Mixed Bi Research Articles

Barbican-inspired bimetallic core–shell nanoparticles for fabricating natural leather-based radiation protective materials with enhanced X-ray shielding capability

With the wide application of X-rays, the development of flexible and efficient radiation protective materials to reduce the hazards of radiation is in great demand. Inspired by the Barbican defense system, the bimetallic nanocomposites were designed and assembled to trap X-rays photons to experience ordered and cyclic attenuation behavior, where two high-atomic-number elements with different absorption edges, Bismuth (Bi) and Tin (Sn), are assembled into a core–shell nanostructure (Bi@Sn) and were then evenly dispersed into natural leather (NL) to fabricated a high-efficiency wearable radiation protective material (Bi@Sn/NL). Benefiting from the well-defined Barbican-effect mechanism of the core–shell nanostructure, Bi@Sn nanoparticle features more efficient X-ray shielding capability than Bi+Sn nanoparticles mixtures which directly mixed Bi and Sn, and a 2.0 mm-thick Bi2.31@Sn2.43/NL could achieve a comparable attenuation efficiency to a 0.25 mm lead plate and averagely exceeded ∼10.4% than Bi2.31+Sn2.43/NL. Furthermore, Bi2.31@Sn2.43/NL also displays superior physiomechanical properties to the requirements of the Chinese National Standard and features an ultralow density of 1.2876 g cm−3. This work is expected to provide a promising strategy for the design and development of lightweight and high-efficiency wearable radiation protective materials.

Phase and Structural Thermal Evolution of Bi-Si-O Catalysts Obtained via Laser Ablation.

Laser methods are successfully used to prepare complex functional nanomaterials, especially for biomedicine, optoelectronics, and heterogeneous catalysis. In this paper, we present complex oxide and composite nanomaterials based on Bi and Si produced using laser ablation in liquid followed by subsequent powder annealing. Two synthesis approaches were used, with and without laser post-treatment of mixed (in an atomic ratio of 2:1) laser-generated Bi and Si colloids. A range of methods were used to characterize the samples: UV-Vis diffusion reflection, IR and Raman spectroscopy, synchronous thermal analysis, X-ray diffraction, transmission electron microscopy, as well as specific surface-area evaluation. We also followed the dynamics of phase transformations, as well as composition, structure and morphology of annealed powders up to 800 °C. When heated, the non-irradiated series of samples proceeded from metallic bismuth, through β-Bi2O3, and resulted in bismuth silicates of various stoichiometries. At the same time, in their laser-irradiated counterparts, the formation of silicates proceeded immediately from the amorphous Bi2SiO5 phase formed after laser treatment of mixed Bi and Si colloids. Finally, we show their ability to decompose persistent organic molecules of Rhodamine B and phenol under irradiation with a soft UV (375 nm) source.

Effect of single and mixed Bi, Ga doping on the magnetic properties of Y3Fe5O12

The stability, structural, magnetic, and band structure properties of Y3Fe5O12, Y2.75Bi0.25Fe5O12, Y3Fe4GaO12, and Y2.75Bi0.25Fe4GaO12 solid solutions were studied by first-principles calculations. The results demonstrated that the substitution of Bi3+ induces a reduction in the bandgap of Y3Fe5O12. At the same time, Ga3+ was introduced in both the octahedral and tetrahedral sites of Fe3+ and it was found that the bandgap remained almost unchanged. On the other hand, the magnetization was reduced with the incorporation of Bi3+, coinciding with the experimental trend observed in the literature while increasing with Ga3+ incorporation. This behavior is attributed to the disruption of the magnetic sublattices. These results help to understand the ferrimagnetic behavior of YIG and encourage its use as a promising material for optoelectronic and spintronic applications. It is also shown that there is a margin for manipulating the magnetic response through appropriate doping.

The dual role of bismuth in Li2O–Bi2O3–B2O3 glasses along the orthoborate join

AbstractThe structures of glasses in the lithium–bismuth orthoborate composition range deviate significantly from the short‐range order structure of the two crystalline end‐members. Although binary Li3BO3 and BiBO3 are solely of comprised trigonal orthoborate anions, all glasses formed by their combination contain four‐coordinated borate tetrahedra. We analyze the structure of (75−1.5x)Li2O–xBi2O3–(25+0.5x)B2O3 glasses in increments of x = 5, with 11B magic‐angle spinning nuclear magnetic resonance (NMR), infrared (IR), and Raman spectroscopy. For the full series, the oxygen‐to‐boron ratio remains constant at O/B = 3:1. NMR quantifies an increase in the fraction of tetrahedral boron with increasing bismuth oxide content. Evolution of the mid‐IR profile suggests multiple types of tetrahedral boron sites. Raman spectroscopy reveals that Bi2O3 tends to cluster within the lithium borate matrix when initially introduced and that this behavior transforms into a bismuthate network with increasing bismuth oxide content. In all cases, mixed Bi–O–B linkages are observed. The dual role of bismuth as network modifier and network former is likewise observed in the far IR. The glass transition temperature continuously increases with bismuth oxide content; however, the glass stability displays a maximum in the multicomponent glass of x = 40.

Local structure, connectivity and physical properties of glasses in the B2O3-Bi2O3-La2O3-WO3 system

Glasses of (100 - (x + y))·(0.6B2O3·0.4Bi2O3)·xLa2O3·yWO3, x = 0, 10; y = 0 ÷ 40 mol% were prepared by melt quenching. Density measurements, thermal analysis, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and theoretical modeling using Density Functional Theory were employed to identify the effect of WO3 content on the structural and physicochemical properties of these glasses. The glass transition temperature and density increase steadily with increasing WO3 content, most probably because of the formation of mixed Bi–O–W and La–O–W crosslinks. The lower band gap energy values show that the introduction of WO3 or La2O3 to 60B2O3·40Bi2O3 glass increases the number of non-bridging oxygen species in the glass structure. The photoelectron analysis aided by theoretical calculations discover that additionally to the tetrahedrally coordinated W ions, most of the existing WO6 octahedral units in glasses with nominal WO3 content below 20 mol% are distorted, leaving practically the tungsten ions in a quasi-tetrahedral coordination. At higher WO3 content (30–40 mol%) the concentration of octahedrally coordinated tungsten atoms dominate strongly over those of tetra- and quasi-tetra-coordinated W ions. Moreover, the comparison with appropriate crystal standards allows offering a complete description of the existing bridging and non-bridging linkages and their most likely O1s binding energies.

The importance of the active complexes of 6 - mercaptopurine with Bi(III) with regards to kinetics and electrode mechanism changes in the presence of non-ionic surfactants

The presence of mixed adsorption layers affects the mechanism and kinetics of irreversible Bi(III) ions electroreduction process in 2 mol·dm−3 chlorates(VII). Triton X-100 and Tween 80 change the dynamics of the catalytic activity of 6-mercaptopurine (6MP) on Bi(III) ions electroreduction with the tendency of inhibition. Above the critical micelle concentration of Triton X-100 and Tween 80, the irreversibility of Bi(III) ions electroreduction decrease to the size comparable to the irreversible reduction of Bi(III) in 2 mol·dm−3 chlorates(VII) which can be associated with the electrode surface blocking by formed hemispherical surface micelles. It was proved that the unstable complexes of Bi – 6MP or mixed Bi – 6MP – TritonX-100 and Bi – 6MP – Tween 80 intermediating in electrons transfer, play a significant role in the multi-stage mechanism of the electrode process. The hydration shell and composition of active complexes change as well. The obtained regularities indicate that in this case confirmed changes in entropy are a decisive factor.

Small‐Molecule Activation with Molybdenum(0) Complexes Supported by Mixed Imidazol‐2‐Ylidene/Phosphanyl Hybrid Ligands – Electronic and Structural Consequences of Substituting a Phosphane by a Carbene Group

AbstractBy employing a series of mixed bi‐ and tridentate N‐heterocyclic carbene (NHC)/phosphane ligands, the new molybdenum(0) carbonyl complexes [Mo(CO)4(CP)] [1, CP = 3‐(2‐diphenylphosphanylethyl)‐1‐ethylimidazol‐2‐ylidene], fac‐[Mo(CO)3(PCP)] [2, PCP = 1,3‐bis(2‐diphenylphosphanylethyl)imidazol‐2‐ylidene], and fac‐[Mo(CO)3(CPC)] [3, CPC = bis(1‐ethyl‐3‐ethyleneimidazol‐2‐ylidene)phenylphosphane] have been synthesized. The compounds were investigated by X‐ray structure analysis and vibrational and NMR spectroscopy in conjunction with DFT calculations. For comparison, the complexes [Mo(CO)4(CC)] [4, CC = di(1‐ethylimidazol‐2‐ylidene)methane], fac‐[Mo(CO)3(dpepp)] [5, dpepp = bis(2‐diphenylphosphanylethyl)phenylphosphane], and [Mo(CO)4(dppp)] [6, dppp = 1,3‐bis(diphenylphosphanyl)propane] have also been prepared and investigated. In contrast to the phosphane donors, which exhibiting metal–ligand backbonding interactions, the π‐acceptor interactions of the carbene moieties are exactly cancelled by π‐donor interactions. The σ‐donor strengths of phosphane and carbene groups, on the other hand, are found to be comparable. The implications of this result with respect to the activation of small molecules (e.g., N2) are discussed.

The thermal behavior of alumina borate whisker with Bi(OH) 3–Sn(OH) 4 coatings

An alumina borate whisker with Bi(OH) 3–Sn(OH) 4 was prepared using a chemical method. The thermal decomposition of Bi(OH) 3 and the evolution process of Bi 2O 3 (decomposition products of Bi(OH) 3) as well as the thermal stability of the whiskers with coatings were described in detail. It was found that the whiskers are an important factor for accelerating the crystallization and decomposition of Bi(OH) 3. The presence of the whiskers reduced the transition temperature of α- γ Bi 2O 3, but enhanced the transition temperature of γ- δ Bi 2O 3. The reaction between the whiskers and Bi 2O 3 is responsible for the phenomena. In addition, it can be found that the presence of whisker does not change the thermal process of mixed Bi(OH) 3 •Sn(OH) 4.

Primordial non-Gaussianity from a joint analysis of the cosmic microwave background temperature and polarization

We explore a systematic approach to the analysis of primordial non-Gaussianity using fluctuations in the temperature and polarization of the cosmic microwave background (CMB). Following Munshi & Heavens, we define a set of power spectra as compressed forms of the bispectrum and trispectrum derived from CMB temperature and polarization maps; these spectra compress the information content of the corresponding full multispectra and can be useful in constraining early Universe theories. We generalize the standard pseudo-Cl estimators in such a way that they apply to these spectra involving both spin-0 and spin-2 fields, developing explicit expressions, which can be used in the practical implementation of these estimators. While these estimators are suboptimal, they are nevertheless unbiased and robust and hence can provide useful diagnostic tests at a relatively small computational cost. We next consider approximate inverse-covariance weighting of the data and construct a set of near-optimal estimators based on that approach. Instead of combining all available information from the entire set of mixed bi- or tri-spectra, that is, multispectra describing both temperature and polarization information, we provide analytical constructions for individual estimators, associated with particular multispectra. The bias and scatter of these estimators can be computed using Monte Carlo techniques. Finally, we provide estimators, which are completely optimal for arbitrary scan strategies and involve inverse-covariance weighting; we present the results of an error analysis performed using a Fisher-matrix formalism at both the one-point and two-point levels.

The preparation of multimetallic complexes using sterically bulky N-centred tripodal dialkyl phosphino ligands

Sterically bulky monodentate and bidentate phosphines have been widely used as ligands for metal complexation and catalyst formation. Bulky tridentate phosphine ligands are however much rarer and have not been widely investigated even though they may be considered attractive ligands for coordination chemistry studies and catalysis. Here we report the synthesis of two new N-centred tripodal phosphine ligands bearing bulky cyclohexyl and tert-butyl groups. The coordination chemistry of the cyclohexyl triphosphine ligand N(CH 2PCy 2) 3 ( 4) was investigated and found to react with Mo and W hexacarbonyls preferentially forming bidentate metal tetracarbonyl complexes [Mo(CO) 4{N(CH 2PCy 2) 3-κ 2 P}] ( 6) and [W(CO) 4{N(CH 2PCy 2) 3-κ 2 P}] ( 7) over the expected facial capping tridentate complexes. The steric bulk of the cyclohexyl groups on the phosphorus atoms is sufficient to prevent the third arm of the ligand from coordinating and adopting the required geometry for facial coordination. This ‘steric control’ at the metal centre results in the third arm remaining freely available for further metal coordination. The coordination chemistry of this free phosphine arm on complexes 6 and 7 was investigated further and used to prepare a series of gold, platinum and silver multimetallic complexes. The X-ray crystal structures of the resulting mixed bi and trimetallic complexes [W(CO) 4{N(CH 2PCy 2) 3-κ 2 P}AuCl] ( 8), [[Mo(CO) 4{N(CH 2PCy 2) 3-κ 2 P}] 2(μ-PtCl 2)] ( 9) and [[W(CO) 4{N(CH 2PCy 2) 3-κ 2 P}] 2(μ-Ag)]ClO 4 ( 11) are reported.

Effects of Bi 2O 3–WO 3 additives on sintering behaviors and magnetic properties of NiCuZn ferrites

The effects of mixed Bi 2O 3–WO 3 additives on sintering behaviors and magnetic properties of NiCuZn ferrites were investigated. It was confirmed that appropriate additives of mixed Bi 2O 3–WO 3 could enhance densification of specimens, improve initial permeability and Q-factor of NiCuZn ferrites. This was mainly attributed by that appropriate WO 3 additive could improve grain size of the specimen and closed pores are not formed. The maximum initial permeability was achieved with 1.5 wt% Bi 2O 3 and 0.3 wt% WO 3 additives. More WO 3 additive may result in the abnormal grain growth and closed pores inside the grain. The multilayer chip inductor made by composition with 1.5 wt% Bi 2O 3 and 0.3 wt% WO 3 additives exhibited relatively lower dc resistivity, higher inductance and Q-factor than the inductor made by NiCuZn ferrite with only Bi 2O 3 added, this was mainly due to relatively less diffusion of Ag internal electrode and higher initial permeability.

Bi ∼3.785Cd ∼3.575Cu ∼1.5(PO 4) 3.5O 5.5, a new arrangement of double ( [formula omitted]) and triple ( [formula omitted]) [ M4Bi 2n−2O 2n] x+ polycationic ribbons in the bismuth-transition metal oxy-phosphate series

This work is dedicated to investigation of new disordered bismuth-containing oxy-phosphates compounds with an original structure type. As previously observed in this series, they are formed of [M 4Bi 2 n −2O 2 n ] x + polycationic ribbons of width n O(Bi,M) 4 tetrahedra, surrounded by PO 4 groups. In the new crystal structure type, double (= D), triple (= T) and tunnels (= t) alternate along a common axis obeying the TtDtTtDt / TTtTTt sequence in respect to a nomenclature previously described and recalled in this work. The existence this new polymorph has first been detected by electron diffraction in a multi-phased sample. Then, the crystal structure type, i.e., the TtDtTtDt / TTtTTt sequence, has been deduced from HREM images help to a contrast-interpreting code available for these series of polycations-formed compounds. The subsequent compounds formulation leads to a number of new materials that verify the general formula: [Bi 2(Bi, M) 4O 4] 2 [Bi 4(Bi, M) 4O 6] 6 (PO 4) 28 M x , with x ⩽ 12 and M=Cu 2+, Cd 2+ cations. Single crystals of the nominal [O6Bi 4.57Cd 3.43] 4 +8.57 [O 6Bi 4Cd 4] 2 +8 [O 4Bi 2Cd 3.56Cu 0.44] 2 +6 (PO 4) 28 Cu 10.86 have been prepared in a further stage and confirms the predicted crystal structure, Bi ∼3.785Cd ∼3.575Cu ∼1.5(PO 4) 3.5O 5.5, a = 11.506 ( 8 ) Å , b = 5.416 ( 4 ) Å , c = 53.94 (4) Å, β = 90 .10(1)°, R F = 0.0835 , R wF = 0.0993 , SG= A 2 / m , Z=8. As already observed for other elements of this family such as Bi ∼1.2 M ∼1.2O 1.5(PO 4), Bi ∼6.2Cu ∼6.2O 8(PO 4) 5 or Bi ∼3Cd ∼3.72 M ∼1.28O 5(PO 4) 3 ( M=Cu, Co, Zn), this compound shows an additional example of PO 4 disorder due to the presence of mixed Bi 3+/M 2+ sites at the edges of ribbons. The origin and consequence of this so-called disorder mostly occurring on PO 4 configurations is intensively discussed and has been characterized by infrared spectroscopy and by neutron diffraction on similar compounds. It is noticeable that the great number of antagonist PO 4 configurations may order along the b-axis within a large periodicity which involves incommensurate lattice.

Double ( n=2) and triple ( n=3) [ M4Bi 2 n−2 O 2 n] x+ polycationic ribbons in the new Bi ∼3Cd ∼3.72M∼1.28O 5(PO 4) 3 oxyphosphate ( M=Co, Cu, Zn)

The crystal structure of the new Bi ∼3Cd ∼3.72Co ∼1.28O 5(PO 4) 3 has been refined from single crystal XRD data, R 1=5.37%, space group Abmm, a=11.5322(28) Å, b=5.4760(13) Å, c=23.2446(56) Å, Z=4. Compared to Bi ∼1.2 M ∼1.2O 1.5(PO 4) and Bi ∼6.2Cu ∼6.2O 8(PO 4) 5, this compound is an additional example of disordered Bi 3+/ M 2+ oxyphosphate and is well described from the arrangement of double [Bi 4Cd 4O 6] 8+ (= D) and triple [Bi 2Cd 3.44Co 0.56O 4] 6+ (= T) polycationic ribbons formed of edge-sharing O(Bi, M) 4 tetrahedra surrounded by PO 4 groups. According to the nomenclature defined in this work, the sequence is TT/ DtDt, where t stands for the tunnels created by PO 4 between two subsequent double ribbons and occupied by Co 2+. The HREM study allows a clear visualization of the announced sequence by comparison with the refined crystal structure. The Bi 3+/ M 2+ statistic disorder at the edges of T and D entities is responsible for the PO 4 multi-configuration disorder around a central P atom. Infrared spectroscopy and neutron diffraction of similar compounds (without the highly absorbing Cadmium) even suggests the long range ordering loss for phosphates. Therefore, electron diffraction shows the existence of a modulation vector q *=1/2 a *+(1/3+ ε) b * which pictures cationic ordering in the (001) plane, at the crystallite scale. This ordering is largely lost at the single crystal scale. The existence of mixed Bi 3+/ M 2+ positions also enables a partial filling of the tunnels by Co 2+ and yields a composition range checked by solid state reaction. The title compound can be prepared as a single phase and also the M=Zn 2+ term can be obtained in a biphasic mixture. For M=Cu 2+, a monoclinic distortion has been evidenced from XRD and HREM patterns but surprisingly, the orthorhombic ideal form can also be obtained in similar conditions.

Synergy effects between β and γ phases of bismuth molybdates in the selective catalytic oxidation of 1-butene

β+γ mixed Bi–Mo–O phases with a large range of composition were prepared by coprecipitation for investigating the existence of synergetic effects between β and γ phases for the oxidative dehydrogenation of 1-butene. Results from surface characterization show that the surface of the catalysts always has a composition similar to the β phase but the γ phase grows around β phase. Mixed phases present higher activity and less CO 2 selectivity than pure β and γ phases. This result leads to propose that the whole catalyst (bulk and surface) participates in the catalytic process. The synergetic effect between these two phases can be ascribed to the high oxygen mobility in the lattice of the γ phase that allow the migration of oxygen species from the γ to the β phase.

Anisotropic grain growth of Bi 4Ti 3O 12 in molten salt fluxes

Bismuth titanate (Bi 4Ti 3O 12) platelets were obtained by the molten salt synthesis method in NaCl–KCl and Na 2SO 4–K 2SO 4 fluxes, using an amorphous Bi 4Ti 3O 12 precursor and a mechanically mixed Bi 2O 3–TiO 2 mixture as the starting materials. It was found that the synthesizing temperature, salt species and starting materials could significantly affect the crystallization habit and morphology of Bi 4Ti 3O 12 platelets. Under the same processing conditions (i.e. in Na 2SO 4–K 2SO 4 flux at 1000 °C), the Bi 4Ti 3O 12 platelets synthesized from the Bi 2O 3–TiO 2 mixture generally showed a smaller particle size than those synthesized using the amorphous Bi 4Ti 3O 12 precursor. The Bi 4Ti 3O 12 platelets prepared in the chloride flux were faceted along either (0 0 1) or (1 1 2) planes, while those prepared in the sulfate flux were solely (0 0 1) faceted. The former system also had smaller particle size than the latter. Furthermore, the salt content and the addition of plate-like Bi 4Ti 3O 12 seeds in the amorphous Bi 4Ti 3O 12 precursor showed a strong influence on the particle size of the synthesized Bi 4Ti 3O 12 platelets. The particle size of Bi 4Ti 3O 12 platelets prepared in the sulfate flux decreased as the mole ratio of the sulfate salts to Bi 4Ti 3O 12 was increased from 7.9 to 23.7. And the addition of 10 wt.% plate-like Bi 4Ti 3O 12 seeds into the amorphous Bi 4Ti 3O 12 precursor led to a significant increase in the particle size of the resulting Bi 4Ti 3O 12 platelets.

Characterization of the new Bi ∼6.2Cu ∼6.2O 8(PO 4) 5 oxyphosphate; a disordered compound containing 2- and 3-O(Bi, Cu) 4 tetrahedra—wide polycationic ribbons

The present work is dedicated to the XRD, ED and HREM characterization of a new bismuth copper oxyphosphate Bi ∼6.2Cu ∼6.2O 8(PO 4) 5 ( a=11.599(2) Å, b =5.218(1) A ̊ , c=37.541(5) Å, R 1=0.0755, Rw 2=0.174, G.S Pn2 1 a). The relatively long size of its c parameter is due to the arrangement along this direction of two kinds of ribbon-like polycations formed by edge sharing O(Bi, Cu) 4 tetrahedra. The existence of such cations is characterized by the b∼5.2 Å value intrinsic to the ribbons structure and commonly found in bismuth oxyphosphate materials. In the title compound, 2-tetrahedra wide [Bi ∼2.4Cu ∼3.6O 4] 6.4+ and 3-tetrahedra wide [Bi ∼5Cu ∼3O 6] 9+ ribbons are isolated by phosphate groups and alternate along c. The interstitial site created between two different sizes ribbons is occupied by Cu 2+ cations disordered over several close crystallographic sites. The mixed Bi 3+/Cu 2+ nature of certain edge-of-ribbons positions induces a disorder over several configurations of the phosphate groups. The concerned oxygen atoms form the environment of the disordered interstitial Cu 2+ cations which occupy tunnels formed by the phosphate anions. The high-resolution electron microscope study enables a precise correlation between the observed images and the refined crystal structure, evidencing the polycations visualization. Furthermore, this material being the second example of partially disordered compound similar chemical system, some topological rules can be deduced. The b-axis doubling was observed by ED and HREM and is assigned to the ordering of interstitial Cu 2+ within tunnels cations. A partial intra-tunnel ordering was also observed.

New Bismuth(III), Lanthanum(III), Praseodymium (III), and Heterodinuclear Bi–La and Bi–Pr Complexes with Polyaminocarboxylate Ligands

New Bi(III), La(III) and Pr(III) complexes with a variety of high-denticity polyaminocarboxylic acids (H 4edta, H 5dtpa, H 6ttha, H 4Cydta, H 5hpdta, H 4egta) have been synthesized and characterized spectroscopically by FTIR. In the case of the decadentate ttha ligand, homodinuclear M 2(ttha) ( M=Bi, La, Pr) and heterodinuclear MM′(ttha) complexes were isolated. Detailed investigations of their thermal degradation scheme were carried out in relationship with the possible use of these complexes as molecular precursors for the formation of mixed Bi–La and Bi–Pr oxides in which the crystal structure of the fluorite-like δ-Bi 2O 3 phase can be stabilized at room temperature. Decomposition proceeds in three successive stages, consisting of dehydration, ligand pyrolysis leading to monoxo-, dioxo- or simple carbonates, depending on the metal nature, and finally decarbonatation producing the corresponding oxide: α-Bi 2O 3, La 2O 3, Pr 6O 11, BiLaO 3 or BiPrO 3.

The determination of surface polarity of bismuth-molybdenum oxidation catalysts by gas chromatography

The adsorption of aromatic and aliphatic hydrocarbons was investigated using gas chromatography on Bi2O3, MoO3 and mixed Bi−Mo oxidation catalysts. As a measure of polarity of a catalyst, the difference between the chemical potential of aromatic and aliphatic hydrocarbons at the same surface concentration was used. The chemical potentials were estimated from elution chromatographic data. The data for C6−C9 methylbenzenes and C6−C12 n-alkanes were obtained in the temperature range 60–300°C in nitrogen as a carrier gas. Using air as carrier gas, introduction of water pulses on a catalyst does not change the elution characteristics. The elution of alkenes, alkynes, dienes and carbonyl compounds was disturbed by reaction of these compounds on the surface. The polarity of catalysts decreased in the order mixed Bi−Mo catalysts, MoO3, Bi2O3. The polarities observed are compared with polarities of some other solids and liquids and the role of polarity of the surface in catalytic oxidation reactions is briefly discussed.