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A manganese–cobalt (Mn1.5Co1.5O4) spinel compound was synthesized by means of gel processing with EDTA (ethylenediaminetetraacetic acid) as a chelating agent binding Mn and Co in aqueous solutions. The phases obtained in the process were stable and formed an amorphous gel, which was then annealed in air at temperatures of up to 1153 K. Structural and thermal evolution of the product formed after the decomposition of the gel precursor at different temperatures was traced using XRD and FTIR studies as well as DSC/TG methods, respectively. The obtained results indicated that the gel precursor decomposed entirely at temperatures higher than 993 K, while the crystallization of the Mn1.5Co1.5O4 spinel with an intermediate tetragonal/cubic structure began at a temperature as low as 553 K. Both XRD and FTIR studies revealed an increasing fraction of the tetragonal phase up to 853 K and no further change at higher temperatures. Moreover, at 1033 and 1153 K FTIR studies of the material revealed partial inversion of the spinel. [ABSTRACT FROM AUTHOR]

Multicomponent cobalt phosphate–silicate glasses from P2O5–SiO2–K2O–MgO–CaO–Co2O3 system in which molar ratio of P2O5 to SiO2 is 41:6 and cobalt ions are gradually incorporated at the expense of magnesium and calcium ions were prepared via melt-quenched technique. The obtained amorphous solids were subjected to the thermal and spectroscopic studies and density measurements in order to gain information about the structure and physical properties. As DSC, XRD, FTIR and pycnometry techniques were applied, the glass transition temperature, specific heat change, crystallization temperature, density, molar volume, oxygen packing density and associated infrared spectra were collected for each glass. Then, the process of induced crystallization was performed on the selected glass samples. The related glass-crystalline materials were evaluated via XRD method. As a result, crystalline phases associated with crystallization temperature were identified. The alterations in determined parameters, stoichiometry of connected crystalline phases and features of infrared spectra allow to conclude the impact of cobalt ions on structure of analyzed glasses due to the direct dependence of structure, physical and thermal properties. The conducted research constitutes a basis for further analysis of cobalt phosphate–silicate glasses and makes a contribution to the knowledge concerning the phosphate glasses family. [ABSTRACT FROM AUTHOR]

Frying is one of the most common methods used in food preparations, as it improves sensory properties, making it more attractive to the consumer. Palm oil is one of the most used oils in frying; however, its high amount of saturated fatty acids makes it harmful to cardiovascular health when frequently ingested. In the present study, aiming to improve the nutritional properties of palm oil (PO) and the thermal and oxidative stability of soybean (SO) and sunflower (SFO) oils, nine blends were prepared with different ratios of PO, SO, and SFO. The study also compared the effect of commercial antioxidants on the oxidative stability of SO and SFO. According to the obtained results, the nine blends presented a better saturated/unsaturated ratio compared to PO, and their periods of oxidative induction increased when compared to pure SO and SFO oils. According to the expression of the characteristic absorption band of trans double bonds, the proportion of the palm oil used in the blends did not influence the formation of trans fatty acids. The combinations with lower PO content and higher SO and SFO oils ratios resulted in a healthy fatty acid profile, leading to the best choice for consumers. [ABSTRACT FROM AUTHOR]

Iron phosphate-silicate glasses from P2O5–SiO2–K2O–MgO–CaO–Fe2O3 system were subjected to the thermal and spectroscopic studies in order to gain information about their structure and thermal behavior in the range of glass transition effect. Research includes results obtained via DSC, MIR and DRIFT spectroscopy. Designated values of glass transition temperature and specific heat change slightly increases with Fe2O3 incorporation. Spectra collected during thermal treatment of glasses containing 2 and 30 mol% Fe2O3 exhibited various changes. Fe2O3 addition affected the glass structure by its reinforcement and led to its preservation during thermal treatment. The connection between density, molar volume, oxygen packing density and the chemical composition's alteration were also established because of the direct dependence of physical properties and the structure. Obtained results supported thermal and spectroscopic studies. Conducted research is considered as a contribution to the knowledge about the family of iron phosphate glasses, which are known from their interesting properties and widely used applications. [ABSTRACT FROM AUTHOR]

A systematic thermodynamic study has been performed for a series of nitrates having cations derived from the α-amino acids glycine (Gly), l-proline (Pro) and l-glutamine (Gln). Combustion and formation enthalpies were for the first time obtained for these amino acid nitrates (AANO3) by using combustion calorimetry. The thermal behavior in the dynamic regime was investigated by DSC measurements. The values of the formation enthalpies for nitrates were compared with those of the corresponding amino acids and discussed in correlation with structural information obtained from spectral data. FTIR and Raman techniques were used to identify functional groups and hydrogen bonds. Large transmittance in the visible region and the band gap energy value obtained from UV–Vis spectra suggest that these materials are suitable for optoelectronic applications. The band gap values are increasing in the order GlyNO3 < ProNO3 < GlnNO3. Additional polarimetric measurements confirmed the chiral nature of ProNO3 and GlnNO3. [ABSTRACT FROM AUTHOR]

The cleavage behavior of covalent bonds in Xilinguole (XLGL) lignite and changes in chemical structure of lignite and its chars during low-temperature pyrolysis were investigated by thermogravimetric (TG) analysis and Fourier-transform infrared (FTIR) spectroscopy. Based on the TG and differential thermogravimetric (DTG) analysis results, the cleavage of different types of chemical bonds in lignite occurred mainly at four certain temperatures, 170 °C, 376 °C, 432 °C, and 521 °C. The latter three were selected as the final pyrolysis temperatures of chars evaluated in this study. The FTIR analysis results indicate that thermal treatment increased the relative content of two and three adjacent H deformation structures but decreased that of four adjacent H deformation structure. This was caused by the cleavage of Cal–Cal and Car–Cal bonds. The oxygen-containing functional groups in lignite are dominated by C–O and C–OH groups with a lower chemical reactivity than C=O–C and conjugated C=O groups. Moreover, XLGL lignite has the highest ratio of CH2/CH3 which declines with increasing temperature, indicating the decrease in the length of aliphatic chains and increase in the degree of branching of aliphatic side chains. This change mainly resulted from the cleavage of Cal–O, Cal–Cal, and Car–Cal bonds. Furthermore, XLGL lignite and its chars contain five specific hydrogen bonds: OH–N, cyclic OH, OH–ether O, OH–OH, and OH–π hydrogen bonds. The relative content of OH–OH hydrogen bond was the highest, indicating that OH–OH hydrogen bond has the highest thermal stability. [ABSTRACT FROM AUTHOR]

In the present paper, we reported the accurately measured densities (ρ), speed of sound (u) and refractive index (nD) for the binary mixture of 1-butyl-3-methylimidazolium hexafluorophosphate [Bmim] [PF6] with N-vinyl-2-pyrrolidinone (NVP) as a function of concentration at six temperatures from 298.15 to 323.15 K at atmospheric pressure. From the measured density, speed of sound and refractive index, the excess molar volumes, VmE, excess isentropic compressibilities, κsE, excess speeds of sound, uE, excess molar isentropic compressibility, Ks,mE, deviation in refractive index, ΔϕnD and deviation in molar refraction, ΔRM have been calculated and satisfactorily fitted using the Redlich-Kister polynomial equation. Partial molar volumes and molar isentropic compressibilities were calculated. Infinite dilution values of these derived thermodynamic properties have also been calculated. Evaluation of refractive index has been carried out by nine mixing rules, to investigate their validity for these mixtures over the entire mole fraction of [Bmim][PF6] at all investigated temperatures. Comparison of these approaches has been presented in terms of APD. Furthermore, the FTIR measurements of these mixtures are carried out at 298.15 K to study the complex formation between [Bmim][PF6] and NVP. Changes in the measured and calculated values of the physicochemical parameters as a function of temperature and composition of the mixture were analysed in terms of interactions. The results were used to quantitatively analyse the effects of organic solvent NVP with [Bmim] [PF6] and compared with other anions of [Bmim]. [ABSTRACT FROM AUTHOR]

Adamantan-2-one is an adamantane derivative used as a precursor in the synthesis of different pharmacologically active substances, i.e., memantine hydrochloride which was investigated in one of our previous published papers, both as pure compound and in binary mixtures. The aim of our study is to determine the influence of the oxo group regarding the thermal stability of the hydrocarbon structure and also to evaluate possible interactions of the functional groups with various compounds used as excipients. For this purpose, we evaluated the thermal behavior of adamantan-2-one and its compatibility with some excipients used in drug formulations. The pure compounds and the binary mixtures of adamantan-2-one with different excipients were investigated by TG/DTG/HF thermal methods in dynamic air flow, at a heating rate of 10 °C min until 550 °C and by FTIR spectroscopy. [ABSTRACT FROM AUTHOR]

Magnetic iron oxides were prepared by precipitation of Fe(II) hydroxide using different precipitation agents: ammonia, benzylamine and sodium hydroxide, followed by oxidation with the oxygen dissolved in water. Thermal analysis, coupled with FTIR spectroscopy, has evidenced the formation of a mixture of magnetite and maghemite, with a higher content of magnetite in case of the powder synthesized with benzylamine. The stability of magnetite at oxidation by air during storage at room temperature and 60 °C was investigated by means of TG/DSC simultaneous thermal analysis, FTIR spectroscopy and X-ray diffractometry. Thermal analysis evidenced an exothermic process with mass gain in temperature range 100-190 °C, corresponding to magnetite oxidation process, but due to the superposition of other processes it could not offer quantitative information. FTIR spectroscopy has provided, especially through the first and second derivatives of FTIR spectra, the most valuable information regarding the evolution of magnetite to maghemite, due to their different characteristic bands. XRD technique has evidenced a slight shift of the main diffraction peaks at higher 2-theta values during the evolution of magnetite to maghemite. According to thermal analysis data, the powder synthesized with ammonia was completely oxidized after 15 days, while the other two powders, synthesized with benzylamine and sodium hydroxide, were completely oxidized after 110 days of keeping in air at room temperature. For a temperature of 60 °C, the oxidation was much faster; the oxidation process of the powder synthesized with benzylamine disappeared from TG/DSC curves after 1 day. All final powders were formed from nanoparticles with diameters up to 25 nm, with magnetic properties characteristic to nanometric maghemite. [ABSTRACT FROM AUTHOR]

This study presents the synthesis of polyesters obtained from phthalic anhydride as acidic components and one mixture of monoethylene glycol and monohydric alcohol (in ratio 1.1:0.15). Molar ratio of the acid component and alcohol component was 1:1.25. n-Propanol, n-butanol, n-octanol and isoamyl alcohol were used as monohydric alcohol. Physicochemical characterization was performed by elemental analysis, FTIR/UATR spectroscopy of polyesters and char, EGA (evolved gas analysis), thermal analysis in synthetic air and in nitrogen atmosphere. [ABSTRACT FROM AUTHOR]

A novel semiorganic optical material (Bis) isonicotinamide perchlorate monohydrate (BINPM) has been synthesized, and crystals were grown by the slow evaporation solution growth technique. The crystal structure of BINPM was elucidated by single crystal X-ray diffraction technique. It revealed that the grown crystal belongs to monoclinic system with a space group P2/c and that the unit cell parameters are a = 7.6480(5) Å, b = 23.4754(16) Å, c = 9.0915(6) Å, α = γ = 90° and β = 106.548(2)°. UV-Vis-NIR spectral study revealed that the BINPM crystal has a wide transmission window in the entire visible region with a lower cut-off wavelength 311 nm. The molecular structure of the title compound was confirmed by FTIR and FTNMR spectral studies. Thermogravimetric and differential thermal analyses revealed the thermal stability of BINPM compound. The luminescence study showed a violet emission of BINPM compound. Microhardness and etching studies were also carried out on the samples, respectively. The dielectric constant and dielectric loss of the crystal were measured as a function of frequency and temperature, and the results are discussed. [ABSTRACT FROM AUTHOR]

Nowadays, there is the widespread use of clay minerals as fillers in polymeric materials. One of the most widely used mineral is montmorillonite belonging to the smectite. We have prepared organically modified clays using two different types of accelerators TP and ZDT for sulfur vulcanization. Intercalation of these accelerators into the interlayer of clays was performed using a gas reaction at room temperature. They were examined (characterized) by thermal analysis (DTA, TG), X-ray analysis, and infrared spectroscopy (FTIR). [ABSTRACT FROM AUTHOR]

Single crystals of di-μ-thioureabis(thiocyanato)cobalt(II), Co(NCS)(tu) (tu-thiourea) are grown by slow evaporation of a mixed solvent system water-methanol (1:1, v/v) containing thiourea, potassium thiocyanate, and cobalt chloride (1:1:0.5) at room temperature. The dark brown plate-like crystals belong to triclinic system with space group $$P\overline{1}, $$ and the cell parameters are a = 3.8469(7) Å, b = 7.5749(13) Å, c = 10.1184(17) Å, α = 92.599(8)°, β = 98.036(8)°, γ = 104.132(7)°, V = 282.15(9) Å, and Z = 1. The cobalt atom lies at the center of symmetry with four bridging thiourea molecules. The powder X-ray diffraction study reveals the crystallinity of the material. The complex formation is evidenced by the vibrational patterns in Fourier transform infrared spectrum. The scanning electron microscopy study reveals the surface morphology of the metal-thiourea complex. Thermogravimetric and differential thermal analysis shows that the complex is stable up to the melting point. The crystal is further characterized by UV-Vis and mechanical studies. [ABSTRACT FROM AUTHOR]

Thermal decomposition of HAuCl·3HO and AgNO, as precursors for Au and Ag nanoparticles, respectively, was monitored by coupled TG-DTA with TG/EGA-FTIR and EGA-MS techniques in a flowing 80 %Ar + 20 %O and Ar atmospheres in the temperature range of 30-600 °C. The intermediate and final products of thermal decomposition were analysed by ex situ XRD and FTIR techniques. The thermal degradation of HAuCl·3HO starts immediately after melting at 75 °C and takes place in three steps in the temperature range of 75-320 °C with total mass loss of 49.4 and 49.7 % in artificial air and Ar atmospheres, respectively. EGA by MS and FTIR revealed a simultaneous release of HO and HCl in the temperature range of 75-235 °C. EGA by MS revealed a release of Cl at around 225 °C and in the interval of 250-320 °C. According to the XRD analysis, the main solid product in the end of the first decomposition step at 190 °C is AuCl; in the end of the second decomposition step at 240 °C is AuCl and the final product at 320 °C is Au. The thermal decomposition of AgNO takes place in a single step in the temperature range of 360-515 °C with a total mass loss of 39.0 and 37.8 % in flowing artificial air and Ar atmospheres, respectively. According to EGA-MS and EGA-FTIR the main evolved gases are NO, NO and O. The final product of the thermal decomposition at 600 °C is Ag irrespective of the atmosphere. [ABSTRACT FROM AUTHOR]

The polyaniline dispersions stabilized with poly( N-vinylpyrrolidone) (PANI/PVP) were synthesized by oxidative polymerization with different mass ratios of PANI and PVP and different molar concentrations of the components in the polymerization mixture. The composite powders prepared from colloidal PANI/PVP dispersions were characterized by thermogravimetry and differential thermal analysis. The change in the ratio of PANI and PVP as well as the starting molar concentrations of aniline hydrochloride and oxidant has influence on the resulting properties of the dispersions. Concerning the doping, the results show that PANI/PVP powders are stable up to approximately 160 °C. Degradation of polymer chains starts at temperatures above 250 °C. The PANI/PVP composite powders with lower content of PANI exhibit slightly higher thermal stability. Further, colloidal PANI/PVP dispersions were screen-printed on aluminum foil for infrared spectroscopic characterization and on poly(ethylene terephthalate) foil for electrical measurements. The sheet resistance of printed layers measured by two-point probe was of the order of tens to thousands of kΩ sq. The influence of both the change in the composition and the drying temperature is discussed. [ABSTRACT FROM AUTHOR]

Two different compounds have formed from liquid enantiomeric ( R-) and racemic α-methylbenzylamine (α-MBA, named also as 1-phenylethylamine, 1-FEA) with supercritical fluid CO. The crystalline solids have been characterized by elemental CHN analysis, X-ray diffraction (XRD), FTIR, H, and C NMR spectroscopy, and found to be α-methylbenzylammonium α-methylbenzylcarbamate self-derivative ionic salts 1 ( R/ R) and 2 ( rac RS), respectively, of the corresponding amines. Compound 2 ( rac RS) has shown different XRD pattern from that of enantiomerically pure 1 ( R/ R), indicating a preferential formation of a 1:1 mixture of ( R/ S-) and ( S/ R-) or rather a racemate compound of ( RS/ SR-) ammonium carbamate salt ( 2 ( rac RS)) from racemate. For thermal stability, the compounds have been checked by differential scanning calorimetry (DSC), simultaneous thermogravimetry and differential thermal analysis (TG/DTA), and in situ coupled evolved gas analysis by mass spectroscopy (TG/DTA−EGA−MS) and FTIR-gas cell (TG−FTIR). No melting point is observed because of the low thermal stability of the compounds. Decomposition stages are tried to be separated with using semi-closed (sealed with a pinhole on the top) crucibles, thus different evolution courses of CO and organic vapors could be followed by MS and FTIR spectroscopy. The α-MBA vapors themselves, evolved from open crucibles could be identified by FTIR-gas cell, while vapors up to m/ z = 164 have been detected by MS from semi-closed Al crucible. [ABSTRACT FROM AUTHOR]

The indium complex, mer-trichlorotris(thiourea)-indium(III) (In(tu)Cl, 1), crystallized from aqueous solution of InCl and SC(NH) (tu) with molar ratio of 1:3, is a single-source precursor for InS films by chemical spray pyrolysis. The structural model of the triclinic crystal 1 (space group P-1 with a = 8.4842(2) Å, b = 10.5174(2) Å, c = 13.1767(2) Å, α = 111.1870(10)°, β = 98.0870(10)°, γ = 97.889(2)°) has been improved by single crystal X-ray diffraction analysis through successful separation of the disordered positions of the asymmetric complex molecule situated on the inversion centre into two spatial arrangements. Thermal decomposition of 1 occurs with very similar mass loss courses till 400 °C in both nitrogen and air, anyhow the DTA curve indicates a gas-phase oxidation with an additional exothermic heat effect at 255 °C in air. Partial or more advanced oxidation of the initially evolved CS has taken place in both atmospheres, as its oxidation products, SO, COS, CO are accompanied by the release of NH, HCl in temperature range of 205-275 °C, while HNCN and HCN evolve in air. In the third mass loss step, in the temperature interval of 405-750 °C in nitrogen and 405-700 °C in air, two processes, evaporation and oxidation of the solid residues are competing with each other, resulting in final decomposition product of 1 in air InO, while also some InO in inert atmosphere beyond the main phase of InS where, in addition considerable extent of loss of indium occurs, probably through volatile dimeric indium chloride species, which could not be detected either by EGA-MS or EGA-FTIR systems of ours. Nevertheless, evolution of HNCS is confirmed by EGA-FTIR, and release of CO, HNCN, SO, and a little HCl is detected at temperatures above 450 °C in both atmospheres. [ABSTRACT FROM AUTHOR]

This paper is devoted to the investigation of the properties of the natural rubber composites prepared using the cation exchanged-montmorillonite fillers. The characteristics of the montmorillonite fillers were studied by Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG). These characterized fillers were used to preparation of the natural rubber composites, which were submitted to measurements of dynamic-mechanical thermal analysis (DMTA) and vulcanizing characteristics ( M, M, t, t, R) as well as physico-mechanical properties (tensile strength, modulus at 300 elongation- M, tensibility). [ABSTRACT FROM AUTHOR]

A new co-crystal of theophylline and phthalic acid with 1:1 molar ratio has been prepared. It crystallises in the monoclinic crystal system, space group P21/ c, a=11.5258(9), b=10.1405(6), c=13.9066(12) Å, β=106.827(4)°. The structure of the co-crystal has been revealed by single crystal X-ray diffraction. An infinite helical polymeric chain is formed by intermolecular hydrogen bonds of the two neutral constituents. The hydroxyl group and carbonyl oxygen atom in one of the carboxyl groups of phthalic acid form hydrogen bonds to O6 and to N(7)H atoms of theophylline, respectively, while the other carboxyl OH group of phthalic acid is in hydrogen bond to N9 atom of theophylline by very strong intermolecular interactions proven by 1883 cm−1 centred peak in FTIR spectrum. Thermal degradation of this new supramolecular compound is a two-step process in air. At first phthalic acid (47.4%) released up to 230°C, meanwhile it loses water and transforms into phthalic anhydride. In EGA-MS spectra, the characteristic fragments of water ( m/ z=17, 18) appear from about 180°C, while absorption bands of phthalic anhydride are shown in EGA-FTIR spectrum at about 210°C. In the second step theophylline begins to sublime, melts at 276°C, and then evaporates up to 315°C with minute residues. [ABSTRACT FROM AUTHOR]

Thermal decomposition of ammonium paratungstate tetrahydrate, (NH4)10[H2W12O42]·4H2O has been followed by simultaneous TG/DTA and online evolved gas analysis (TG/DTA-MS) in flowing 10% H2/Ar directly up to 900°C. Solid intermediate products have been structurally evaluated by FTIR spectroscopy and powder X-ray diffraction (XRD). A previously unexplained exothermic heat effect has been detected at 700–750°C. On the basis of TG/DTA as well as H2O and NH3 evolution curves and XRD patterns, it has been assigned to the formation and crystallization heat of γ-tungsten-oxide (WO2.72/W18O49) from β-tungsten-oxide (WO2.9/W20O58) and residual ammonium tungsten bronze. [ABSTRACT FROM AUTHOR]

Several calcium silicate hydrate (C–S–H)-polymer nanocomposite (C–S–HPN) materials have been prepared by incorporating poly(acrylic acid) (PAA) into the inorganic layers of C–S–H during precipitation of quasicrystalline C-S-H from aqueous solution. The synthetic C–S–HPN materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS), thermogravimetry (TG), differential thermogravimetry (DTG) and differential scanning calorimetry (DSC). The XRD peaks of C–S–HPN materials suggest the intermediate organizations presenting both intercalation of PAA and exfoliation of C–S–H. The SEM images of C–S–H and C–S–HPN materials with different PAA contents exhibit the significant differences in their morphologies. Effects of the material compositions on the thermal stability of series of C–S–HPN materials along with PAA and C–S–H has been studied by TG, DTG and DSC. Three significant decomposition temperature ranges were observed on the TG curves of all C–S–HPN materials. [ABSTRACT FROM AUTHOR]

A series of calcium silicate hydrate (C–S–H)-polymer nanocomposite (C–S–HPN) materials were prepared by incorporating poly(acrylic acid) (PAA) into the inorganic layers of C–S–H during precipitation of quasicrystalline C–S–H from aqueous solution. The as-synthesized C–S–HPN materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The XRD analysis of C–S–HPN materials suggest the intermediate organizations presenting intercalation of PAA within C–S–H and exfoliation of C–S–H. The SEM micrographs of C–S–H, PAA and C–S–HPN materials with different PAA contents exhibit the significant differences in their morphologies. The effect of the material’s composition on the thermal stability of a series of C–S–HPN materials along with PAA and C–S–H were studied by TG, DTA and DSC. Three significant decomposition temperature ranges were observed on the TG curves of all C–S–HPN materials. [ABSTRACT FROM AUTHOR]

Inclusion complexation between dimethyl-β-cyclodextrin and a very poorly water-soluble serum lipid-regulating agent, gemfibrozil, was studied. Products were prepared by several methods (physical mixing, kneading, spray-drying and ultrasonic treatment) in four different molecular ratios (2:1, 1:1, 1:2 and 1:3). The possibility of complex formation between the drug and the host molecule was studied by thermal analysis. Supplementary techniques, such as Fourier transformation-infrared spectroscopy and X-ray diffractometry, were also applied to interpret the results of thermal study of the products. [ABSTRACT FROM AUTHOR]

The interactions of CO with a high specific surface area tin dioxide was investigated by FTIR spectroscopy and thermogravimetric analysis. FTIR study of CO interactions have shown that CO can adsorb on cus (coordinatively unsaturated sites) Sn4+ cation sites (band at 2201 cm-1). In addition, CO reacts with surface oxygen atoms. This leads to the partial reduction of SnO2 surface and to the formation of ionised oxygen vacancies together with the release of free electrons, which are responsible for the loss of transmission. Formed CO2 can chemisorb on specific surface sites: on basic sites to form carbonates species and on acidic sites (Sn4+-CO2 species) which is in competition with the formation of Sn4+-CO species. TG experiment have shown that the reduction of SnO2 by CO at 400°C occurs in two steps. First, the reduction of SnO2 surface, which is a quick phenomenon. This has allowed to evaluate that more than 12% of reducible surface oxygens can react with CO, essentially because of the presence of a large amount of surface hydroxyl groups. The second step of the reduction of SnO2 would be the progressive reduction of SnO2 bulk by the slow diffusion of oxygen atoms from the bulk to the surface. [ABSTRACT FROM AUTHOR]