OH-bending Bands Research Articles

Spray drying of non-chemically prepared nanofibrillated cellulose: Improving water redispersibility of the dried product

Despite increasing interest in using nanofibrillated cellulose (NFC) as food thickener and emulsifier, poor water redispersibility of dried NFC, which is form suitable for practical utilization, significantly limits such applications. Studies are lacking on preparation of dried NFC with superior redispersibility. The present study therefore proposed and examined strategies to improve water redispersibility of spray dried NFC via the use of selected co-carriers, i.e., gum Arabic with/without xanthan gum, carboxymethyl cellulose or pectin. Synergistic interactions between NFC and co-carriers, as confirmed by X-ray diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectra, helped prevent NFC agglomeration during spray drying. All reconstituted spray-dried NFC/co-carriers suspensions exhibited shear-thinning and gel-like behaviors, thus supporting the use of such suspensions as thickener and emulsifier. Spray-dried NFC with 80% gum Arabic and 20% xanthan gum (SD-NFC/GA20XG) resulted in suspension with highest viscosity; the suspension also performed best at recovering viscous characteristics of NFC. Water thickened by SD-NFC/GA20XG had strongest shear-thinning behavior, indicating that SD-NFC/GA20XG suspension resulted in smoothest mouth feel and easiest swallowing. Such observations were supported by XRD patterns of SD-NFC/GA20XG, which suggested that its relative crystallinity was the lowest. Its FTIR spectra also showed the highest intensity of –OH bending and carbonyl bands, which are directly related to water adsorption capability of NFC. Use of reconstituted SD-NFC/GA20XG as emulsifier also resulted in highest stability for oil-in-water (O/W) Pickering emulsion during storage for up to 30 days.

SEM, EDX and vibrational spectroscopic study of the phosphate mineral ushkovite MgFe23+(PO4)2(OH)2·8H2O – Implications of the molecular structure

The mineral ushkovite has been analyzed using a combination of electron microscopy with EDX and vibrational spectroscopy. Chemical analysis shows the mineral contains P, Mg with very minor Fe. Thus, the formula of the studied ushkovite is Mg32+(PO4)2·8H2O. The Raman spectrum shows an intense band at 953cm−1 assigned to the ν1 symmetric stretching mode. In the infrared spectra complexity exists with multiple antisymmetric stretching vibrations observed, due to the reduced tetrahedral symmetry. This loss of degeneracy is also reflected in the bending modes. Strong infrared bands around 827cm−1 are attributed to water librational modes. The Raman spectra of the hydroxyl-stretching region are complex with overlapping broad bands. Hydroxyl stretching vibrations are identified at 2881, 2998, 3107, 3203, 3284 and 3457cm−1. The wavenumber band at 3457cm−1 is attributed to the presence of FeOH groups. This complexity is reflected in the water HOH bending modes where a strong infrared band centered around 1653cm−1 is found. Such a band reflects the strong hydrogen bonding of the water molecules to the phosphate anions in adjacent layers. Spectra show three distinct OH bending bands from strongly hydrogen-bonded, weakly hydrogen bonded water and non-hydrogen bonded water. Vibrational spectroscopy enhances our knowledge of the molecular structure of ushkovite.

Near infrared (NIR) spectroscopy as a tool for monitoring blueberry osmo–air dehydration process

Osmo–air dehydration treatments are widely applied to fruits in order to prolong shelf-life, reduce packaging and logistic costs, and improve both sensory and nutritional quality of the end products. In this work osmo–air dehydration was applied to blueberries (Vaccinium corymbosum), a fruit that is gaining increasing attention due to its high content of dietary antioxidants. In particular, the aim of this study was to investigate the performance of near infrared (NIR) spectroscopy as a tool for monitoring blueberry osmo and air dehydration processes.Blanched blueberries were dipped in sucrose and fructose+glucose osmotic solutions for 24h, and the osmotic exchanges were determined by mass balances (water loss, solid gain, sugar intake, changes in total phenolics and anthocyanins); NIR spectra were collected in order to study modifications due to the osmotic treatments. Untreated and infused berries were subsequently air-dried at 70°C to final moisture content of 10–14%. During drying chemical, nutritional and structural changes were monitored and NIR spectra were acquired on whole berries, using an optic probe working in diffuse reflectance. Spectral data were standardized, transformed into first derivative and processed by Principal Component Analysis. Results show that NIR spectroscopy was able to follow the osmotic and the air-drying processes and to discriminate untreated and osmo-dehydrated berries. Spectral differences reflect the main molecular modifications associated with water absorption bands due to OH stretch+OH bending and sugar absorption bands due to CH stretch+CH bending and OH stretch+OH bending. In order to investigate the variation of main constituents (sugars and water) involved in the osmo-dehydration process, two-dimensional correlation analysis of spectral data was also carried out.

Infrared spectroscopy used to study ice formation: The effect of trehalose, maltose, and glucose on melting

We report the use of infrared (IR) spectroscopy to detect ice crystals in biological solutions. The method is based on the temperature dependence of the OH bending and stretch bands of water. By using mixtures of D 2O and H 2O, water’s absorption bands can be made to be on-scale in transmission mode. Water’s stretch band moves to lower frequency and sharpens with freezing, and the bending band goes to higher frequency and becomes less sharp. The technique is demonstrated for the study of the hysteresis of freezing in the presence of glucosyl sugars, namely glucose, maltose, and trehalose.

Erratum to: Cation mass-valence sum (CM-VS) approach to assigning OH-bending bands in dioctahedral smectites

In the paper ‘Cation mass-valence sum (CM-VS) approach to assigning OH-bending bands in dioctahedral smectites’ from Clays and Clay Minerals, vol. 56, (2008), 10–22, please replace Figure 3b, with this revised version.

Cation mass-valence sum (CM-VS) approach to assigning OH-bending bands in dioctahedral smectites

AbstractThe assignments of OH-bending bands in the infrared (IR) spectra of dioctahedral smectites (montmorillonites, ferruginous smectites, and nontronites) have been revisited using a cation mass-valence sum (CM-VS) approach to quantify octahedral cation occupancy. The CM-VS approach enabled prediction of OH-bending band positions (in wavenumbers) related to OH-sharing octahedral cation pairs that had valence sums of 4 and 5, and cation masses associated with Fe(II) and Mg. Application of rules for the relationship enabled determination of the location of OH-sharing octahedral cation pairs containing Mg and Fe(II) for which previous assignments have been considered controversial, e.g. Fe(III)Mg-OH and MgMg-OH, or for which assignments have been missing due to lack of spectroscopic evidence, e.g. AlFe(II)-OH, Fe(III)Fe(II)-OH, Fe(II)Mg-OH, and Fe(II)Fe(II)-OH. Examples of these bands from several natural ferruginous smectites and nontronites are discussed. Quantification of IR spectra was used to develop a better understanding of the octahedral cation occupancy of this important class of Fe(III)-enriched smectites. While Fe(II) contents may be somewhat overestimated by the IR technique, those for four of the six ferruginous smectites studied here agree well with data from Mössbauer spectroscopy.

Observation of Dynamic Absorption Properties of Wet Gelatin around λ=6.05 µm Using a Mid-Infrared Free Electron Laser

It is essential for soft tissue cutting to precisely predict the effects of laser irradiation before treatment. The purpose of the present study was to investigate the dynamic absorption coefficients of wet gelatin around λ=6.05 µm (tuned to the OH bending and amide-I bands) during laser irradiation. Wet gelatin was irradiated by a tunable mid-infrared free electron laser within the wavelength range of 5.6–6.7 µm. The incident fluence was fixed at 3.6±0.3 J/cm2. Structural changes of the irradiated gelatin were observed with an optical microscope. At λ=6.05 µm, the wet gelatin was efficiently removed due to vaporization of water, and the absorption coefficient during irradiation increased slightly by 30–40% of magnitude from that before irradiation. Thus, we showed the possibility that 6.05-µm-light can predictably remove soft tissue without unexpected effects. A laser system with λ=6.05 µm is expected to be a novel cutaneous laser.

FTIR investigation of the evolution of the octahedral sheet of kaolinite-smectite with progressive kaolinization

AbstractTwenty two samples were studied to investigate the nature and evolution mechanism of mixed-layer kaolinite-smectite (K-S). We examined the <2 µm or <0.2 µm fraction of K-S formed by hydrothermal and hypergenic alteration of volcanic material. The samples are from three localities: 20 specimens from a Tortonian clay deposit in Almería, Spain; one specimen from weathered Eocene volcanic ash from the Yucatan Peninsula, Mexico; and one sample from a weathered Jurassic bentonite from Northamptonshire, England. The samples were studied using chemical analysis, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The XRD patterns of the oriented, glycolated mounts were modeled using NEWMOD and the proportion of smectite and kaolinite layers was determined, ranging between 0 and 80% kaolinite. The analysis of the OH-stretching region of the FTIR spectra at different temperatures (180–550°C) showed the progressive dehydroxylation of kaolinite domains and, perhaps, of smectite domains, but no detailed information could be obtained about the sequential OH loss in different cation environments. The abundance and short-range ordering of the octahedral cations were studied using the OH-bending bands. The chemical and FTIR-estimated octahedral cation abundances were broadly similar. Aluminum showed a tendency to mix with Fe and Mg rather than to form AlAl pairs. Al-for-Mg substitution accompanying kaolinization was evident from the increase in AlAl pairs and decrease in AlMg pairs. Iron is retained in the structure. No other octahedral cation rearrangement was observed. The intensity of the 750 cm−1 band, assigned to translational vibrations of external OH groups in a kaolinitic environment, was quantified and modeled in relation to kaolinite layer proportion. The chemical data show that there are residual interlayer cations in kaolinite domains, which, in accordance with the model mentioned above, disturb external OH-translation vibrations. These results indicate the persistence of certain chemical and structural smectite features in kaolinite domains and thus support a smectite kaolinization process via a solid-state transformation. This confirms previous XRD, thermal, chemical and NMR analyses of the same sample set.

Structural modifications of smectites mechanically deformed under controlled conditions

AbstractSWy-1 and SAz-1 smectites and an Italian bentonite from Sardinia were mechanically deformed via high-energy ball milling for 20 h, in a controlled thermodynamic environment at constant temperature (25°C) under vacuum. The deformed smectites have a lower cation exchange capacity (CEC) and form thicker particles than the original ones, due to agglomeration of smectite crystallites. The 001 diffraction maximum shifted to lower d spacings, the intensity of the 060 reflection decreased and the background at 20-30°2θ increased, suggesting partial amorphization of the smectite. Moreover, the layer charge of the smectites decreased. The intensity of the complex stretching band at 3625 cm-1, and the AlAlOH, and AlFe3+OH bending bands at 916 cm-1 and 886 cm-1, respectively, decreased, while the band at AlMgOH bending at 849 cm-1, disappeared. Deformation mainly disrupted the octahedral sheet and preferentially destroyed those sites occupied by Mg cations, thus explaining the observed decrease in layer charge. Octahedral sites occupied by Fe were least affected. The disruption of the octahedral sheet is substantiated further by the almost total disappearance of the dehydroxylation peak, which is more pronounced in the Mg-rich SAz-1 smectite.

The influence of Zn-dopant on the precipitation of α-FeOOH in highly alkaline media

The influence of Zn-dopant on the precipitation of α-FeOOH in highly alkaline media was monitored by X-ray diffraction (XRD), 57Fe Mössbauer and Fourier transform infrared (FT-IR) spectroscopies and field emission scanning electron microscopy (FE SEM). Acicular and monodisperse α-FeOOH particles were precipitated at a very high pH by adding a tetramethylammonium hydroxide solution to an aqueous solution of FeCl 3. The XRD analysis of the samples precipitated in the presence of Zn 2+ ions showed the formation of solid solutions of α-(Fe, Zn)OOH up to a concentration ratio r = [Zn]/([Zn] + [Fe]) = 0.0909. ZnFe 2O 4 was additionally formed in the precipitate for r = 0.1111, whereas the three phases α-FeOOH, α-Fe 2O 3 and ZnFe 2O 4 were formed for r = 0.1304. In the corresponding FT-IR spectra, the Fe OH and Fe O stretching bands were sensitive to the Zn 2+ substitution, whereas the Fe OH bending bands of α-FeOOH at 892 and 796 cm −1 were almost insensitive. The Mössbauer spectra showed a high sensitivity to the formation of α-(Fe, Zn)OOH solid solutions which were monitored on the basis of a decrease in B hf values in dependence on Zn-doping. A strictly linear decrease in B hf for α-FeOOH doped with Zn 2+ ions was measured up to r = 0.0291, whereas for r = 0.0476 and higher there was a deviation from linearity. The presence of α-(Fe, Zn)OOH, α-Fe 2O 3 and ZnFe 2O 4 phases in the samples was determined quantitatively by Mössbauer spectroscopy. Likewise, Mössbauer spectroscopy did not show any formation of the solid solutions of α-Fe 2O 3 with Zn 2+ ions. FE SEM showed a strong effect of Zn-doping on the elongation of acicular α-FeOOH particles (∼500–700 nm in length) up to r = 0.1111. For r = 0.1304 the sizes of ZnFe 2O 4 particles were around 30–50 nm, and those of α-Fe 2O 3 particles were around 500 nm, whereas a relatively small number of very elongated α-(Fe, Zn)OOH particles was observed. A possible mechanism of the formation of α-(Fe, Zn)OOH, α-Fe 2O 3 and ZnFe 2O 4 particles was suggested.

Raman and infrared spectroscopic study of the vivianite-group phosphates vivianite, baricite and bobierrite

AbstractThe molecular structure of the three vivianite-structure, compositionally related phosphate minerals vivianite, baricite and bobierrite of formula M32+(PO4)2.8H2O where M is Fe or Mg, has been assessed using a combination of Raman and infrared (IR) spectroscopy. The Raman spectra of the hydroxyl-stretching region are complex with overlapping broad bands. Hydroxyl stretching vibrations are identified at 3460, 3281, 3104 and 3012 cm−1 for vivianite. The high wavenumber band is attributed to the presence of FeOH groups. This complexity is reflected in the water HOH-bending modes where a strong IR band centred around 1660 cm−1 is found. Such a band reflects the strong hydrogen bonding of the water molecules to the phosphate anions in adjacent layers. Spectra show three distinct OH-bending bands fromstrongly hydrogen-bonded, weakly hydrogen bonded water and non-hydrogen bonded water. The Raman phosphate PO-stretching region shows strong similarity between the three minerals. In the IR spectra, complexity exists with multiple antisymmetric stretching vibrations observed, due to the reduced tetrahedral symmetry. This loss of degeneracy is also reflected in the bending modes. Strong IR bands around 800 cm−1 are attributed to water librational modes. The spectra of the three minerals display similarities due to their compositions and crystal structures, but sufficient subtle differences exist for the spectra to be useful in distinguishing the species.

Analysis of cation distribution in the octahedral sheet of dioctahedral 2:1 phyllosilicates by using inverse Monte Carlo methods

An inverse Monte Carlo (MC) method was developed to determine the distribution of octahedral cations (Al3+, Fe3+, and Mg2+) in bentonite illite–smectite (I–S) samples (dioctahedral 2:1 phyllosilicates) using FT–IR and 27Al MAS NMR spectroscopies. FT–IR allows determination of the nature and proportion of different cation pairs bound to OH groups measuring the intensities of OH-bending bands. 27Al MAS NMR data provide information about cation configuration because 27Al MAS NMR intensity depends on Fe distribution. MC calculations based on FT–IR data alone show Fe segregation by short-range ordering (Fe clusters within 9 to 15 A from a given Fe atom). Fe segregation increases with illite proportion. MC calculations based on IR and 27Al NMR simultaneously yield similar configurations in which Fe clusters are smaller. The latter calculations fail to build appropriate cation distributions for those samples with higher number of illite layers and significant Fe content, which is indicative of long-range Fe ordering that cannot be detected by FT–IR and 27Al MAS NMR. The proportion of Mg–Mg pairs is negligible in all samples, and calculations, in which the number of Mg atoms, as second neighbours, is minimised, create appropriate configurations.

Infrared Study of Water Sorption on Na-, Li-, Ca-, and Mg-Exchanged (SWy-1 and SAz-1) Montmorillonite

AbstractAn environmental infrared microbalance (EIRM) cell was used to study H2O sorption on two montmorillonite samples as a function of water content and type of exchangeable cation. The vibrational spectra showed that H2O sorbed to the clay at low-water content was strongly influenced by the exchangeable cation and by the close proximity to the clay surface. At water contents <6 H20 molecules per exchangeable cation, the H-O-H bending mode of H2O (v2 mode) shifts to a lower frequency and is characterized by an increase in molar absorptivity. In contrast, the positions of the asymmetric and symmetric OH-stretching modes of sorbed water (v1 and v3 modes) shift to higher energies. These observations indicate that H2O molecules sorbed to the clay surface at low-water content are less hydrogen bonded than in bulk H2O. In addition, the vibrational-stretching and bending bands of the structural OH groups of the 2:1 layer are also strongly influenced by H2O content and type of exchangeable cation. By using the EIRM cell, the molar absorptivities of the structural OH-bending vibrations were measured as a function of H2O content. The position and molar absorptivity of the structural OH-bending bands at 920, 883, and 840 cm-1 are strongly influenced by H2O content and type of exchangeable cation. The molar absorptivity of the 920-cm-1 band, which is assigned to the AlAlOH group, decreased strongly at low-H2O content. This reduction in intensity is assigned to a dehydration-induced change in orientation of the structural OH groups resulting from the penetration of H2O molecules into siloxane ditrigonal cavities that are not associated with a net negative charge from isomorphous substitutions.

Analysis of Fe segregation in the octahedral sheet of bentonitic illite-smectite by means of FTIR, 27 Al MAS NMR and reverse Monte Carlo simulations

A series of bentonite illite/smectite with a range of Fe content (0.08-0.95 atoms per half formula unit) and illite composition (3-97 percent illite) has been analyzed by means of FTIR, ^27^ Al MAS NMR, and theoretical calculations by reverse Monte Carlo simulations to study cation distribution in the octahedral sheet. FTIR was used to determine the proportion of different cation pairs bound to OH groups utilizing the OH bending bands. The proportions of cation pairs were used to generate Monte Carlo distributions of the octahedral cations in the layers. The calculated distributions were then analyzed in comparison with the experimental ^27^ Al NMR results. All samples have shown a high dispersion of the Mg cations and a tendency for Fe segregation which increased with progressing illitization. The illite-rich samples showed medium- or long-range ordering of the octahedral cations. The minimum radius for the wipeout sphere of the ^27^ Al NMR signal around Fe atoms is 7.5 Aa, for our working conditions of 11.7 T.

Preparation and infrared spectroscopic characterization of reduced-charge montmorillonite with various Li contents

AbstractA series of reduced-charge montmorillonites (RCMs) was prepared from Li-montmorillonite from Jelšový Potok (Slovakia) by heating at various temperatures (105–210°C for 24 h. The amount of fixed Li, 0.09–0.67 per O20(OH)4, increased with increasing temperature, confirming preparation of a set of samples of variable layer charge from the same parent Li-montmorillonite by varying only the preparation temperature. Infrared spectroscopy revealed that Li was trapped in the hexagonal cavities of the tetrahedral sheet at all temperatures. Partial deprotonation of the samples, reflected in the decrease of the intensities of the OH-bending bands, was observed after treatments above 120°C. Analysis of the OH-stretching region showed Li in the previously vacant octahedra in the samples heated above 150°C. Weak inflections near 660 and 720 cm−1 confirmed development of local trioctahedral character of octahedral cations coordinated with OH groups in the sample heated at 210°C. Gradual decrease of the layer charge due to Li fixation led to a shift of the Si-O stretching band to higher frequencies and to the appearance of new, pyrophyllite-like bands at 1120 and 419 cm−1.

Fourier-transform infrared spectroscopy, torsion-vibration coupling, and new far-infrared laser assignments for ^13CD_3OH methanol

High-resolution Fourier-transform spectra of the lower vibrational fundamentals of the 13CD3OH isotopomer of methanol are under investigation in the 800–1350-cm−1 region, including the ν8 in-plane CD3-rocking (A′), ν7 CO-stretching (A′), ν5 CD3-deformation (A′), and ν4 OH-bending (A′) bands. The torsion–vibration–rotation energy-level manifold for these lower modes displays numerous perturbations that are due to torsion–vibration interactions and contains a variety of features of interest in the excited-state energy-level patterns. Analyses of the bands show that there are major problems in formulating effective Hamiltonians and in determining reliable molecular constants for the excited states because of strong torsion–vibration coupling. Assignments for five far-infrared laser transition systems have been deduced; these involve the CD3-rocking, CO-stretching, and CD3-deformation states.

The influence of aluminium on iron oxides: XIII. Properties of goethites synthesised in 0·3 M KOH at 25°C

AbstractAluminium-substituted goethites were synthesised in 0·3 M KOH at either 25° or 70°C. The 25°C goethites had unit-cell a and c dimensions about 0·1–0·2% larger than the 70°C goethites of comparable Al substitution. Unit-cell b dimensions were similar regardless of synthesis temperature. The 25°C goethites contained larger amounts of Al in their structures than the 70°C goethites synthesised at the same initial Al/(Al + Fe) mole ratio in solution. The 25°C goethites had lower dehydroxylation temperatures and smaller differences between the two OH-bending bands than comparable 70°C goethites. These differences between the two sets of goethites are believed to be caused by the presence of more structural defects in the 25°C goethites than in the 70°C goethites. Goethites with the lowest Al substitutions consisted of crystals with several coherently diffracting domains, while at high Al substitutions the crystals were mainly monodomainic. Surface areas of the 25°C goethites varied in a complex manner as a function of thickness along [100], character of the domains, and physical size.

Incorporation of chlorine into hydroxy-apatite

Ca 5OH(PO 4) 3 and Ca 5Cl(PO 4) 3 readily form solid solutions Ca 5(OH 1− x Cl x )(PO 4) 3, if synthesized at 1000°C under p H 2O = 4 Torr from CaHPO 4, Ca(CH 3COOH) 2 and CaCl 2. The crystallographic a-axis expands from 9.418 to 9.634 Å, the c- axis contracts from 6.884 to 6.778 Å with increasing Cl content. A new OH stretching band appears in the IR spectrum at 3496 cm −1 for x < 0.5. Two new OH bending bands appear at 755 and 795 cm −1 for x > 0.5. By comparison with the corresponding IR bands in the hydroxy-fluoroapatite solid solution it is to be concluded that the OH…Cl hydrogen bond is stronger than the OH…F bond. This anomalous behavior reflects the difficulty encountered when Cl − substitutes for OH − in the (OH, Cl)-apatite. The large Cl − prefers the halfway position between the Ca-triangles (as in pure Cl-apatite) whereas the OH − sits slightly above or below the plane of the three Ca 2+ (as in pure OH-apatite). Geometrically this is unfavorable leading to the a-axis contraction and to the OH…Cl compression. The seemingly strong hydrogen bond found in (OH, Cl)-apatite solid solutions destabilizes the structure and explains why, under biological conditions, the OH-apatite discriminates against Cl −.

Reactivity of a long-spacing ammonium-propionate-kaolinite intercalate toward diol, diamines and quaternary ammonium salts

AbstractThis paper describes reactions occurring between the 25.5 Å ammonium propionate (AP) intercalate of a well-crystallized Georgia kaolinite with ethylene glycol, 1-6-diaminohexane and a quaternary amine (QA), namelyAn ethylene glycol kaolinite complex is obtained with a strong d001 reflection at 10.9 Å. Seven 00l orders are observed easily. The IR spectrum shows bands at 3697, 3654 (weak shoulder) 3644 and 3622 cm−1, assigned to OH stretching of kaolinite and a strong OH band of E.G. at 3300 cm−1. No absorption band of AP is observed.The 1.6-diaminohexane product is characterized by two broad reflections at 16.6 and 7.4 Å. Distinct Amide I and Amide II IR bands imply that the carboxyl group of the propionic acid has reacted with the amino group. By treating the AP complex with QA a very stable kaolinite-QA complex suspension in benzene was obtained. On drying an X-ray amorphous solid with no reflection at spacing &amp; 20 Å was obtained. The hydroxyl stretching bands of the original kaolinite are drastically modified, a very strong band at 3560 cm−1, a strong doublet at 3620 and 3605 cm−1 were observed. A weak singlet is obtained at 3695 cm−1. The two OH bending bands are replaced by a single band at 912 cm−1. A complicated set of interactions results in the loss of stacking order about the C-axis, accompanied by some curling of layer packets. A prolonged treatment with water restores the X-ray and IR spectra of the original kaolinite.

Nature of water at the rutile/organic liquid interface

AbstractThe nature of trace water on rutile surface has been investigated by means of adsorption, electrophoresis and infrared analysis as a prelude to the study of the affects of trace water on dispersibility. The isosteric heats of adsorption of water on rutile revealed the presence of two types of water on the rutile surface. The isosteric heat was found to increase from 11 to 27 kcal/mole at a fractional water coverage of 0.1. Further‐more, this increase was observed only at temperatures above 120°C. Further support for this theory was evidenced by the electrophoretic mobility of rutile in heptanol which first increased and then decreased with increasing water coverage.Infrared analysis of water adsorbed on rutile revealed the presence of isolated OH groups on the surface. Based on the relative intensities of the infrared CH2 and OH bending bands, the adsorption of heptanol, n‐hexylamine and n‐heptanoic acid was at a maximum at a water coverage of 0.08.Average aggregate size produced by ultrasonic dispersion in a closed system as revealed by ultramicroscope examination, was also at a minimum at a coverage of 0.08. An important factor affecting dispersibility was concluded to be the Rehbinder effect as well as the double layer repulsion.