHLORIDE-KAOLIN COMPLEXES I. STRUCTURAL AND BONDING FEATURES Koji WADA Faculty of Agriculture, Kyushu University Introduction Rather common occurrence of salt adsorption on some soils and (43)

2 soil clays, particularly of amorphous nature, has been noticed in relation to their cation-exchange capacity measurement (WADA, 1964). Among several mechanisms, the intercalation of salt molecules in kaolin minerals has unique importance by virtue of their crystalline nature. Application of X-ray and infrared methods affords considerable scope for elucidation of the nature of the reaction between salts and minerals. The formation of interlayer salt complexes has been reported with halloysite (WADA, 1958 ; GARETT and WALKER, 1958 ; WADA, 1959), kaolinite (WADA, 1961; WEISS et al., 1963) and dickite (ANDREW et al., 1960), although the reaction with the latter two, polymorphs has been still questioned by some investigators (MILLER and KELLER, 1963). Complexes with NH4C1 are selected here in view of its simple composition and stable nature. The X-ray and infrared spectra data are given for the complexes of dickite-nacrite, kaolinite and halloysite. These data provide informations regarding to the nature of the bonding involved in the reaction, together with an unequivocal evidence for intercalation of NH4C1. 13 Materials and Methods The minerals used are a dickite from San Juanito, Chihuahua, Mexico, kaolinite from Birch Pit, Macon, Georgia, and hydrated halloysite from Yoake, Oita. The former two were obtained from Ward's Natural Science Establishment Inc., New York. The samples were lightly ground in a mechanical agate mortar and dispersed in NNaOH solution. The 2-20tt fractions were collected by sedimentation and used in this study. X-ray analysis indicates that the samples are pure except for the San Juanito dickite in which nacrite is intergrown. Respective NH4Cl complexes were prepared through KCH3COO complexes according to the procedure described in the preceding paper (WADA, 1963) with some modifications in detail of grinding and washing procedures. As a reference, NH4C1-mineral mixtures were prepared by adding NH4Cl in an aqueous solution to the oven-dry clay samples, mixing and air-drying. Total NH4 content of these samples (44)

3 14 was determined by microdiffusion analysis after digestion with concentrated sulfuric acid. Table 1 shows that the modifications in the preparative procedure adopted here result in higher retention of NH4Cl in the complexes than that reported before, while the complexes and mixtures are comparable in their total NH4Cl content. Table 1. NH4Cl content of complexes and mixtures (m. mols/100 g oven-dry clay). t NH4Cl: molecules per unit cell. X-ray patterns were obtained with powder or oriented specimens by means of a " Geigerflex " diffractometers. The infrared spectra were obtained with a Nihon-Bunko IR-S spectrometer using a NaC1 prism. Usually mg of a sample was mixed and pressed with mg KBr in a vacuum die. Results and Discussion X-ray Data The X-ray powder data for the NH4Cl-kaolin complexes are :shown in Table 2. The well-defined basal reflections appear at A and at its submultiples for all the minerals. This constitutes,a good evidence for intercalation of NH4Cl resulting in lattice expansion along the c-axis of the minerals. On the other hand, more numerous reflections, though sometimes blurred and diffused, are found for the dickite-nacrite and kaolinite complexes in comparison with the halloysite complex. It might be taken as an indication that the minerals react with NH4Cl resulting -in formation of new compounds, not simply the intercalation complex. This possibility, however, is readily eliminated by examining the diffraction pattern in more detail. All the strong (hk0) reflections, such as (020), (110) and (060), retain their spacings, and other reflections (45)

4 15 Table 2. X-ray powder data for NH4Cl-kaolin complexes. *1: Peak height read from recording chart. would also be indexed by assuming simple intercalation of NH4Cl without modification of kaolin layers. The latter is illustrated in Fig. (46)

5 16 Fig. 1. X-ray patterns of NH4C1-kaolin complexes (full line) and mixtures (dotted line). 1 and Table 3, where the X-ray patterns of the finger-print region:are shown together with calculated spacings and indices. In this tentative calculation, the unit cell was assumed monoclinic for the dickite and kaolinite complexes, and orthorhombic for the nacrite complex. The following parameters were used : where values for a0 and bo were assumed same as those of the original mineral (BRINDLEY, 1961). A relationship assumed between j3 values of the original mineral and complex is shown in Fig. 2. (47)

6 17 Table 3. Spacings observed and calculated, and indices for dickite-nacrite and kaolinite complexes. Many spacings calculated with the dickite and nacrite complexes are superposed. Only the calculated spacings with the former are shown unless indicated with * mark. Fig. 2. Relationship assumed between ƒà values of complexes (full lin e) and original minerals (dotted line). (48)

7 18 Fig. 3. Values of z parameters and configurations for an ideal NH4C1-kaolin complex. Table 4. Comparison of observed and calculated intensities of some basal reflertions for dickite-nacrite and kaolinite complexes. Iohs.* : Intensities estimated from peak height of basal reflections trom oriented specimens. See Fig. 3. (49)

8 The results suggest that the structural features of the respective complexes are largely inherited from the original minerals. The dickite-nacrite and kaolinite complexes likely reserve its own " threedimensional " regularity, whereas the halloysite complex exhibits only " two-dimensional" diffraction effect. Some displacements of the structural layers, however, can be deduced even for the former complexes of the higher crystalline polymorphs from the intensity distribution of the " 02, 11 " band (Table 2). Geometrically, there are two possible configurations for orientation -of NH4+ and Cl- between the structural layers (Fig. 3). The intensities of the basal reflections for these two configurations are calculated and compared with those found for the oriented specimens (Table 4). On this basis alone, however, no definite conclusion can be drawn as to which configuration is preferable. Less ambiguous choice will be made taking consideration of the infrared data regarding to bond formation. 19 Infraed Data The numerical infrared data for the NH4C1-kaolin complexes and those for NH4Cl are listed in Tables 5 and 6, respectively. The assignments of the respective bands are based on earlier works.(stubican and ROY, 1961; WAGNER and HORNIG, 1950). As an example, the spectra of the dickite-nacrite complex and mixture together with that of NH4Cl alone are also given in Fig. 4. The infrared spectra of the three complexes have certain features in common. The OH and OH...O vibrations of the minerals are largely affected by intercalation of NH4Cl. The structural assignment of OH and OH...O stretching vibrations for kaolin minerals is still in dispute.(van der MAREL, 1959 ; NEWNHAM, 1961 ; WOLFF, 1963 ; SERRATOSA, et al. 1963). The modification caused by intercalation can be used as an effective means for the purpose. Unfortunately, the resolution of the spectrometer used here is not high in the region and does not permit detailed interpretation. Upon intercalation of NH4Cl, however, the 3685 to 3700 cm-1 peaks apparently disappeared and remained as (50)

9 20 Table 5. Assignments, frequencies and relative intensities of infrared absorption bands for NH4Cl-kaolin mixtures and complexes. Relative intensities were estimated from log(1/t) where T is transmission %. No partitioning was carried out even for overlapping bands. * Assignment ; OH(in H2O)-deformation. a faintly visible shoulder. This indicates that a majority or at least some of the hydroxyls which contribute to this absorption are (51)

10 21 Table 6. Assignments, frequencies, and relative intensities of infrared absorption bands for NH4C1. * Data from WAGNER and HORNIG (1950). v1 to v4; see Table 7, v5 and v6; lattice õ vibrations. Fig. 4. Infrared spectra of dickite-nacrite complex, mixture and NH4Cl. exposed at the interlayer surface. The intercalation also resulted in a partial yet clear shift on the deformation band of the structural hydroxyls from 930 to 970 cm-1. It can be inferred therefore that the (52)

11 cm-1 absorption also arises from the hydroxyls exposed at the interlayer surface. The OH...Cl interaction in the complex can be deduced on the following observations. 1. The slight decrease in some of the OH stretching frequencies with a displacement of about 50 to 80 cm The increase in the peak intensity of the OH stretching vibrations except for that at cm The shift of the OH deformation peak at 930 to 970 cm-1. These are the direction of the change that is expected for the OH...C1 interaction in the complex due to a possible, closer contact between OH and Cl- than that between OH and O in an adjacent layer in the original mineral. The shift of the OH stretching frequencies is similar in magnitude to that found between cis- and transo-chlorophenol, namely, (PAULING, 1960), and more generally, to those found for formation of intramolecular hydrogen bonds in some diols (PIMENTEL and MCCLELLAN, 1960). The OH...N (NH4) interaction may not occur due to instability caused by the repulsion of the similarly charged hydrogen atoms. Indeed, there is no indication for formation of such a bond as shown below. Intercalation of NH4Cl results in appearance of additional bands together with a notable sharpening of all the NH4Cl bands in the spectra (Table 5 ; Fig. 4). The result can be interpreted in terms of the lower symmetry of NH4+ oriented (C,) than that in the free salt (Td ). Many experimental data are available to show that this type of lowering of symmetry splits the degenerate vibrations and activates originally forbidden vibrations (NAKAMOTO, 1963). Only two examples are quoted here in comparison with the band assignment made for the present case (Table 7). No hydrogen bond of the NH...O type appears to form. Instead, the three hydrogen atoms of the NH4+ point to three adjacent Cl- and one remaining hydrogen atom is in the relatively free state. The sharpening of the NH bands is particulary remarkable for (53)

12 23 Table 7. Correlation and assignment of vibrational frequencies of free (NH4) and intercalated (HNH3) ammonium ions. v ; stretching, Ý ; deformation, pr ; rocking, s ; symmetric, d ; degenerate. * Infrared inactive vibration. fi Data from NAKAMOTO (1963). higher crystalline polymorphs (Fig. 4), indicating that NH4+ is in a definite configuration. The large difference in the band intensities between the corresponding complex and mixture may be attributable largely to the difference in the crystallite size of NH4Cl, namely in monomolecular layer vs. in micro-crystallite. In the case of halloysite, where this difference is relatively small (Table 5), a considerable orientation of NH4Cl on the external surface is suggested. A sharpening and resolution of the SiO band occur as a result of complex formation (Fig. 4), suggesting partial elimination of lattice vibrations. Also, the intensity of the band near 800 cm-1 in the original mineral decreases remarkably for the higher crystalline polymorphs, whereas the same absorption is very weak for halloysite regardless of intercalation of NH4C1 (Table 5). STUBICAN and ROY (1961) made an assignment Si-O-(Al) to this band, and the present result indicates that this band is also sensitive to the interlayer bonding. (54)

13 24 Summary and Conclusion X-ray data indicate that the NH4Cl complexes of the kaolin polymorphs have major structural features in common but differ in the stacking of the layer sequence. The latter feature appears to be largely inherited.from the original mineral ; the dickite-nacrite and kaolinite complexes retain " three-dimensional " regularity, whereas the halloysite complex shows only " two-dimensional " diffraction effect. The infrared data show a lowering of the symmetry of NH4+ (Td to C3 ) and formation of the OH...CI type long hydrogen bond in intercalation. No indication is given for formation of a NH...O bond. From the evidences brought together in the present and preceding studies, it is concluded that the NH4Cl-kaolin complex is a " clathrate compound " in which molecules are entrapped by a lattice formed by other molecules. The bonding involved is mainly due to van der Waals forces, and to some extent, to a long hydrogen bond of the OH...CI type. The configuration A in Fig. 3 is suggested for an ideal NH4Cl-kaolin complex. This satisfies geometrical requirements, orientation maximum (two molecules per unit cell) and bond relationship. References ANDREW, R. W., JACKSON, M. L. and Wada, K. (1960). Soil Sci. Soc. Amer. Proc., 5, BRINDLEY, G. W. (1961). The X-ray Identification and Crystal Structures of Clay Minerals (Edited by Brown, G.), Mineralogical Society, London, Chapter II. GARETT, W. G. and WALKER, G. F. (1959). Clay Minerals Bull., 4, MAREL, van der H. W. (1959). Silicates Industriels (Belgique), 24, MILLER, W. D. and KELLER, W. D. (1963). Clays and Clay Minerals, 10, NAKAMOTO, K. (1963). Infrared Spectra of Inorganic and Coordination Compounds, John Wiley & Sons, Inc., 110. NEWNHAM, R. E. (1961). Miner. Mag., 32, PAULING, L. (1960). The Nature of the Chemical Bond, Cornell University Press, 492. (55)

14 PIMENTEL, G. C. and MCCLELLAN, A. L. (1960). The Hydrogen Bond, W. H. Freeman & Co., 97. SERRATOSA, J. M., HIDALGO, A. and VINAS, J. M. (1963). International Clay Conference 1963, STUBICAN, V. and ROY, R. (1961). Zeit. Krist., 115, WADA, K. (1958). Soil Plant Food (Tokyo), 4, WADA, K. (1959). Amer. Miner., 44, WADA, K. (1961). Amer. Miner., 46, WADA, K. (1963). Amer. Miner., 48, WADA, K. (1964). Clay Sci. (In Japanese), 4, WAGNER, E. L. and HORNIG, D. F. (1950). Journ. Chem. Phys., 18, WEISS, A., THIELEPAPE, W., GORING, G., RITTER, W. and Schafer, H. (1963). International Clay Conference 1963, WOLFF, R. G. (1963). Amer. Miner., 48, (Received, September 20, 1964) 25 Clay Science, Vol. 2, No. 2, pp , 1964 DIOCTAHEDRAL CHLORITE FROM THE FURUTOBE MINE, AKITA PREFECTURE, JAPAN Noboru TSUKAHARA Mining Department, Sumitomo Metal Mining Co., Ltd. Abstract The specimen was taken from the argillaceous altered zone (Tertiary rocks), which lies in the horizon corresponding to the foot-wall of the Daikokuzawa ore deposit of the Furutobe mine. Two specimens, numbered F-11 and F-19, are studied in this paper. Their color is white but is slightly grayish. The specimens are composed almost entirely of dioctahedral chlorite, accompanied by small amounts of quartz, illite and pyrite. The chemical compositions of F-11- MR18-64, which is the sample purified from F-11, are as follows : SiO2 : 39.01%, TiO2 : 0.47%, Al2O3 : 32.15%, Fe2O3 : 0.90%, FeO : 0.10%, MgO : 10.14%, CaO : 0.54%, Na20 : 0.10%, K20 : 1.52%, S : 0.42%, (56)

THE USE OF PIPERIDINE AS AN AID TO CLAY-MINERAL IDENTIFICATION

THE USE OF PIPERIDINE AS AN AID TO CLAY-MINERAL IDENTIFICATION By J. M. OADES* and W. N. TOWNSEND Department of Agriculture, The University of Leeds. [Received 30th August, 1962] ABSTRACT It is suggested