NBS MONOGRAPH 14

Bibliography on IVIolecular and

Crystal Structure Models

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UNITED STATES DEPARTiMENT OF COMMERCE • Frederick H. Mueller, SecrHary

NATIONAL BUREAU OF STANDARDS • A. V. Astin, Direcior

Bibliography on Molecular and

Crystal Structure Models

Deane K. Smith

National Bureau of Standards Monograph 14

Issued May 20, 1960

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. - Price 15 cents
Contents

Page

Foreword iii

i 1. Introduction 1 [2. Organization of the bibliography . 1

I 3. Models in general 1

: 4. Static models 2

j 5. Closed models 2

5.1. Closed molecular models 2

5.2. Closed packing models 3

6. Open models 3

6.1. Open molecular models 3

6.2. Open structure models 3

6.3. Open models with parallel rods 3

7. Polyhedral models 4

8. Miscellaneous types 4

9. Dynamic models 4

10. Construction devices 4

11. References 4

11.1. Models in general 4

11.2. Static models 5

a. Closed molecular (Stuart type) 5

b. Closed packing type 5

c. Open models (molecular, bond type) 6

d. Open models (crystal, bond type) 6

e. Open models (vertical rods) 6

f. Polyhedral models 6

g. Miscellaneous model types 7

11.3. Dynamic models 7

11.4. Construction devices 7

IV
Bibliography on Molecular and Crystal Structure Models

Deane K. Smith ^

A bibliography on molecular and crystal structure models is presented. The references are classified into those discussing models in general, static models, dynamic models, or construction devices. The static models are further classified in molecular (Fisher-HirschfelderTaj'lor type), closed packing, open molecular, open crystal structure, open with parallel rods, polyhedral, and miscellaneous models. A short annotation is given which describes the model

tj'pes and indicates the more significant articles pertaining to them.

1. Introduction

The mounting volume of literature on molecular

jind crystal structure models reflects their increasilng importance in modern scientific research. The

toginal use of models for depicting atomic arrangefients is obscure, but it may date back to Kepler

1611) in his Strena seu de nive sexangula. As early

s 1690 Huygens, in his Treatise on Optics, conpidered the calcite structure to be composed of a

lihree-dimensional array of flattened spheroids.

iHaiiy (1784) in his Essai d'une theorie sur la structure des crystaux appliquee d plusieurs generes de

'substances crystallisees pictured the calcite structure as consisting of a three-dimensional array of unit rhombohedra and showed the relation of these

lunits to the usual scalenohedral habit of crystallized calcite. Frankenheini (1842) and Bravais

,(1848) show a baU-and-spoke representation of the

(14 space lattices. However, it was Pasteur (1848), van't Hoff (1874), and Le Bel (1874) who used the

first truly molecular representations in their work

on optically active compounds. Barlow (1884,

il897), Kelvin (1889), and Barlow and Pope (1906,

11907, 1908, 1910) used packing models incorporatling spheres to explain hexagonal and cubic close

jjpacking and some simple crystal structure types,

i Since 1912, when the use of X-rays for deterimining crystal structures had its beginning, models

/have played an even more common role as an imiportant research tool. Besides being used as an

(instructional aid in classrooms, many types of

' structure models are used extensively in research

laboratories throughout the world. Even re- searchers who can "think in three dimensions"

find that the time spent in constructing a model is usuaUy justified because the mutual relations of

the atoms are much more apparent in the model.

The model is often an aid to the chemist for inter1 preting the results of structure analyses. Chemical

1 reactions and the physical properties of crystalline

[ material, such as optical, elastic, electrical, mag-

" netic, and thermal properties can be qualitatively

' correlated with the crystal structure most easfly

when a model is available. Models are now beingused as research tools by physicists, chemists,

geologists, metallurgists, and biologists.

; Special models have been developed to interpret

I many properties of cleavage, stacking disorder,

deformation under mechanical stress, isomerism,

Research Associate, Portland Cement Association Fellowship.

and steric hindrance. Further developments in

the field of specialized models are the dynamic or working models. These models represent atomic

and molecular movements and interactions which

take place during chemical and physical processes. Such effects as thermal motion, phase changes, and

dislocations or disruption of ordered arrays by

foreign ions have been well illustrated by working

models.

2. Organization of the Bibliography

Because of the ever-increasing use of structure models in scientific research and the widely

scattered literature on them, it was felt that a bibliography covering the various types and uses, conventions as to scale and other characteristics,

and construction techniques would be useful,

especiaUy for anyone planning to construct a model for the first time. This bibliography

includes most of the readily available papers, but some references in less accessible journals have

probably been missed. Also missing are references

to many variations in models developed for special

purposes that unfortunately have never appeared

in print.

The references in this bibliography have been

grouped into four broad categories: Models in

general; static models; dynamic models; and

construction devices. Only the static models have

been further subdivided, because they are the most

common and show a great divergence of types.

Many of the static models are actually combinations of two or more basic types. Thus a clear-cut

subdivision is quite difficult. Four subgroups have

been used: closed models, open models, polyhedral

models, and miscellaneous. Each reference has

been classified as far as possible according to the

dominant features of the model described.

3. Models in General

Because of the wide variety of structure model

types, very few papers were classified as general in content. Only the discussion by Nicholson (1952)

is really a survey paper. He describes several

types of crystal models seen in various laboratories, some of which are not described elsewhere in

the literature. These previously undescribed types

are an indication that many types of models

developed for specific uses have never been

described in the literature. Gibb and Winnerman

(1958) discuss the applications of crystal models.

1
particularly packing models, for understanding

salt reactions. Bragg and Bragg (1929) have

compiled a set of stereophotographs of crystal

structui'e models of several types.

Other general papers contain the color and size standards established by the British Institute of

Physics (1947) which is generally followed in the

United States. This same code is reproduced by

Lipson and Cochran (1953). A few variations

from this code do occur; for example, white is as commonly used for silicon as is the black listed in

the specifications. In some of the more complex

mineral structures which contain several different

metal atoms, the color code has been altered. Also in the Fisher-Hirschfelder-Taylor model sets, blue is used for oxygen instead of red. Thus

anyone inspecting any model for the first time

must check the identification of the atoms.

A compilation of bond angles and interatomic

distances in molecules and ions, which is useful to model builders, has been edited by Sutton (1958).

It includes data obtained by spectroscopy and

X-ray, electron, and neutron diffraction up to and including the year 1955. Another source

for this information is the Groth Institute at the

Pennsylvania State University.

4. Static Models

Static models, in contrast to the dynamic

models, are very widely used at the present time.

They are primarily employed to depict accurately

the relative atom positions and bond angles in either molecules or crystals. Two main types

of these models exist. In the first, the atoms are represented by spheres scaled to the effective

atomic radii, and the model consists of these

spheres placed in contact in their respective positions. The internal portions of these models are not usually visible, and this type of model will be termed closed. The second type, which will

be termed open, consists of units representing

atoms, usually spheres of wood or plastic, linked

by rods representing the bonds. These open

models show valency angles, interatomic dis- tances, and symmetry more clearly than do the

closed models. However, only rarely is any

attempt made to represent atomic radii with the

size of the spheres, and this type of model is not

so easily used to study spatial relatioias and steric

hindrance as the closed type. The wire models

may be considered open models in which the balls representing atoms have shrunk to the vanishing

point.

A few additional types of static models exist

which cannot be placed in these two main classifications. Of these, only the models made with

coordination polyhedra warrant separate mention.

The polyhedral model was developed primarily as a money and time saving structural representation

which generally depicts the arrangement of anions

about each cation or the closest neighbors around

a carbon atom.

5. Closed Models

5.1. Closed Molecular Models

The closed models may be subdivided into two

types, which, however, are not completely distinct,

j The first type, commonly called the Fisher-

Hirschfelder-Taylor models (abbreviated henceforth as F.H.T.), are usually attributed to Stuart

(1934). Discussions on the theoretical aspects : of these models are given by Wepster (1946, ; 1951), Taylor (1941), Briegleb (1950 a, b), and

' Hartley and 'Robinson (1952). The F.H.T. models |. consist of plastic or wooden spheres whose radii ! are proportional to the Van der Waals radii, and ; whose colors (with some exceptions) correspond ' to the British code. These spheres are flattened;' by cutting along planes normal to expected bond '' du'ections by an amount corresponding to the|

difference between the Van der Waals radii and'' the single, double, or triple covalent bond radii. ' Thus for a given element several different atom

,

models may be necessary; for example, five; different models of the carbon atom are used to; represent the five most common combinations

of single, double, and triple bonds in which it i occurs. In the early models of the F.H.T. type, the

atoms were bonded with wooden pegs which permitted rotation of atoms around single bonds but

yielded a model with poor tensUe strength. | Consequently, several types of snap fasteners have ' been developed, notably by Taylor (1941, 1943) ' and Hartley and Robinson (1952). Casler and

Corey (1958) describe a magnetic coupling used

primarily for hydrogen bonds. , The F.H.T. models incorporate several desirable j features. (1) The models are quickly constructed,

and most molecules can be made or at least ap-

,

proximated. (2) The size of the model closely,

represents a scaled-up molecule. (3) The space-

(

filling characteristics are easily observable. (4)

,

Steric hindrance may be observed by using j rotatable bonds. Briegleb (1950) and Hartley

j and Robinson (1952) list several shortcomings

of the standard F.H.T. model and suggest modi-t

fications which wUl allow the bond angles to bef, distorted up to 12° and give the model somoj

flexibility. Both the F.H.T. models and the(

Courtauld (Hartley and Robinson) models are]

commercially available through chemical supply ; companies. Recently Godfrey (1959) has de-f

scribed a slightl}^ modified F.H.T. model which is also commercially available.

The recent availability of spheres of several,

colors and sizes made from foamed polystyrene

has led several people, notably Lambert (1953), i to construct their own Stuart models. The spheres I are given flattened surfaces normal to bond direc

tions as in the F.H.T. models. They can be bonded ; temporarily by metal rods or pipe cleaners or i permanently by glues.

2
'I f

5.2. Closed Packing Models

The second type of closed model is the packing

j paodel. The main distinction between this model

V, and F.H.T. type is that the atoms are assumed to

oe spherical, and the radii of the spheres are made

f- proportional to ionic, metallic, or covalent radii of

•^' Ihe represented atoms. Spheres of wood, cork,

foamed poh-styrene, and plastics have been used

m these models. Whereas the F.H.T. models are

aiost applicable to organic models, the packing

model is more suitable for representing inorganic

^ijsrystal structures, especially those with metallic

.(jf.and ionic bonding.

Packing models are constructed by marking on

die surface of each sphere all the bond dii'ections and gluing or pinning the spheres at the appro-

'priate points of contact. Plastic balls may be

r^ijglued by placing a drop of solvent at their point

':'m contact. Buerger and Butler (1936) have

described the process fairly completely. Davidson

(1952) describes the use of cork balls, and Hatch,

!^ Comeforo, and Pace (1952) and Ordway (1952)

J'idescribe models made with hollow, transparent

^ plastic spheres. The use of foamed polystyrene

*' spheres is discussed in the paper on a punching jig

Iby Gibb and Bassow (1957).

6. Open Models

In the open models the balls representing the

fjjjatoms do not touch; instead they are usually

jjjiconnected by rods representing the bonds. The

^ilballs may or may not be scaled in diameter. In

/'these models the atoms within can be seen as well

las those on the sm-face, and thus this representa-

, i^'tion is more suitable for complex structures and

•*| ;for photographic illustration. The symmetry and

'^iiilbond patterns are more easUy visible, but the pack-

^iiing characteristics of the atoms are not so apyjjparent. In general, it is easier to construct an

^|iopen model of a distorted molecule than a closed

'Ijione if the departures from regiilar arrangement

^ajqare large.

If The open models have been divided into three

?]l groups. The first group contains molecular models

"which are primarily organic in nature, and the

*

' Second group contains the more general structure

- models. The models of both these groups have

sometimes been called the "ball and spoke" type.

'fjl'The third group consists of vertical rods mounted

!|] at certain positions on a base plate and supporting

"•'balls at specific heights.

J 6.1. Open Molecular Models

,e ,. The open molecular models are commonly called

Ijjithe Brode-Hurd-Boord models (Brode and Boord

a;! 1932). Sets of balls of uniform size, with holes

>

• drilled to a uniform depth in expected bond did rections, are commercially available for building

r these models. The balls are joined by rigid rods

whose lengths are proportional to the bond

lengths. Present sets also contain flexible rods

or helical springs for making double and triple

bonds and allowing some distortion. With these

sets most molecules can be constructed. Pouleur

(1932) devised a slightly different set of models

which had two or three parallel holes in directions

of double and triple bonds. Wooster (1944) and

Wooster, McGowan, and Moore (1949) suggest

using baUs with 26 holes corresponding to the

symmetry directions in the cubic system. Brenner (1948) suggests using rubber balls instead of

rigid balls which, coupled with flexible rods, will allow the construction of more distorted models.

Sets based on all these different systems are commercially available.

6.2. Open Structure Models

The open structure models are closely related

to the open molecular models in both origin and

construction; the main difference is that these

models show the atomic positions as related to the unit cell and thus show the crystal symmetry

and the repeat unit. In general, when making

these models, much greater care must be taken in

positioning the atoms and their bond directions

than in the moecular models. Models of this type representing many known structure are available from several commercial sources. These models are usually made with wooden

balls, although plastics, cork, and recently foamed

polystyrene have been used. Holes are drilled in

these baUs in bond directions, and the balls are joined with rods of Monel, brass, or aluminum.

As these models are usually built with permanency

as an objective, iron rods are avoided because

they rust. A good general description is given

by Seymour (1938). Several devices for drilling

the holes are available and will be described under

constructional devices. Only one commercially

available set, described by Noyce (1951), is primarily designed for constructing these models.

It is quite limited in use because most crystal structures are somewhat irregular, and thus each

compound presents a special construction problem.

Several attempts to simplify the construction

of the open models have been made. Gruner (1932)

builds the wire frame first and then adds the

atoms, using Plastic Wood. Perldns (1951) uses

clay to form the atoms and, after the construction

is complete, fires the entire model to make it per- manent. The other attempts at simplification are seen in the many devices for positioning the holes

in the correct bond directions.

6.3. Open Models with Parallel Rods

Another type of open model, first described by

Sohncke (1879), consists of spheres supported on

parallel rods which are usually vertical. The rods

are rigidly mounted in a block of wood, clay,

paraffin, or foamed polystyrene, or held in place

by a wire mesh. The position of the rod in the

base corresponds to the coordinates of the atom

3
in the projection of the structure on that plane.

The sphere representing the atom may be adjusted on the rod to make its heiglit correspond with

the third coordinate. The vertical rods have no

significance in the finished model. This type of

model is very useful to crystallographers who are studying projected electron density maps.

7. Polyhedral Models

The polyhedral model consists of polyhedra,

usually of cardboard or paper, which depict the

coordination of anions around a central cation or

of bonded atoms around a central covalent atom.

The corners of the polyhedra correspond to the

positions of the surrounding atoms. The model is built up by joining appropriate corners and edges

of the polyhedra. These models have an advantage in being inexpensive to build for a class project, although they do not show the relationships inside a completed model too well, and they

do not show the positions of the central atoms.

Schneer (1952) describes their construction fairly

completely. Pauling (1939) has used these models

extensively for illustration. Quite often polyhedra have been used for certain radicals such as Si04 and SO4 in models of the vertical rod type.

They have also been used combined with molecular

models to show complex ions (Wendlandt, 1957).

The versatility of these models was emphasized

by Ashley (1930) who constructed them with ir- regular as well as regular coordination polyhedra.

Elaborate models with irregular polyhedra are rarely constructed, however, because the precise

knowledge of the coordination together with the

work of deriving the shapes of the cardboard

pieces usually justifies a model I'epresenting the

individual atomic positions.

8. Miscellaneous Types

Many miscellaneous model types have been

developed. One type closely related to the open

models is the wire model. Hughes and Taylor

(1949) describe a jig for making rigid wire molecular

representations for projection onto an electron

density map. Tilton (1958b) uses rigid wire

tetrahedra coupled with cylindi'ica.l clamps to depict network structures in silica glass. The

Dreiding wire models described by Fieser and

Fieser (1959) are commercially available. Models

based on several parallel sheets of Lucite or glass

have been used by Brown (1951), Gordon (1938),

Welch (1953), Westbrook (1957), and Wyckoff

and Ksanda (1926). The atoms are mounted on

the transparent sheets as either plastic balls,

corks, electric lamps, or painted circles. Contoured three-dimensional Fourier electron density

maps have been assembled in this manner.

Wlialen (1957) has drawn a chain of atoms on a

strip of paper which he then twisted to form an

a-helix (polypeptide chain) configuration. Lambert (1957) has used foamed polystyrene to represent molecular orbitals. Undoubtedly many other

types of models have never been described in the

literature or are discussed only in connection with

a specific problem.

9. Dynamic Models

Dynamic models have been developed primarily

to study the effect of thermal motion on atomic

arrangements. One of the early dynamic models,

described by Kettering, Shutts, and Anderson

(1930) and consisting of balls connected with

helical springs, is still commonly used in classrooms

today. Models for showing molecular vibrations

have been described by Childs and Jahn (1937)

and Trenkler (1935). Several models for stimulating the effect of thermal motion on ordered

lattices of spheres have been devised. Pohl (1952)

and Hilsch (1954) have used magnets, Woolley

and McLachlan (1949, 1950) have used lead shots

between plates, and Bragg and Nye (1947) have

used soap bubbles. Magnetic balls floating on

water have been employed by Dietzel (1956) to represent the effects of thermal motion, simulated

by blowing across the surface of the tank. There

is little doubt that the development of dynamic | models is just beginning. t

10. Construction Devices

Drilling jigs maj be separated into two groups:

those which will drill holes only in certain special

directions, and those which will drill holes in any

desired position. In the first group fall the jigs of

Wooster (1945) and Evans (1948) which will position twenty-six holes along the symmetry directions of the cubic system, that of Gibb and Bassow

(1957) which will punch tetrahedra! and octa- hedral holes in foamed polystyrene spheres, and

that of Anker (1959) which drills marked holes in rubber spheres. More elaborate devices for positioning holes in any desired direction have been

developed by Buerger (1935), Decker and Asp

(1955), and Haywood (1949), using a spherical

coordinate system to locate the bond direction,

and by Smith (1960) using bond angles.

For wire models, Hug-hes and Taylor (1958)

made a device for bending wire to conform with

bond directions.

11. References

11.1. Models in General

Bragg, W. H. and Bragg, W. L., editors (1929-30),

Stereoscopic photographs of crystal models: Adam

Hilger, Ltd., London.

Florke, W. (1955), Unterrichtsmittel zur Strukturlehre: S Der Mathematische und Naturwissenshaftliche

Unterricht 7 (8), 376-377. Gibb, T. R. P. and Winnerman, A. (1958), Chemical

geometry-application to salts: J. Chem. Ed. 35, 579

Institute of Physics, Great Britain, Report of the Crystal

Structure Model Panel of the X-ray Analysis Group.

(1947), The standardization of crystal structure models:

J. Sci. Instr. 34, 249. 4
Lipson, H. and Cochran, W. (1953), The Crystalline State Vol. Ill—The Determination of Crystal

Structures: London, G. Bell and Sons, Ltd., p. 328. Nicholson, D. G. (1952), Modeling molecules: Cbem.

Eng. News 30, 3164.

Peter, W. (1959), Modelle und Modellvorstellungen

im Chemieunterricht und ilire Grenzen: Der Mathematische und Naturwissenshaftliche Unterricht 11 (8), 353-361.

Sutton, L. E., editor, (1958) Tables of interatomic distances and configuration in molecules and ions: Burlington

House, London.

11.2. Static Models

a. Closed Molecular (Stuart Type)

Bear, Richard S. (1942), Construction of complex molecular models with applications to carbohydrates: J. Chem.

f Ed. 19, 227. Biggs, B. S. (1941), Steric hindrance in organic solids:

J. Chem. Ed. 18, 224. Black, C. E., Ill and Dole, Malcolm (1941), Molecular

models with free rotation: J. Chem. Ed. 18, 424. Bonhop, Paul, The master crystal model set: Paul Bonhop

Inc., 164 John St., New York 7, N.Y.

liBriegleb, G. (1950), Beispiel einer Basizitatsanderung

durch sterische Behinderung mesomerer Effekte- Erlautert an neu berechneten Stuart-Atomkalotten:

Z. Ang. Chem. 62, 262. Briegleb, G. (1950), Wirkungsradien von Atomen in Molekiilen (Atomkalotten und Molekiilmodelle)

Fortschr. Chem. Forsch. 1, 642. Campbell, J. A. (1948), Structural molecular models:

J. Chem. Ed. 25, 200. Caster, L. and Corey, R. B. (1958), Magnetic hydrogen

bonds for molecular models: Acta Cryst. 11, 448. Corey, R. B. and PauUng, L. (1953), Molecular models

of amino acids, peptides, and proteins: Rev. Sci. Instr. 24, 621. Fisher Scientific Co. (1939), New molecular models

conform with modern theory: Laboratory 10, 94. Fisher Scientific Co. (1959), Molecules in "3D":

Laboratory 27, 112. Godfrey, J. C. (1959), Accurate molecular models: J. Chem. Ed. 36, 140. HarreU, B. and Corwin, A. H. (1955), Models of plane

molecules: J. Chem. Ed. 32, 186. Hartley, G. S. and Robinson, C. (1952), Atomic models, Part 1—A new type of space filling atomic model:

Trans. Faraday Soc. 48, 847. Lambert, Frank L. (1953) Molecular models for lecture demonstrations in organic chemistry: J. Chem. Ed.

30, 503. Lapine, Arthur S. and Co. (1954), Atom models according

to Stuart and Briegleb for the construction of molecular models: Lanco News 6 (2) 2. Lapine, Arthur S. and Co. (1959), Atom models, LaPine

Apparatus Rev. 10, 5. Martin, J. H. (1952), Molecular model theory: Paint

Manuf. 22, 178, 376, 392. MUls, G. L. and Phillips, D. AI. P. (1950), Molecular

models: Nature 166, 1033. Minne, N. (1929), Molecular models in organic chemistry:

J. Chem. Ed. 6, 1984.

Noll, W. (1959), Concerning the structural density in

lattices: The structural density in the diamond lattice: Monatshefte Neues Jahrb. f. Mineralogie 1959(2),

34-38.

Pierce, J. B. (1959), Molecular models: J. Chem. Ed.

36, 595. Robinson, C. and Ambrose, E. J. (1952), Atomic models, Part 2—The use of atomic models in investigating stable configurations of protein chains: Trans. Faraday Soc. 48,

854. Robinson, C. (1954), Atomic models, Part 3—Some stereo- chemical problems in dyeing: Disc. Faraday Soc. 16, 125. Settatree, A., Thomas, S. L., and Yardley, V. A. (1950), Molecular models: Nature 166, 59.

Stuart, H. A. (1934a), "Molekulstruktur. Bestimmung

von Molekiilstrukturen mit physikahschen Methoden":

Julius Springer, Berlin. Stuart, H. A. (1934b), Uber neue Molekulmodelle: Z. Phys. Chem. (B) 27, 350. Stuart, H. A. (1937), Valenzwinkel und Wirkungsradius

gebundener Atome: Z. Phys. Chem. (B) 36, 155-164.

Stuart, H. A. (1944), Model experiments on fiber molecules:

Z. Elektrochem. 50, 67. Stuart, H. A. (1951), Stuart's Atomkalotten: Rec. Trav. Chim. 70, 17-18.

Stuart, H. A. (1952), Die Struktur des freien Molekiils:

Julius Springer, Berlin. Taylor, Dean, Jr. and Rutzler, J. E., Jr. (1958), Adhesion

Using molecular models: Ind. Eng. Chem. 50, 928. Taylor, H. S. (1941), Large molecules through atomic

spectacles: Proc. Am. Phil. Soc. 85, 1. Tavlor, H. S. (1942), Construction of molecular models:

U.S. Patent No. 2,308,402, Jan. 12, 1943. Wepster, B. M. (1946), Stuart's "Atomkalotten": Rec.

Trav. Chim. 65, 318. Wepster, B. M. (1951), Stuart's Atomkalotten: Rec. Trav. Chem. 70, 19.

b. Closed Packing Type

Badgley, C. D. (1945), Three dimensional models: Plastics

3, 56, 90. Barlow, W. (1884), Probable nature of the internal symmetry of crystals: Nature, 29, 186-188, 205-207. Barlow, W. (1897), A mechanical cause of homogeneity of structure and symmetry geometrically investigated; with

special application to crvstals and to chemical combination: Proc. Roy. Dublin Soc. 8 (6), 527-690. Barlow, W. and Pope, W. J. (1906), A development of the atomic theory which correlates chemical and crystalline structure and leads to a demonstration of the nature of valency: J. Chem. Soc. London 89, 1675-1744. Barlow, W. and Pope, W. J. (1907, The relation between

the crystalline form and the chemical constitution of simple inorganic substances: J. Chem. Soc. London 91, 1150-1214. Barlow, W. and Pope, W. J. (1908), On polymorphism with

especial reference to sodium nitrate and calcium carbonate: J. Chem. Soc. London 93, 1528-1564. Barlow, W. and Pope, W. J. (1910), The relation between

crystal structure and chemical composition, constitution,

and configuration of organic substances: J. Chem. Soc. London 97, 2308-2388.

Barnett, E. DeB. (1958), The face-centered cube and

cubical close-packing: J. Chem. Ed. 35, 186. Bernal, J. D. (1959), A geometrical approach to the struc- ture of liquids: Nature 183, 141. Buerger, M. J. and Butler, Robert D. (1936), A technique

for the construction of models illustrating the arrange- ment and packing of atoms in crystals: Am. Mineralogist

21, 150. Buerger, M. J. and Butler, Robert D. (1938), Data for the construction of models illustrating the arrangement

and packing of atoms in crvstals: Am. Mineralogist

23, 471. Campbell, J. A. (1957), Some simple solid state models:

J. Chem. Ed. 34, 210. Davidson, N. (1952), Cork ball experiments on crystalline

and molecular structures: J. Chem. Ed. 29, 249. Dorris, J. E., Frondel, C, et al. (1938), Atomic packing

models of some common silicate structures: Am.

Mineralogist 23, 65. Hatch, R. A., Comeforo, J. E., and Pace, N. A. (1952), Transparent, plastic-ball crystal structure models: Am.

Mineralogist 37, 58. Hauser, E. A. (1941), A simple method of building close- packed molecular and crvstal models: J. Chem. Ed.

18, 164. Heesch, H. and Laves, F. (1933), tlber diinne Kugelpackungen: Z. Krist. A85, 443-453. Kenney, M. E. (1958), Permanent packing type crvstal models: J. Chem. Ed. 35, 513.

5
Langmuir, D. B. and Nelson, R. B. (1940), Crystal struc- ture models for close-packed systems: Rev. Sci. Instr. 11, 295. Martin, S. T. (1939), On the thermionic and adsorptive

properties of the surfaces of a tungsten single crystal:

Phys. Rev. 56, 947. Nelson, R. B. and Langmiur, D. B. (1940), Crystal models

for close-packed systems: Phys. Rev. 57, 559. Ordway, Fred (1952), Transparent molecular models: Chem. Eng. News 30, 3912. Patterson, A. L. (1941), Crystal lattice models based on

the close packing of spheres: Rev. Sci. Instr. 12, 206. Sanderson, R. T. (1959), Models for demonstrating

electronegativity and "partial charge": J. Chem. Ed.

36, 507. Scattergood, A. (1937), The making of crystal lattice and

unit-cell models: J. Chem. Ed. 14, 140. Tompson, W. (Lord Kelvin) (1889), Molecular constitution of matter: Proc. Roy. Soc. Edinburgh 16, 693-724. Wear, J. I., Steckel, J E., Fried, M., and White, J. L.

(1948), Clay mineral models, construction and implications: Soil Sci. 66, 111.

c. Open Models (Molecular, Bond Type)

Bent, R. L. (1953), Aspects of isomerism and mesomerism;

J. Chem. Ed. 30, 328. Bondoc, N. R. (1942), Molecular models: J. Chem. Ed.

19, 395. Brenner, F. C. (1948), A new crystal model construction

set: J. Chem. Ed. 35, 371. Brenner, F. C. (1948), New crystal model sets aid education and research: Laboratory 18, 7. Brode, W. R. and Boord, C. E. (1932), Molecular models

in the elementary organic laboratory I: J. Chem. Ed.

9, 1774. Dewar, J. (1867), On the oxidation of phenyl alcohol, and

a mechanical arrangement adapted to illustrate struc- ture in the nonsaturated hydrocarbons: Proc. Roy. Soc. Edinburgh 6, 82. French, S. J. (1933), Adaptable electronic models: J. Chem.

Ed. 10, 564-566. Hartshorn, L. (1938), Construction of molecular models of

dielectrics: Proc. Phys. Soc. (London) 50, 852. Hazelhurst, T. H., Jr., and Neville, N. A. (1935), New

models of old molecules. Their construction and use in chemical education: J. Chem. Ed. 13, 288. Hazelhurst, T. H. (1940), Construction of molecular

models: Rept. New England Assoc. Chem. Teachers

43, 23. Kauffman, G. B. (1959), Simplified models of inorganic

stereoisomers: J. Chem. Ed. 36, 82. Le Bel, J. A. (1874), Sur les relations qui existent entre les formules atomiques des corps organiques et le pouvoir

rotatoire de leurs disolutions: Bull, de la Soc. Chim. de

Paris (2)33, 337-347. McGowan, J. C. and Moss, K. (1952), Improvements in the construction of molecular models: J. Sci. Instr. 39,

234. McGowan, J. C. and Moss, K. (1953), A method for the

construction of inexpensive molecular models: Chem.

and Ind. 73, 292. Myers, R. T. (1958), Models of metal coordination compounds: J. Chem. Ed. 35, 153. Noller, C. R. (1947), A simple apparatus to demonstrate

Walden inversion: J. Chem. Ed. 34, 277. Pasteur, L. (1848), Sur les relations qui peuvent exister entre la forme cristalline, la composition chimique et

le sens de la polarisation rotatoire: Ann. de Chim. et Phys. (3)34, 442-459.

Peterson, Q. R. (1959), Engineered fittings make true models: Chem. Eng. News 37, 108-109.

Pouleur, L. (1932), Models as a visual aid in the teaching

of chemistry, atomic and molecular structures: J. Chem. Ed. 9, 301. Subluskey, L. A. (1959), Molecular models with variable bond angles: J. Chem. Ed. 36, 26.

Tanaka, J. (1957), Inexpensive molecular models for use

in the laboratory: J. Chem. Ed. 34, 603. van't Hoff, J. H. (1874), Voorstel tot Uitbrieding der Tegenwoordig in de Schickunde gebruikte Structuur- formules in de Rosmte. Wade, I. W. (1928), Molecular models, a student project:

J. Chem. Ed. 5, 193. Wheland, G. W. (1949), Advanced organic chemistry'

196, 197, 419 (second edition) : John Wiley and Sons,

Inc., 440 Fourth Avenue, New York, N.Y.

Wooster, N., McGowan, J. C, and Moore, W. T. (1949),1 Recent developments in representing molecular struc- tures by models: J. Sci. Instr. 36, 140. Wooster, W. A. (1944), The construction of molecular models: J. Sci. Instr. 31, 125.

d. Open Models (Crystal, Bond Type)

Bennett, C. W. (1940) Home-ma.de structural atoms:' Trans. Illinois State Acad. Sci. 33, 100. Bravais, A. (1850), Memoire sur les systfemes formes par

des points distribufes reguliferement sur en plan ou dans

I'espace: J. de I'Ecole polyt. 19, 1-128. Translation! by Shaler, A. J., Cryst. Soc. Am. Memoir Number One

(1949) The Book Concern, Hancock, Michigan.

Fisher, D. J. and Stevens, E. H. (1937), Building nuclear

crystal structure models: Am. Mineralogist 33, 268. Frankenheim, M. L. (1842), Die Gesetze der Hemiedrie:

Am. d. Phys. u. Chem. 56, 275. i Gruner, J. W. (1932), A new method for building crystal structure models: Am. Mineralogist 17, 35. |i Lapine, Arthur S. and Co. (1959), Three-dimensional

crystal lattice models: LaPine Apparatus Rev. 10, 4.' Noyce, W. K. (1951), Molecular models of silicates for lecture demonstrations: J. Chem. Ed. 38, 29. Perkins, A. T. (1951), Atomic structure models for clayj minerals: J. Chem. Ed. 38, 388.

[ Seymour, K. M. (1938), A simple method of crystal

model construction: J. Chem. Ed. 15, 192.

e. Open Models (Vertical Rods)

t Bowman, H. L. (1911), Note on the construction of models

to illustrate theories of crystal structure: Mineralogical

Mag. 16, 51. Bowman, H. L. (1913), Eine Notiz uber Konstruktion von

Modellen, welche zur Illustrierung der Kristallstruktui^ dienen: Z. Krist. 53, 583. Lee, F. S. (1957), Three-dimensional flexible molecular models: Acta Cryst. 10, 485. Sander, B. (1924), A model for the illustration of spacelattices and complexes: Z. Krist. 59, 89. Schoncke, L. (1879), "Entwickelung einer Theorie dei Kristallstruktur;" Leipzig.

Spangenberg, K. (1921), A. Simple device for making

crystal structure models: Centr. Mineral. Geol., p. 229. Whitlock, H. P. (1920), Model for demonstrating crystal structure: Am. J. Sci. 49, 259.

f. Polyhedral Models

Ashley, R. H. (1930), The making and use of tetrahedra models: J. Chem. Ed. 7, 2904. Entriken, J. B. (1932), A new type of atomic model for organic chemistry: J. Chem. Ed. 9^, 2081. Pauling, L. (1939), Nature of the chemical bond: Cornell University Press, pp. 380-400. Robey, R. F. (1935), Molecular models in inorganic

chemistry: J. Chem. Ed. 13, 378. Schneer, C. J. (1952), Coordination Models: Am. Mineralogist 37, 223.

Tilton, L. W. (1957), Noncrystal ionic model for silica glass: J. Research NBS 59, 139 (RP2782).

Tilton, L. W. (1958), Role of vitrons in alkali silicate binary glasses: J. Research NBS 60, 351 (RP2854).

Tilton, L. W. (1958), The vitron: NBS Tech. News BullJ

43, 236. 6
Wendlandt, W. W. (1957), Magnetic model for complex

ions and molecules: J. Chem. Ed. 34, 223.

J jZoltai, Tibor (1959), Simple technique for the construction

of polyhedral structure models: Am. Mineralogist 44,

1311-i3.

g. Miscellaneous Model Types

am

Blank, H. R. (1945), A method for the construction of crystal models: Rocks and ^Minerals 30, 583. Brown, W. (1941), The atomic arrangement in the sulphur

unit cell: J. Chem. Ed. 18, 182. Farmer, W. (1881), Apparatus for teaching chemistry:

U.S. Patent 242,821, June 14, 1881.

Fieser, L. F. and Fieser, M. (l959), Steroids, Reinhold

Publishing Corp., 330 West 42d St., New York 18, N.Y.

Fowles, G. W. A. (1955), Orbital models: J. Chem. Ed. 32,

260. Gordon, S. G. (1938), Making structure models [Abstract]: Am. Mineralogist 23, 170. Hazlehurst, J. H., Jr. (1940), Pictures of acid-base reactions: J. Chem. Ed. 17, 374. Holness, H. (1943), Electronics—Some teaching models:

School Sci. Rev. 25, 38. Kwiecifiski, A. (1950), Crystal lattices of the element

carbon: Przeglad Gorniczy 6, 587. Lambert, F. L. (1957), Atomic and molecular orbital models: J. Chem. Ed. 34, 217. Pearson, R. G. (1959), How to make orbitals: Chem. Eng.

News 37, 108. Sanderson, R. T. (1958), A schematic representation of valence: J. Chem. Ed. 35, 541. Sanderson, R. T. (1957), New molecular models showing

distribution and bond polarity: J. Chem. Ed. 34, 195. Welch, A. J. E. (1953), A three-dimensional coordinate

model for demonstration of inorganic crystal structures: Acta Cryst. 6, 476. Westbrook, J. H. and DeVries, R. C. (1957), A new type

of crystal model: J. Chem. Ed. 34, 220. Whalen, T. A. (1957), Model of the alpha helix configuration in polypeptides: J. Chem. Ed. 34, 136. WyckofF, R.'W. G. and Ksanda, C. J. (1926), A simple

model for illustrating the atomic arrangements in

crystals: Am. J. Sci. 11, 377.

Zinsser, H. H. (1954), A rapid method for the assembly of semidiagrammatic molecular models: J. Chem. Ed. 31,

662. 11.3. Dynamic Models

Andrade, E. N. (1949), A latern model to illustrate dis- locations in crystal structure: Proc. Phys. Soc. 62A,

394. Andrews, D. H. (1931), Chemical applications of Raman

spectra: J. Chem. Ed. 8, 1133. Bragg, W. L. and Lomer, W. M. (1949), A dynamical

model of a crystal structure II: Proc. Roy. Soc. A196,

171. Bragg, W. L. and Nye, J. F. (1947), Dynamic model of a

crystal structure: Naturwissenschaften 34, 328. Bragg, W. L., and Nye, J. F. (1947), A dynamic model of a crystal structure: Proc. Roy. Soc. (London) A190,

474."

Childs, W. H. J. and Jahn, H. A. (1937), A simple demonstration model of a vibrating molecule: J. Sci. Instr. 14, 141.

Conway, B. E. (1954), A magnetic model of polyelectrolyte

interaction: J. Chem. Ed. 31, 477.

Dietzel, A. A. (1956), The structure of glass [motion

picture]: The Max Planck Institute for Silicate Research, Berlin. Hilsch, R. (1954), Ein Kristallgittermodell: Z. Physik

138, 432. Kenney, M. E. and Skinner, S. M. (1959), Hollow lantern

slides illustrating crystal structure: J. Chem. Ed. 36,

495. Kettering, C. F., Shutts, L. W., and Andrews, D. H.

(1930), A representation of the dynamic properties of molecules by mechanical models: Phys. Rev. 36, 531. Lomer, W. M. (1949), A dynamical model of a crystal structure III: Proc. Roy. Soc. (London) A196, 182. Morrell, W. E. and Hildebrand, J. H. (1936), The dis- tribution of molecules in a model liquid: J. Chem.

Phys. 4, 224. Pohl, R. W. (1952), Die Bedeutung von Kristallbaufehlern

fiir die Physik fester Korper: Naturwissenschaften 39, 9. Smith, C. S. (1949), Blowing bubbles for Bragg's dynamic

crystal model: J. Appl. Phys. 20, 631. Trenkler, F. (1935), Eigenschwingungen mechanischer

Molekiilmodelle: Phys. Zeits. 36, 162. Woolley, R. H. and McLachlan, Dan, Jr. (1949), A two

dimensional model illustrating the effect of thermal

agitation during the deformation of metallic solids: Bui. Univ. Utah 39, (18), Bull. No. 42. Woolley, R. H. and McLachlan, Dan, Jr. (1950), A model

illustrating the effect of thermal agitation: J. Chem.

Ed. 27, 187.

11.4. Construction Devices

Anker, R. M. (1959), Construction of molecular models:

J. Chem. Ed 36, 138. Buerger, M. J. (1935), A device for drilling holes in spheres

required in the construction of crystal structure models: Rev. Sci. Inst. 6, 412. Decker, B. F. and Asp, R. T. (1955), A jig for making

atomic models: J. Chem. Ed. 35, 75. Dore, W. H. (1926), A device for constructing models of carbon compounds: J. Chem. Ed. 3, 319. Evans, R. C. (1948), A jig for the preparation of balls for the construction of crystal structure models: Rev.

Sci. Inst. 19, 402. Gibb, T. R. P., Jr. and Bassow, H. (1957), Construction

of crystal models from styrofoam spheres: J. Chem.

Ed. 34, 99. Haywood, C. A. (1949), A simple universal jig for the

construction of crystal models: J. Sci. Instr. 26, 379. Hughes, W. and Taylor, C. A. (1958), Jigs for making

crystallographic wire models: J. Sci. Instr. 35, 261. Smith, D. K. (1960), A simple centering jig and goniometer

for punching or drilling spheres for structure models: Am. Mineralogist 45. Terpstra, P. (1939), Wooden balls for structure models: Natuurw. Tijdschr. (Belg) 21, 284. Wooster, W. A. (1945), A spherical template for drilling balls for crystal structure models: J. Sci. Instr. 22, 130.

Washington, B.C., December 15, 1959.

U.S. GOVERNMENT PRINTING OFFICE: 19S0

7

THE NATIONAL BUREAU OF STANDARDS

I The scope of activities of the National Bureau of Standards at its major laboratories, in Washington,

i D.C., and Boulder, Colo., is suggested in the following listing of the divisions and sections engaged

in technical work. In general, each section carries out speciaUzed research, development, and engiI neering in the field indicated by its title. A brief description of the activities, and of the resultant

; publications, appears on the inside front cover. WASHINGTON, D.C.

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