ATOMIC STRUCTURE MODELS FOR CLAY MINERALS ALFRED T. PERKINS Agricultural Experiment Station, Kansas State College, Manhattan, Kansas
T H m E are several different sets of commerrial models ;~vailablet o demonstrate the atomic structure of chemiral compounds. These srts in general are exrellent for rcrtain purposes but thry all lack (iesirnl)le fea,t.urer for illustrating t,he spare-lat,tice ronfiguration of the rlay minerals and are some\\-hat expensive. T h r Follon-iny described atomir strnrturr models of cia?- rninrrnls 11sc rheap mat,eri;ds, i n ~ o l v ea minimum nf (.a41 ont-
Aluminum a n d Magnesium. Oxygen. H y d r o i d . Octahedrons
to stand overnight and t,I~enallowed to dry to srlrlr a moisture content that the individual atom r e p l i ~ wwill t~oldtheir shape ~vithontslumping while drying. The size of t,he individual atoms may be determined hy reference t,oPading (1) or Marshall (3) or ot,her authors, and a convenient ratio to use in constructing the at,oms is 2.5 cm. per Angst,riim unit. The amount of ria? required to construct each atomic speries to size may Ile det,erminrd 11y trial and error and the mount of d a y rnplirated hp \,-eight or measured volume. The h m p s of clay may he rolled into almost pwfcv.t spheres hy rolling them hetwecn the palms of the h:mtls. If sufficiently dry d a y is used to prevent slumping on drying, a 'rark may appear in the surfarr of the sphere. Such cracks may be eliminated by nthbing t,l~rmwith a wet finger. The t~allsor atomic replicas may hr held in desired positions, such as the hexagon rings characteristir of the rlny minerals, l y steel ~virrs. The maintenanre of the position of the balls whilt~ const,rrrcting the spare lattice configorat,ion mxy 11r rffrcted hy thr use of a piere of wood or similar material with holes ~lrilledin the proper positions. Tht. individual gr1111psof atom rrplicas should he thoroughly air dried, then d r i ~ din the 100°C. oven, and the11 firer1 in afurnacr at ahout 650" so as to set the clay. Aft,er cooling, the individual atoms may be painted wit,h - ~ - -water rolors followed bv a coat of clear larorter. and a stable model uill rekrllt. If desired a mt~ch higher temperatrlre may he used for firing so that the l.ltly \,-ill vit,rifl., mzlking chinw or porrelain models, ~~~~
lay, imd may easily he made to demonst,rate thr s1)xrt.Iattive structure of minerals ~ I accord I with the scientist'* desires. With reasonahlr care and patience the modrls very refined model. The structure of clav minerals has been studied bv Pauling ( I ) , Bragg ?I?), Marshall (S), C r m (4j. Henrlricks (5), and many others and they have used \vootl balls, rubber halls, glass marhles, plimtic mnterials, and paper forms to demonstrate and ? ; t ~ ~ thr dy cryshl lattice of the clay minerals. Excellent m~rlrls h a w been made but. in most cases the cash rost of nirh modcls has been an undesirable factor. The models described herein may be made with an>good ceramic clay that may be dug in many localit,ies or ourchased from commercial concerns.' s t r d wire of almnt 10 gage, water colors, clear larqner, and a muffle ir~rnare. The rlav should he \\-el1 vetted and allowed
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Art Cle3- Co., Indiun~polis,Indiana, or local arhaol
oxygen. oxygen~ y d r o x a l .and ~ v d r o x a ~l a y e r rof clays
supply stor?.
388
JULY, 1951
but it does not seem that the resultant models would be sufficientlyimproved to warrant the extra work. Any good book on pottery or china manufacture, such as Jenkins (6), would contain many helpful hints to the scientist who wishes to construct models of atomic structure. LITERATURE CITED PAULING, LINIIS, "The Kature of the Chemical Bond," 2nd ed., Cornell University Press, Ithaea, New York, 1948. BRAGG, W.L., "Atomic St,ructure of Minerals,"Cornell Uni. versity Press, Ithaca, A-ew l'ork, 1937. n l a n s x n ~ ~C., EDXJNI,,"The Colloid Chemistry of the Silicate Minerals," Academic Press, h-ew York, 1949. GRIM,RALPHZ., "Modern concept of clay minerals," J. Geol., 1, 225-75 (1942). HENDRICRS, S. B., "Base exchange oi crystalline silicates," Ind. Eno. Ckem.., 37.625 (19451. . . . (8) JENKINS, R. H., "Practical Pottery," The Bruce Puhlisliing Co., Milwaukee, 1941.
Kaolin Showing Silicon. Aluminum, Oxygen. and Hydroxal Units
