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To determine if any factors are associated with knee stiffness after total knee arthroplasty (TKA), we retrospectively reviewed the medical records and radiographs of patients who had knee manipulation after total knee replacement at ScottWhite Memorial Hospital from 1983 to 1993. Twenty-five patients who had knee manipulation after TKA were matched by surgeon, year of surgery, and age (+/- 5 years) with a study group of 25 patients who did not have knee manipulation after TKA. Patients in the manipulated group had decreased flexion at the time of discharge from the hospital after the knee arthroplasty and a decreased final flexion. The age of the patient, time from surgery to manipulation, and preoperative flexion did not correlate with final flexion attained in the manipulated group. Relative to the control study group, the manipulated group had an increase in postoperative anteroposterior femoral thickness. A decrease in patellar height was noted both in the manipulated group and in the control nonmanipulated group. There was no significant difference between groups for a change in patellar height.

Thirty patients had 32 cementless total hip arthroplasty revisions and were evaluated postoperatively for clinical function (Harris Hip Score) and radiographic evidence of implant stability. Of the 26 femoral components revised, 16 were revised with anatomic long-stem femoral prostheses, and 10 were revised with straight mid-stem-length components. All components were collared and had circumferential proximal fiber-mesh porous coating. Seven of 16 patients had radiographic subsidence after revision with long-stem components (2 to 30 mm); 6 of 10 patients had subsidence after revision with mid-stem femoral components (2 to 25 mm). Of the 13 patients with femoral subsidence, 8 had calcar reconstruction with allograft bone; of the 13 patients without radiographic subsidence, 8 did not require calcar reconstruction. One of 27 fiber-mesh, porous-coated acetabular components migrated (30 mm). No components have been removed or revised. Even with circumferential proximal porous coating, femoral implant stability remains unpredictable in total hip arthroplasty revision.

Using a neodymium glass laser and time-synchronized pulse detection, second harmonic signals were observed from a number of clay mineral powders. The second harmonic generation (SHG) experiments provide the first physical evidence (other than diffraction patterns) for the polar nature of the kaolinite layer and its stacking sequences. Well-crystallized nacrite and dickite specimens gave signals comparable to those of quartz, but the SHG intensities from the smaller kaolinite and halloysite crystallites were noticeably weaker. Based on results from eight specimens, there appears to be a direct correlation between SHG intensity and particle size, similar to that reported previously for quartz.

The basal spacings of montmorillonites with Li, Na, K, Cs, Mg, Ca, Sr, Ba, and Pb interlayer cations were measured after immersion in dimethylsulfoxide (DMSO) and in water-DMSO mixtures. In DMSO alone, the spacings were in the range 18.3–19.3 A and fell on or near a single curve when plotted against ionic field strength, q/r2, where q = valence and r = ionic radius. These spacings correspond to double layers of DMSO molecules between the silicate layers. Water had practically no effect on the spacings when the mole fraction of DMSO exceeded about 35–45%. Osmotic swelling of Li-, Na-, and K-mont-morillonite occurred up to mole percentages of DMSO 45%, 30%, and 10%, respectively. K- and Cs-mont-morillonite formed single-layer complexes in appropriate water-DMSO mixtures with spacings of 14.3 A prior to development of double-layer complexes when the mole fraction of DMSO exceeded 35% and 15%, respectively.

Lattice spacings of layer silicates, particularly clay minerals, may exceed 20 A. The errors in measuring lattice spacings increase rapidly for spacings greater than about 10 A and diffraction angles 20 tess than about 10 ~ Long-chain organic compounds, such as normal alcohols, ClcC2o, and normal alkancs (paraffins), Cz6-C3o, provide useful calibrations for lattice spacings in the range 10-50 A. The basal spacings of the calibrating substances are determined from their higher order reflections in the angu- lar range where reflections from quartz and silicon are used as standards. INTRODU(.qI'ION

Nickel nitrate solution is potentiometdcally titrated (a) with montmorillonite, (b) without montmorillonite, in the nitrate solution. X-ray powder diffraction and chemical analyses are made of the products formed by the clay at various stages of titration. The pH values of the titration curve (a) are lower than those of curve (b) until the brucite-like hydroxy- nickel interlayer is more or less complete. The resulting product then closely resembles a chlorite. The preferential pre- cipitation of hydroxide in the interlayer region is explained in terms of the acidic character of montmorillonite interlayers.

Uranyl acetatye solutions, ranging in concentration from about 100 ppm to 3700 ppm, were re-acted with the Na-, K-, and Ca- forms of zeolite A. The crystalline products from the Na- and K-A zeolites resembled compreignacite (K2O·6UO3·11H2O) and from the Ca-A, becquerelite (CaO·6UO3·11H2O). With higher concentrations of uranyl acetate, only X-ray-amorphous products were obtained. The compreignacite-like products gave sharp X-ray powder diffraction patterns and were indexed with orthorhombic, quasi-hexagonal unit cells which showed a significant variation of the axial ratio b/a from values just greater than, to values just less than √3. The becquerelite-like phase was always accompanied by unreacted zeolite. Compreignacite was synthesized from uranyl acetate and KOH solutions at room temperature over a period of several days.

SummaryKerolites from Goles Mountain (Yugoslavia), Wiry (Poland), Madison Co. (North Carolina), and Kremze (Czechoslovakia) are compared with talc and stevensite. Chemical analyses give a composition for kerolite near R3Si4O10(OH)2.nH2O with R mainly Mg and n about 0·8–1·2. Infra-red data and dehydration-rehydration experiments suggest that the additional water is partly surface-held hydrogen-bonded molecular water, lost up to about 300 °C and easily recoverable, and ‘water’ held as surface hydroxyls, lost at temperatures up to about 650 °C and less easily recoverable. The surface area of kerolite from North Carolina by nitrogen absorption measurements is 196 m2/g.X-ray data show broad basal reflections, a basal spacing (after Lorentz-polarization correction) of about 9·6 Å and a crystallite size of about five structural layers, which is consistent with the large surface area. Two-dimensional hk bands indicate a randomly stacked layer structure with b ≈ 9·14 Å and a crystallite ‘diameter’ of about 150 Å. The basal spacing shows no expansion in water and no thermal contraction up to 500°C. A partial and irregular swelling with ethylene glycol is obtained only after prolonged cxposure (several weeks). In both respects, kerolites differ from stevensite. Kerolites come close to talc in structure and composition but differ in having a highly random layer arrangement, a slightly enlarged basal spacing, which could be due to misfit of layers caused by random stacking, and weaker interlayer bonding.Kerolite is considered to be a useful varietal name for this talc-like mineral in agreement with the views of D'yakonov and of Maksimovic. It cannot be defined as serpentine + stevensite.

SummaryAn X-ray and chemical examination of deweylites reveals that they are intimate mixtures of very poorly ordered trioctahedral 2:1 and 1:1 layer silicates. The 2:1 mineral exhibits no swelling in the presence of ethylene glycol or water and is best described as an extremely fine-grained and highly disordered form of talc, for which the term kerolite is often used. Stevensite is not a component of deweylites. The 1:1 component most closely resembles a disordered chrysotile.Evaluation of the chemical data, including values for H2O +, shows that both end-members are hydrated to various degrees. This hydration is most probably attributable to the presence of water molecules and hydroxyls associated with the large surface areas and unbalanced surface bonds. Formulae for the end-members are approximately R3Si4O10(OH)2·0·3 0·7 H2O and R3Si2O3(OH)4·0·3–0·7 H2O where R is principally Mg, but samples with more or less H2O are entirely possible due to variations in crystallinity. No specific formula can be given to deweylites as they are mixtures with variable proportions of the components. The name is useful, however, as a field or ‘box’ term, similar to the use of garnierite and limonite.

The a and c unit cell parameters of M(OH)2, brucite-like structures with M=Mg, Ni, Co, Fe, Mn, Cd, and Ca, are considered in relation to M-O distances taken as the sum of the ionic radii, MVI and OIV. The a parameters are related to (M-O) by flattening of the octahedral coordination groups, with a flattening angle α=97.4±0.4°. The c parameters are divided into the octahedral layer thickness, h(oct), and the interlayer spacing h(inter). The latter is related to the (O-H) distances, which decrease as (M-O) increases. Infrared v(O-H) stretching frequencies vary with (M-O) in the same manner as h(inter) varies with (M-O). The values of v(O-H) decrease as h(inter) decreases and the atomic weight of the cations increases. The results are consistent with previous data for cation-substituted talcs. It is suggested that the M2+ ions associated with the O2− ions modify the reduced mass of the O-H vibrations so that v(O-H) decreases with increasing mass of M.

Chloride-, sulfate-, and perchlorate-exchanged forms of hydrotalcite have been prepared and their layer spacings determined after equilibration in hydrous atmospheres and after heat-treatments up to the temperature of decomposition in the range 300–400°C. The initial carbonate form of hydrotalcite and also brucite, for purposes of comparison, have been similarly studied. Only chloride-hydrotalcite and brucke exhibit a single phase stable to the decomposition temperature. The other anionic forms exhibit various phases with different layer spacings which are interpreted in terms of the size, orientation, and stability of the anions and, in some cases, the presence of additional water. A regularly interstratified form of sulfate-hydrotalcite (layer spacing = 19.80 A) is obtained at room temperature and relative humidity

Hydroxy-Al- and hydroxy-Mg-montmorillonite were prepared by treating dispersed Na-montmorillonite with aluminum and magnesium nitrate solutions and titrating with NaOH solutions so that the OH/A1 ratio varied from zero to 3.0 and the OH/Mg ratio from zero to 2.0. External precipitation of Al and Mg hydroxides was observed when the OH/M ratios (M = metal) approached 3 and 2, respectively. From chemical analyses of the initial Na-montmorillonite and the hydroxy-metal montmorillonites, structural formulae were derived by assuming that the silicate layer compositions remained unchanged. Prior to the addition of NaOH, the average interlayer material approximated in composition to [Al(OH)2]+ and [Mg(OH)]+. With additions of NaOH the interlayer compositions moved progressively towards Al(OH)3 and Mg(OH)2. When the hydroxy interlayers approached completion, external precipitation was observed. X-ray powder diffraction data showed that the hydroxy-Mg products have less tendency to swell in ethylene glycol and water, and greater thermal stability than the hydroxy-Al products. Initially, when the average interlayer compositions were near Al(OH)2 and Mg(OH), swelling followed more nearly the normal behavior.

Progress in science is not a linear function of time but resembles more closely a sigmoidal process in which new trends depend on the nucleation of new ideas and the re-activation of older studies. New and improved instruments, particularly electron microscopes and microprobes, infrared spectrometers and atomic absorption analysers have been the nucleating agents for many new lines of investigation. The interdisciplinary nature of clay mineralogy makes communication between different areas of study very important and the clay mineral societies have an important part to play in this respect.In the future, renewed efforts to obtain a convenient and reliable method of quantitative mineral analysis are likely to be made. Crystal structure analysis will be directed increasingly towards the study of order and disorder in cation distributions, layer charges, and layer stacking arrangements. Studies of domain structures in layer silicates will continue, and further refinements in mixed-layer structure analysis can be expected. Infrared spectroscopic analysis will increasingly become a major tool. The study of clay mineral synthesis and alteration in nature and in the laboratory shows signs of important re-activation. Clay-organic studies are developing in many directions.

Hydroxy-aluminium beidellites are prepared by treating Na-saturated beidellites from Taiwan, with compositions intermediate between end-member beidellite and end-member montmorillonite, with hydroxy-aluminium solutions having OH/Al ratios mainly between 2·00 and 2·50. Chemical analyses show that hydroxy-aluminium ions have compositions near Al6(OH,O)16 and charges near 1·0 in two cases, and near 2·2 in a third case. The basal spacing of the prepared clays is near 17 Å and remains without collapse up to 500°C. Argon adsorption measurements at liquid nitrogen temperatures, after heat-treatment up to 325°C in vacuo overnight, give surface areas near 500 m2/g when the exchangeable Na ions are about one-third replaced by hydroxy-aluminium, but near 200 m2/g when wholly replaced by hydroxy-aluminium. In the latter case the hydroxy-aluminium covers the internal surfaces of the clay almost completely prior to the heat-treatment.

A suite of Georgia kaolinites, ranging from well-ordered to very poorly ordered samples, were studied to explore correlations between degree of structural disorder, geological environment, Fe3+ content, Fe3+ electron paramagnetic resonance (EPR) spectrum, and infrared (IR) hydroxyl-stretching band frequencies and bandwidths. Samples from different localities showed a wide range of disorder which appears to be related to differences in their geological environments. High iron content correlated strongly with low degree of order. The areas of both the I and E components of the EPR spectrum and the fractional I area correlated inversely with degree of order. Fourier-transform IR studies of kaolinites and dickites showed that (1) interlayer hydrogen bonding is weaker in dickite than in kaolinite; (2) frequency of the ν1 stretching band of the inner-surface hydroxyls increases sequentially from well-ordered kaolinite through the disordered structures to well-ordered dickite, which is consistent with a model for disorder based on vacancy displacement; and (3) the character and temperature dependence of the inner hydroxyl-stretching band is not compatible with the crystal structures of kaolinite and dickite as refined by Suitch and Young.

Nickel ions play similar roles to magnesium ions in nickel-containing hydrous layer silicates. The extent of the replacement of Mg by Ni ranges from small proportions to complete, or almost complete, replacement. Particular interest attaches to the micro-crystalline, clay grade, minerals formed by processes of lateritic weathering. The multiplicity of names proposed in pre-X-ray-diffraction times must be re-evaluated in terms of modern identification procedures. Many of these minerals can now be placed in series such as:Garnierite is now used mainly as a field term, prior to more specific identification, and terms such as 7 Å- and 10 Å-garnierite are useful when identification can proceed no further than recognition of basal spacings. Further study is required of schuchardtite, and of nickel-containing smectites and sepiolites. Consideration also must be given to the composition ranges of the end-member names.

Beidellite clays near Chang-yuan, 80 km south of Hwalien, form vein-like bodies 5-10 m wide and 20-45 m deep. Andesitic rocks have been fractured by faulting permitting hydrothermal solutions to percolate and produce an altered mineral assemblage in which beidellite is associated with a mixed-layer illite-smectite, kaolinite, dusty pyrite, microquartz, cristobalite, calcite and dolomite, plagioclase, and gypsum. Ca-clay is common on outcrops and subsurface, where the clay is leached, Na-clay is found; some outcrops are partly kaolinized. Chemical analyses of the beidellite show that the structure is charged predominantly in the tetrahedral sheets. Exchange capacities are mainly in the range 120-140 mEq/100 g clay (110°C); exchangeable cations are Na ≫ Ca ≃ Mg > K. After K saturation and heating, ten samples still expand to near 17 A with ethylene glycol, but the two samples with the highest tetrahedral charge expand only to 14·6-15·0 Å although their total charge is similar to the other samples.

Wyoming montmorillonite

SummaryMotukoreaite resembles hydrotalcite and has positively charged brucite-like layers separated by carbonate and sulphate anions and water molecules. Four phases are recognized. Phase I, the normal mineral with an 11.1 Å basal spacing, readily changes to a mixture of phase I and a partially dehydrated phase II. Phase III with a basal spacing 8.7 Å persists from 50–170°C. Phase II is a pseudo-regular interstratification of phases I and III, with a spacing 11.1 + 8.7 = 19.8 Å; second- and third-order reflections are observed. Phase IV with a 7.5 Å spacing is obtained by treating motukoreaite with sodium carbonate solution to replace SO4 by CO3 anions. Motukoreaite itself shows only slight tendency to transform to a 7.5 Å phase by heat-treatment alone. Comparison is made with the mineral carrboydite, a NiAl sulphate carbonate hydrate. The possibility is considered that sulphate anions may substitute partially in the brucite-like layers to compensate for a deficiency of hydroxyl ions.

Basal X-ray peaks from normal and ethylene glycol-saturated tarasovite have been measured to 0.0.36 and 0.0.38, respectively; the mean basal spacings were 43·73 ± 0·44 and 46·05 ± 0·33 Å, with CV values of 1·31 and 0·97. The spacings indicate a near approach to a 3 : 1 illite-smectite but the CV values indicate a greater variability than is normally consistent with the allocation of a special name. Comparison of the observed spacings with those for illite showed that the more deviant values were always adjacent to positions of illite reflections. A modified Mering treatment of diffraction by mixed-layer sequences was used to estimate the proportion of illite layers; the average result was 79·9 ± 2·0%. The mineral is considered to have 3 : 1 illite-smectite units with randomly added illite layers, bringing the ratio from 75% for the ideally ordered sequence to near 80%.

SummaryThe composition of scarbroite, written in the form Al5(OH)13CO3·5H2O, suggests close crystal-chemical relations to gibbsite and to hydrotalcite and kindred minerals. Parametral relations a(S) ≃ 2b(G) and 3b(S) ≃ 5a(G), S = scarbroite, G = gibbsite, are obtained and are consistent with a hydroxy Al layer structure and interlayer carbonate anions and water molecules. Thermal transformations show two discrete hydrated phases with layer spacings near 8.5 and 7.65 Å and a third phase with initial spacing 6.65 Å which decreases progressively to 5.5 Å over the temperature range 100°–250 °C as decomposition proceeds. No clear break is observed between dehydroxylation and decarbonation.

A golden-colored, flaky mineral from Morro do Niquel, Minas Gerais, Brazil, gives an X-ray diffraction pattern of a IIb chlorite polytype, with basal spacing 14·21 ± 0·02 A and b = 9·23 A. Thermogravimetric analysis shows a progressive weight (water) loss up to 500°C, followed by a rapid weight loss corresponding to dehydroxylation of the interlayer material and a slower weight loss due to dehydroxylation of the 2:1 layer. The structural formula derived from the chemical analysis on the basis of O10 (OH)8, or total cation valence of +28, shows 5·3 total octahedral cations, i.e. probably 2·3 in the interlayers where normally 3 cations are found. This deficiency together with the appreciable loss of water below 500°C suggests a partially vermiculitized interlayer. A new method for deriving the interlayer composition gives R1·67(OH)4·08(H2O)0·59, and a ratio (OH + H2O)/R = 2·80, which approaches that of a dioctahedral interlayer and is consistent with a predominance of R3+ ions. The mineral may resemble the golden, vermiculitized biotite described by Walker and others.

Dickites with well-ordered crystal structures and with relatively high dehydroxylation temperatures develop a 14 Å phase when heated to temperatures in the range 550–800°C. The actual spacing is close to 13·7–13·8 Å. Dickites with less well-ordered structures and with lower dehydration temperatures give less development of this phase or none at all. Other kaolinite group minerals do not produce a similar phase. Thermal weight-change and differential thermal analysis data show that the 14 Å phase develops to a maximum as hydroxyl ions are eliminated from the dickite structure and infrared spectroscopic data are consistent with this result. AIKα fluorescence wavelength measurements indicate that the Al ions are in four-fold coordination in the 14 Å phase. Absence of other diffraction data makes structure analysis impossible. The description ‘chlorite-like’ for the 14 Å phase is of questionable validity.

Abstraet--Hydrothermal alteration products of serpentinite near Takovo, Yugoslavia, were studied by X-ray powder diffraction and chemical analysis. A zone of mainly blue clays adjacent to the hydrothermal vein contains intimately associated chromium kaolinite and tosudite at higher hypsometric levels and chromium halloysite(10/~) form at lower levels. A second zone of green clays contains principally illite/smectites, with predominantly illite layers nearer the first zone and smectite layers at greater distances. The potassium content diminishes as the proportion of illite layers diminishes. The composition of the smectite layers in the illite/smectite with the least proportion of illite is shown to be beidellitic. The mineralogical and chemical changes across the zone of alteration are interpreted in terms of two stages of alteration in which the second is more acidic than the first and is responsible for the inner zone of chromium-bearing kaolinite and tosudite and chromium halloysite. Key Words--Cr-halloysite, Cr-illite/smectite, Cr-kaolinite, Cr-tosudite, Hydrothermal, Serpentinite.

In a previous paper (Brindley, 1951) chamosites from a number of localities were examined, and their structure was shown to be of kaolin-type. Furthermore, it was shown that many of the variations in X-ray powder diagrams of chamosites can be accounted for by the existence of two kaolin-type structures, one hexagonal and one monoclinic, with simply related ceil dimensions.

When dehydroxylation of kaolinite powder is carried out in the usual way, the linear relations anticipated for first-order kinetics and for the Arrhenius plot of log k versus 1/T are satisfied only very approximately. Factors relating to the form of the specimen, (shape, size, compaction, container, etc.) are shown to be very important. A method is developed for obtaining data for a specimen in the form of an infinitely thin disc. The first-order kinetic relation and the Arrhenius relation are then linear, and the latter gives an activation energy of 65 K cal./mol. The dehydroxylation process is shown by x-ray analysis to proceed crystal by crystal and this leads to an interpretation of the first-order kinetics. The x-ray method is used to study the distribution of reacted and unreacted material throughout a disc of material. Although isothermal conditions are employed, large differences are found between the interior and exterior of a partially dehydroxylated disc. These effects are attributed to the influence of a water vapor atmosphere within the heated disc.

The hydration of magnesiowustite, both ferrous and ferric types, containing 5 atom % iron was measured under identical conditions as in part 2 for MgO. Iron oxides in solid solution in MgO cause initial nucleation of the reaction to be greatly protracted. However, the remainder of the reaction for magnesiowustites of similar particle size follows reaction kinetics similar to those for MgO with respect to temperature and water vapour pressure. Activation energies for stoichiometric (i.e., ferrous), and non-stoichiometric (i.e., mainly ferric) magnesiowustites are 14.4 and 20.4 kcal/mole respectively. A “quasi-solution” mechanism is suggested for the hydration reaction of MgO and magnesiowustite governed by phase-boundary reaction kinetics. The progress of the phase-boundary reaction may be directly influenced by the effects of Fe2+ and Fe3+ on the MgO lattice.

Previous studies of the kinetics of dehydroxylation of kaolinite and halloysite point to first-order reactions, in approximate conformity with the Arrhenius relation. Isothermal weight-loss measurements have shown that the rate constants are markedly dependent on factors such as specimen size, shape, and compaction. A technique has been developed for determining the reaction kinetics of infinitely thin disk-type specimens. The reactions are then strictly first order and the Arrhenius relation is obeyed. Activation energies of 65 and 55 kcal. per mole are obtained for kaolinite and halloysite, respectively. Comparison is made between the behavior of kaolinite and halloysite on the one hand and of macrocrystalline anauxite on the other. For anauxite, nucleation and growth of nuclei produce a sigmoid-type reaction curve, but for the fine-grained minerals it is believed that nucleation alone is the rate-controlling process. The dependence of the reaction rate on geometrical factors is attributed to the retention of water vapor within the powder specimen. The influence of water vapor on these reactions is discussed generally.

A possible structure for kaolinite was first put forward by Pauling (1930) in a paper dealing generally with the structures of layer-type minerals, chlorites, micas, &c. He suggested that the structure consisted of a sheet of Si–O tetrahedra arranged in a hexagonal network with a superposed sheet of Al–(O,OH) octahedra, the two together forming a layer of composition Al2Si2O5(OH)4 (fig. 2). Ross and Kerr (1931), from a detailed microscopic study of the kaolin minerals, concluded that the symmetry of kaolinite is ‘probably monoclinic’. The first attempt at a detailed structure analysis was made by Gruner (1932a) from X-ray powder photographs. The reflections, some 40 altogether, were indexed on the basis of a monoclinic cell with a 5·14, b 8·90, c 14·51Å., β 100° 12′.

Measurements of the intensities of X-ray reflections from filed and chemically prepared specimens of rhodium powder are made relatively to each other and are then converted to absolute units by comparison with suitable aluminium reflections. The scattering factors, fT, obtained experimentally for both types of powder agree satisfactorily for the higher order reflections, with a theoretically estimated scattering factor, but for the lower order reflections the experimental values are markedly low, which suggests the existence of appreciable primary extinction. Detailed calculation shows that the variation of [fT(filed)/fT(chem.)] with (sin θ)/λ can be accounted for almost entirely in terms of primary extinction, and that there is very little residual effect due to lattice-distortion of the kind found in similar experiments with copper and nickel. Measurements of the widths of the reflections are made for both types of powder; for the filed powder a total of 23 reflections for five radiations are measured. The results are discussed in relation to various theories of the nature of lattice distortion produced in metals by cold-work. The results are shown to be incompatible with the view that the broadening is due to smallness of crystal-size since the observed widths when plotted against theta fall on or near a mean curve, whereas with small crystal broadening there should be a separation according to wave-length. The difficulties attendant on any explanation in terms of periodic or semiperiodic lattice-distortion which have been discussed by Boas are briefly outlined. It is shown that the observed results may be explained in terms of a variation of the lattice spacing about the normal mean value due to the stresses caused by the filing process. Assuming a Gaussian distribution for the variation (δa/a), the spread of the distribution is calculated. In this calculation there is only one adjustable parameter and this fixes the spread of the distribution. From this distribution a calculation is made of the internal energy of the worked metal.

A white clay from the Jatoba talc mine, Castro, Parami, Brazil, is shown by chemical analysis, X-ray and electron diffraction, and by thermal analysis to be essentially pure antigorite in the strict sense of the term. Single crystal electron diffraction patterns give various values for the long a parameter, with 43.5 A perhaps the most commonly occurring, b = 9.25 .~, d(001) = 7.25 ~,. X-ray powder diffraction gives d(001) = 7.26 ,~ and b = 9.23 A. Electron micrographs show irregular platy and lath-like crystals of about 0.5-2 # size with large development of (001) planes and with b in the direction of elongation. Other crystals are observed with very unusual forms, some having holes through them. They show mainly Okl diffraction patterns and lie with the basal (001) planes normal to the stage of the instrument. The chemical analysis agrees closely with the ideal serpentine composition and the differential thermal analysis curve is consistent with antigorite.

X-ray powder data show an ortho-hexagonal cell containing two structural layers. Close similarity with the data for amesite suggests a similar disposition of the layers within the unit cell. Evidence for a superlattice parameter is obtained indicating a structure similar to that discussed by Aruja and by Onsager.

Li-, Na-, K- and Ca-saturated Wyoming montmorillonites have been prepared and used to obtain Li.Na-, Li,K-, and Li,Ca-montmorillonites with a range of Li contents. These were heated at 220°C for 24 hr, causing the Li+ ions to migrate mainly into the layer structure and leaving varying amounts of Li+, Na+, K+, and Ca2+ ions in the interlayer positions as determined by exchange with NH4+ ions. The results are only partially consistent with a migration of the Li+ ions into vacant octahedral sites up to the limit of the octahedral layer charge. Solvation of the resulting clays with water and various organic liquids showed the following results: With water, acetone and 3-pentanone, expansion of the montmorillonites increased in a step-wise manner with increasing numbers of interlayer cations qualitatively in accord with the field strength of the cations and the dipole moments of the molecules. With ethanol, ethylene glycol and morpholine, swelling with each liquid was practically independent of the number of interlayer cations, within the limits of the prepared materials. It is suggested that for the second group of liquids some mechanism additional to cation-dipole interactions, such as hydrogen bonding to silicate oxygen surfaces, may play an important part.

A 2–20 µ fraction of phlogopite has been converted to the sodium form by use of sodium tetraphenylboron-NaCl solutions. The cation exchange capacity of the treated material increases to a maximum of about 212 m-eq/100 g, which agrees well with the K2O + Na2O content of the initial mineral. Li-, Na-, Ca-, and Mg-saturated forms have been prepared and examined by X-ray diffraction and by thernogravimetric measurements in air, in vacuo, and at progressively elevated temperatures. Hydration states corresponding to double water layers are observed for the Mg- and Ca- forms, and to single water layers for the Mg-, Ca-, Na-, and Li- forms. The numbers of water molecules per unit cell and per interlayer cation are considered for the various hydration states.

Complexes are formed between a Ca-saturated fluorhectorite and organic molecules derived from propane by substituting benzene, pyridine, and piperidine rings in the 1,3 positions. The complexes are mainly of the A- and B-types described earlier by Greene-Kelly. Only one of the substances studied forms long-spacing complexes; in this case, the organic molecule is terminated at one end by a benzene ring and at the other by an active =NH group. Neutral forms of this molecule develop double-layer complexes, cationic forms develop single-layer complexes. The results are consistent with data for alcohols, alkyl chlorides and bromides, and alkyl amines.

Many solid state reactions can be represented by equations of the type F(α) =kt, where α is the fraction of material reacted in time, t. These equations can be expressed in the form F(α) =A(t/t0.5) where t0.5 is the time for 50% reaction and A is a calculable constant depending on the form of F(α). Numerical tables are given of F(α) in relation to α, and to (t/t0.5), for nine equations corresponding to reactions which are diffusion controlled, or are reaction-rate controlled, or obey first order kinetics, or follow the equations of Avrami and Erofe'ev. The application of the tables to the analysis of experimental data is described.

Clays containing kaolinite, diaspore, and boehmite are analyzed chemically and mineralogically and their high-temperature reactions in the range 1000° to 1500°C are followed quantitatively by X-ray diffraction measurements. It is shown that the development of mullite progresses toward the equilibrium value as the temperature approaches 1500°C. When considered in detail, the reactions reflect the source of the alumina. Diaspore and boehmite first form corundum at widely different temperatures which results in the reactivity of the corundum from boehmite being greater than that from diaspore, and, in consequence, mullite develops more readily from the boehmite-containing clays. Relative expansions of clays rich in diaspore or boehmite when fired in the range 1200° to 1400°C are correlated with the manner in which mullite forms in this temperature range.

Basal spacing data for neutral amine complexes with montmorillonite and vermiculite are explained on the basis of two layers of fully extended amine molecules inclined at about 65° to (001) with the NH2 groups closely associated with pairs of silicate oxygen atoms. The molecular orientation is shown to be favourable for good intermolecular packing and for possible NH..O bonding, but the results do not constitute proof of such bonding. Packing of the molecules on the silicate surfaces and with respect to each other may explain the formation of double layer complexes. The amine data are correlated with corresponding data for the low-temperature (or below melting point) series of alcohol-montmorillonite complexes and it is suggested that the molecular layers may have some solid-like characteristics.