Main Chemical Changes Research Articles

Effects of heating media on microstructure and chemical composition of heat-treated Pometia pinnata

Changes of microstructure, crystallization, chemical composition, and equilibrium moisture content (EMC) of heat-treated wood (HTW) were investigated to explore the effects of heating media (saturated steam, superheated steam, air) and heat treatment (HT) temperature on HTWs. The results showed that the saturated steam induced more severe cell wall destruction than the other two media. Although the porosity slightly increased with the increasing HT temperature, superheated steam and air HT still decreased the porosity compared to that of control, whereas saturated steam HT increased the porosity. The HT increased both relative crystallinity and crystal size of HTWs. The increasing HT temperature slightly increased the relative crystallinity but decreased the crystal size. The highest crystallinity (55.0%) was observed after saturated steam HT. Leaching led to the increase of crystal size of HTW treated in saturated steam (about 0.15 nm), while those treated in unsaturated steam and air decreased. The increase in relative amount of lignin and cellulose due to the hemicellulose degradation were the main chemical changes of HTWs. Further lignin condensation reaction only occurred after saturated steam HT. Although saturated steam HT induced increased porosity, its lowest EMC (5.91%) indicated the decrease of hydroxyl groups.

Evidence of Self-Association and Conformational Change in Nisin Antimicrobial Polypeptide Solutions: A Combined Raman and Ultrasonic Relaxation Spectroscopic and Theoretical Study

The polypeptide Nisin is characterized by antibacterial properties, making it a compound with many applications, mainly in the food industry. As a result, a deeper understanding of its behaviour, especially after its dissolution in water, is of the utmost importance. This could be possible through the study of aqueous solutions of Nisin by combining vibrational and acoustic spectroscopic techniques. The velocity and attenuation of ultrasonic waves propagating in aqueous solutions of the polypeptide Nisin were measured as a function of concentration and temperature. The computational investigation of the molecular docking between Nisin monomeric units revealed the formation of dimeric units. The main chemical changes occurring in Nisin structure in the aqueous environment were tracked using Raman spectroscopy, and special spectral markers were used to establish the underlying structural mechanism. Spectral changes evidenced the presence of the dimerization reaction between Nisin monomeric species. The UV/Vis absorption spectra were dominated by the presence of π → π* transitions in the peptide bonds attributed to secondary structural elements such as α-helix, β-sheets and random coils. The analysis of the acoustic spectra revealed that the processes primarily responsible for the observed chemical relaxations are probably the conformational change between possible conformers of Nisin and its self-aggregation mechanism, namely, the dimerization reaction. The activation enthalpy and the enthalpy difference between the two isomeric forms were estimated to be equal to ΔH1* = 0.354 ± 0.028 kcal/mol and ΔH10 = 3.008 ± 0.367 kcal/mol, respectively. The corresponding thermodynamic parameters of the self-aggregation mechanism were found to be ΔH2* = 0.261 ± 0.004 kcal/mol and ΔH20 = 3.340 ± 0.364 kcal/mol. The effect of frequency on the excess sound absorption of Nisin solutions enabled us to estimate the rate constants of the self-aggregation mechanism and evaluate the isentropic and isothermal volume changes associated with the relaxation processes occurring in this system. The results are discussed in relation to theoretical and experimental findings.

Detection of structural degradation of porcine bone in different marine environments with Raman spectroscopy combined with chemometrics

AbstractThe investigation of time since exposure and taphonomic alteration of bone in marine environments is crucial in forensic sciences. In this study, we explored the diagenetic changes to juvenile porcine bone in two different environmental marine contexts (submerged and intertidal) and how seasonal variation at time of deposition impacted on the pattern of taphonomic alteration in bone during early stages of exposure, from 6 to 24 weeks. The analysis was conducted using Raman spectroscopy combined with chemometrics. Principal component analysis of the Raman data of the recovered bones (either summer or winter season in 2014) showed that the main chemical changes occurred in the bioapatite (phosphate band, ν1(PO43−) at 961 cm−1) and organic constituents in the bones and depended on the exposure environment. Support vector machine (SVM) classification analysis classified the samples based on bone type, exposed environment and season, with high accuracy (>80%), but exposure time was less accurate (56%), although still higher than chance. When applying a SVM regression, time since exposure could be predicted with a ±5‐week uncertainty. This study illustrated the potential and limitations of using Raman spectroscopy to detect structural degradation of bone in different marine environments for forensic purposes.

Studies of drying curves for different vegetables in cabinet dryer

Drying has been applied to vegetables to preserve, store and transport food products. However, drying involves not only physical changes, easily detectable by the consumer through visual evaluation, but also chemical changes. These are not always visible, but are responsible for changes in color, taste and nutritional value, which compromise the overall quality of the final product. The main chemical changes associated with drying are related to the degradation of phytochemicals, such as vitamins, antioxidants, minerals, pigments and other bioactive compounds that are sensitive to heat, light and oxygen. Furthermore, nutrient losses are certainly associated with leaching following the removal of water from the vegetable during the drying process. In this study, different vegetables (purple cabbage, broccoli, mustard leaves, spinach leaves and bottle gourd) were dried in cabinet drier and their drying times were standardized. It was concluded from the experiment that 8, 9, 4, 3 and 7 hours drying time of vegetables will be appropriate in terms of color, nutrition and retention of nutrients.

Studying and imparting moisture absorption qualities of the new wood based bio-composite material

The paper reviews the method of creating a new bio-composite material based on birch wood and describes the mechanism of interaction of used motor oil with birch wood by infrared spectroscopy involved. It also provides data on the moisture absorption of the newly obtained composite. Used motor oil has high hydrophobic and antiseptic properties. The main chemical changes in oils occur as a result of its oxidation during engine operation under the temperature influence. However, the spectrum of spent engine oil is distinguished by the appearance of three new peaks: the wide peak of 3600-3000 cm−1, which is formed during characteristic vibrations of the OH group, indicating water cut in the engine oil, a narrow peak of 1740 cm−1, characteristic of stretching vibrations of the carbonyl group (C = O). In addition to these peaks, the other peak was detected at the 1150 cm−1 frequency and, yet, another weakly pronounced peak of 970 cm−1, which correspond to stretching vibrations of the peroxide group (C-O-O). The mechanism for impregnating wood with used engine oil has been developed. The moisture absorption of wood impregnated with spent engine oil is 3 times less than that of natural wood.

Changes in the Physical, Mineralogical and Geomechanical Properties of a Granitic Rock from Weathering Zones in a Tropical Climate

The changes in the composition and structure of the rock matrix caused by weathering lead to great alterations in its mechanical and physical properties. When considering this, geologists and engineers should pay special attention to materials from transition zones, namely, between the soil and rock over the weathering profiles. This research aimed to perform a wide characterization of the physical, mineralogical and geomechanical properties of a syenogranite rock in various degrees of weathering developed in a Brazilian tropical climate. Laboratory tests were performed to characterize the rock matrix properties at 5° of weathering. The mineralogical composition, the types and number of microstructures, the main physical and chemical changes, and the micropetrographic and microfracturing indexes of the matrix were obtained from analysing petrographic thin sections. The physical and geomechanical characterization included the determination of physical properties, index properties, strength and strain. The thin sections showed that the tropical climate had a great influence on the mineralogical changes, with the occurrence of mainly chemical processes from the medium to the highest degree of weathering. Among the properties evaluated, porosity was the most sensitive to the weathering, reaching 51 times higher in the highly weathered rock. The microfracturing index did not change much, showing a 42.0% increase from the low value of the fresh rock to the slightly weathered rock. Regarding the mechanical properties, the uniaxial compressive strength was the most sensitive to weathering, as observed by a loss of approximately 99.0% of its initial strength when in highly weathered rock conditions. In agreement with previous studies published on granites worldwide, the larger variations in the syenogranite rock properties were also presented from the medium degree of weathering. An experimental study on the use of Digital Image Correlation produced satisfactory results for determining the axial strain and elasticity modulus for more weathered syenogranite materials. New correlations and a quali-quantitative procedure for its classification have been proposed and tested based on the concepts of applicability, representativeness and significance. From 10 proposed correlations, 50% were considered with high or total applicability, and its use is highly recommended for estimating the parameters for syenogranite. Alternatively, from 31 correlations found in the literature, only 16% have shown high or total applicability for syenogranite.

Microstructure analysis and mechanical performance of crumb rubber modified asphalt concrete using the dry process

Globally, the vast majority of waste tires are landfilled, with catastrophic ecological consequences and in particular, serious threats to human health (e.g. fire, pests and soil contamination). Because of the increasing environmental awareness, the use of crumb rubber modified asphalt has become an important recycling strategy for waste tires. The so-called crumb rubber (CR), which is the recycled rubber from tires, has become a common additive in hot mix asphalt mixture due to its improvement of the mechanical performances of asphalt mixtures. The purpose of this study is to investigate the effect of adding crumb rubber to asphalt mixtures using the dry process by relating mechanical performances with microstructural characterizations. It was possible to observe the influence of conditioning process (time during which the asphalt mixture is kept at a high temperature after mixing) on the mechanical performance of the mixtures that depend primarily on the properties of the crumb rubber used. Specifically, it is shown that the conditioning time has an influence on the Marshall test results as well as the viscosity measurements. By using the Environmental Scanning Electron Microscope (ESEM), the distribution of the crumb rubber within the mixture has been investigated. In particular, the distribution of the crumb rubber by changing the conditioning time is of interest. The results showed that crumb rubber is well dispersed in the asphalt mixture when the conditioning time is increased. The effect of crumb rubber on the microstructure using Atomic Force Microscopy-Infrared Spectroscopy (AFM-IR) indicated that the main chemical change takes place in the para domain and catana or the so-called bee structures diminish on the CR modified bitumen as a consequence of more conditioning time.

Experimental and numerical investigation of CO2–brine–rock interactions in the early Palaeozoic mudstones from the Polish part of the Baltic Basin at simulatedin situ conditions

AbstractThis study discusses experiment‐induced alterations of shale rocks collected across the ordovician and silurian boundary at a potential site for carbon dioxide sequestration located in the Polish part of the Baltic Basin. Mudstone samples submerged in brine in custom‐built reactors were subjected to CO2 pressures of 30–35 MPa at a temperature of 80°C for 40 days. After the experiments were completed, the mineralogical composition of the studied rocks, their porosity characteristics, and chemistry of brines were analyzed and compared to the original compositions in order to detect experiment‐induced changes. Comparison of mineral composition before and after the experiments demonstrate a set of subtle but systematic mineral changes. The most conspicuous was a presence of Fe in the form of Fe‐oxyhydroxides that was related to the corrosion of the Fe‐bearing steel pipes supplying the experimental setup with CO2. This effect is important from the perspective of industrial carbon dioxide sequestration. However, the second source of Fe ions in experimental brines was related to the decomposition of chlorites, pyrite, and chloritized biotites. The suggested breakdown of pyrite is in line with the modification of the chemical composition of the experimental brines and observed transfer of S ions to the solution. The appearance of Mg and K ions in the experimental brines was related to the decomposition of chlorites and biotites. In turn, observed transfer of Sr cations to the solution could be attributed to the dissolution of biotites and K‐feldspars. The effects of analogue experiments were confronted with the results of geochemical modeling performed using the PHREEQC program. The numerical modeling not only allowed to reproduce all the main mineral and chemical changes postulated on the basis of our analogue experiment, but also enabled to put constraints on the time scale of occurring geochemical processes. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Roasting impact on the chemical and physical structure of Criollo cocoa variety (Theobroma cacao L)

AbstractThis work analyzed the effect of infrared roasting at 100, 150, and 200°C on the main physical and chemical changes of cocoa. Raw and roasted cocoa were analyzed using Brunauer–Emmett–Teller, Fourier transform infrared spectroscopy, modulated differential scanning calorimetry (MDSC), thermogravimetric analysis (TGA), SPME, and GC‐MS. Using MDSC, the fusion of fat at around 35°C, and the desolvation of water and volatile compounds were identified. TGA detected loss of mass of various groups of chemical compounds, including those present pre‐roasting and generated during roasting. The unroasted cocoa's total sugar content of 2.71% decreased to 0.64% when roasted at 200°C, whereas roasting at 200°C generated seven (7) pyrazines. Tetramethylpyrazine is the most abundant, reaching the highest concentration when roasted at 150°C, but decreases when roasted at 200°C, due to the high temperature. To obtain the maximum production of favorable pyrazines, the temperature must be controlled based on the quality objectives of the final product.Practical applicationsThe process of roasting cocoa is of great importance to the chocolate and derivatives industry. Knowledge of the chemical and physical changes that occur during roasting can help to optimize the operating conditions to obtain a better‐quality product, in particular by conserving and developing the flavor and aroma of fine Criollo cocoa varieties. This will support the industrialization of fine cocoas, presenting an option for improving the economic and social development of marginalized countries and communities.

Thermal Ageing Effects in a Commercial Three-Way Catalyst: Physical Characterization of Washcoat and Active Metal Evolution

The main system to reduce engine emissions of gasoline-fueled vehicles is represented by the three-way catalyst (TWC). The main catalyst of this system usually works in extreme conditions which induce a phenomenon called thermal ageing, the major way of catalyst deactivation. Increasingly stringent emissions standards require not only high efficiency in emissions abatement, but also maintaining the performances at high vehicle mileage. Automotive manufacturers need to accelerate testing methods and that should be representative of the ageing on vehicle, at the minimum expense in terms or time and cost. In order to develop and validate such methods, a deep understanding of all the microscopic processes associated with ageing is necessary. In this work we discuss a methodology for the study of the static thermal ageing of a commercial TWC. A specific washcoat extraction method was developed, and the separated washcoat was analyzed using XRD, TEM microscopy, Raman Spectroscopy and BET. These techniques allow to follow the main morphological and chemical changes in the sample: the loss of porosity, the evolution of crystalline phases and metal particles sintering and oxidation. The potential of Raman spectroscopy for the spatially resolved analysis of ageing is also highlighted. The results allowed to understand the process that involve the washcoat at high temperature.

A chemical evolution of NVP-containing VIPAR-family 3D polymer gel dosimeters – a brief overview

NVP-containing three-dimensional polymer gel dosimeters for radiotherapy dosimetry have been developed for more than 20 years. There have been 11 main modifications of the originally proposed VIPAR polymer gel dosimeter that altogether have amounted to 12 gel dosimeter formulae. This communication is to summarise the main chemical changes made to the VIPAR dosimeter over these years of research. The newest NVP-polymer gel dosimeters are also introduced.

Formulation of Multifunctional Materials Based on the Reaction of Glyoxalated Lignins and a Nanoclay/Nanosilicate.

Two organosolv lignins from different origins, namely, almond shells and maritime pine, were modified by using a nanoclay and nanosilicate. Prior to modification, they were activated via glyoxalation to enhance the reactivity of the lignins and thus ease the introduction of the nanoparticles into their structure. The lignins were characterized by several techniques (Fourier transformed infrared, high-performance size exclusion chromatography, 1H NMR, X-ray diffraction, and thermogravimetric analysis) before and after modification to elucidate the main chemical and structural changes. The reaction with glyoxal proved to increase the amount of hydroxyl groups and methylene bridges. This tendency was more pronounced, as the percentage of glyoxal was incremented. On the other side, the addition of the nanoclay and nanosilicate particles improved the thermal stability of the lignins compared to that of the original unmodified ones. This trend was more evident for the lignin derived from maritime pine, which displayed better results regarding the thermal stability, indicating a more effective combination of the nanoparticles in the lignin structure during the modification process.

Thermal and structural properties of magnesium tetraborate produced by solid state synthesis and precipitation for use in thermoluminescent dosimetry

Magnesium tetraborate is a phosphor with relevant characteristics for radiation dosimetry purposes. One of the main challenges on this material is still the understanding of its structure and luminescent processes involved in dosimetric performance. In this work, all the steps of the material production through DTA/TG, XRD and SEM techniques were evaluated to understand the main physical and chemical changes during the thermal process (calcination and sinterization) to produce the MgB4O7 samples. Two synthesis processes of MgB4O7 were studied: precipitation (P.S) and solid state (S.S). Finally, the luminescence efficiency of the pellets was investigated in function of different sintering temperatures. The initial stage of DTA/TG curves of the material just after the mixing of starting materials, regardless the synthesis, is marked by endothermic events caused by dehydration, decomposition of hydroxyl groups and hydrated borate phases. At higher temperatures, the curves are marked by exothermic events related to crystalline transitions, but the peak obtained for the S.S is better defined in comparison to P.S. Moreover, the DTA/TG analyses of the pellets prior and after the sinterization, showed that the process is more relevant for the MgB4O7 pellets produced by S.S (950 °C), dramatically reducing its higroscopicity. The SEM images reinforce the importance of the sintering process to create a resistant detector and with a more homogenous and cohesive surface, therefore increasing it luminescence properties. The thermoluminescent (TL) sensitivity of MgB4O7:Dy0,5% pellets produced via S.S, sintered at 950 °C, is 4 times higher compared to the ones sintered at 950 °C, via P.S. The materials produced via P.S did not present relevant changes in their TL sensitivity for sintering temperatures above 400 °C.

Discriminating five Polygonatum medical materials and monitoring their chemical changes associated with traditional process by FT-IR spectroscopy coupled with multivariate analysis

Several Polygonatum species are important medicinal materials as tonic to cure disorders in China. Because of their different medical effects, it is desired to distinguish them at species level. In addition, to ensure and control their medical quality, it is also important to monitor their chemical changes associated with traditional process. Taking the advantages of Fourier transform infrared spectroscopy (FT-IR) and multivariate analysis, we developed a convenient, fast and reliable approach to discriminate and quality control these materials. Despite similar absorption patterns, each species also presented spectral differences, especially on the FT-IR fingerprint range of 1800-600 cm−1. Second derivative method obviously enlarged those differences and then showed more species-specific features. These spectral differences could be used as powerful discriminating points to distinguish them. PCA results showed that each species separated clearly with their biological replicates grouped together, which indicated that the variance between species is greater than within species, therefore, these species could be distinguishable. Using this approach, the five herbal materials were discriminated successfully in their raw, processed and ethanol extracted formats. On the other hand, visual inspecting infrared spectra of samples from 1 to 9 process steps, absorbance near 1737, 1259, 817 and 780 cm-1 increased gradually but decreased gradually at 927 cm−1. Besides, spectral contour near 1050 cm−1 changed sharply with process treatment. These spectral changes indicated that hydrolyzing polysaccharides into oligo- and mono-saccharides, especially glucose and fructose, are the main chemical changes associated with traditional process. This is consistent with the traditional experience that the processed materials are dark as night and sweet as malt sugar. Meanwhile, our results also indicated that their chemical constituents changed profoundly after process, which might be the chemical basis for raw and processed materials have different medical effects. Based on absorbance at 817 and 780 cm−1 and the color, taste, smell of processed materials followed by energy efficacy, raw materials had to be processed more than 21 h to ensure their quality. This research shows the potential of FT-IR spectroscopy coupled with multivariate analysis to discriminate different herbs and to monitor chemical changes with process and then control their quality. This could be very helpful to ensure the quality, safety, and efficacy of herbs on clinical practices.

Effect of Thermal Aging on the Electrical Characteristics of XLPE for HV Cables

This work highlights the effect of thermal aging on the commonly studied electrical properties of cross-linked polyethylene devoted to be used in the HV cables insulation. The obtained results show the great effect of thermal aging on the electrical properties of the polymer especially for aging temperatures situated above the melting temperature of the material. On the other part, it is believed that the degradation degree is related to the applied temperature. Hence, the degradation process has been occurred in fast way as the temperature is higher. The almost deterioration markers in the dielectric behavior can be attributed to both the chemical and physical changes. The main chemical changes are the bulk thermo-oxidation degradation leading to the enhancement of dipoles and carbonyl groups concentration which disturbs the dielectric properties leading to the failure of the material. The physical changes result from the changes in the ratio of crystalline to amorphous parts in the material. Both changes have something to do it together in the life time reduction of the XLPE insulation.

Surface chemistry changes and microstructure evaluation of low density nanocluster polyethylene under natural weathering: A spectroscopic investigation

Polyethylene is the most commonly used plastic in daily life, covering wide areas of application e.g. this polymer is used as a greenhouses covering material. This article investigates the effect of photo-oxidation on commercial unstabilised Low Density Polyethylene (uLDPE), as result of outdoor weathering factors. In this study, the samples were exposed for four months to the natural weather. The physico-chemical effects of natural ageing were studied by attenuated total reflection Fourier transform infrared (ATR-FTIR) and X-ray photoelectron (XPS) spectroscopy to elucidate the chemical composition, the nature of chemical bonds established and further to interrogate the changes that occur on the surface of the uLDPE samples. The main chemical change of uLDPE results in the formation of different kinds of carbonyl and vinyl groups identifiable in the ATR-FTIR and XPS spectra. The degree of crystallinity for these samples was calculated in terms of time exposure. An increase in the degree of crystallinity due to chemicrystallization was observed, which we indicative of the occurrences of chain scission. During outdoor exposure it was found that the photo-oxidation results in the formation of chain scission occurrences via Norrish type II reactions.

P.4.c.001 - Common neurotransmission recruited in (R,S)-ketamine and (2R,6R)-hydroxynorketamine-induced sustained antidepressant-like effects

Several Polygonatum species are important medicinal materials as tonic to cure disorders in China. Because of their different medical effects, it is desired to distinguish them at species level. In addition, to ensure and control their medical quality, it is also important to monitor their chemical changes associated with traditional process. Taking the advantages of Fourier transform infrared spectroscopy (FT-IR) and multivariate analysis, we developed a convenient, fast and reliable approach to discriminate and quality control these materials. Despite similar absorption patterns, each species also presented spectral differences, especially on the FT-IR fingerprint range of 1800-600 cm−1. Second derivative method obviously enlarged those differences and then showed more species-specific features. These spectral differences could be used as powerful discriminating points to distinguish them. PCA results showed that each species separated clearly with their biological replicates grouped together, which indicated that the variance between species is greater than within species, therefore, these species could be distinguishable. Using this approach, the five herbal materials were discriminated successfully in their raw, processed and ethanol extracted formats. On the other hand, visual inspecting infrared spectra of samples from 1 to 9 process steps, absorbance near 1737, 1259, 817 and 780 cm-1 increased gradually but decreased gradually at 927 cm−1. Besides, spectral contour near 1050 cm−1 changed sharply with process treatment. These spectral changes indicated that hydrolyzing polysaccharides into oligo- and mono-saccharides, especially glucose and fructose, are the main chemical changes associated with traditional process. This is consistent with the traditional experience that the processed materials are dark as night and sweet as malt sugar. Meanwhile, our results also indicated that their chemical constituents changed profoundly after process, which might be the chemical basis for raw and processed materials have different medical effects. Based on absorbance at 817 and 780 cm−1 and the color, taste, smell of processed materials followed by energy efficacy, raw materials had to be processed more than 21 h to ensure their quality. This research shows the potential of FT-IR spectroscopy coupled with multivariate analysis to discriminate different herbs and to monitor chemical changes with process and then control their quality. This could be very helpful to ensure the quality, safety, and efficacy of herbs on clinical practices.

A simple and rapid infrared-assisted self enzymolysis extraction method for total flavonoid aglycones extraction from Scutellariae Radix and mechanism exploration.

A new, simple, and fast infrared-assisted self enzymolysis extraction (IRASEE) approach for the extraction of total flavonoid aglycones (TFA) mainly including baicalein, wogonin, and oroxylin A from Scutellariae Radix is presented to enhance extraction yield. Extraction enzymolysis temperature, enzymolysis liquid-to-solid ratio, enzymolysis pH, enzymolysis time and infrared power, the factors affecting IRASEE procedure, were investigated in a newly designed, temperature-controlled infrared-assisted extraction (TC-IRAE) system to acquire the optimum analysis conditions. The results illustrated that IRASEE possessed great advantages in terms of efficiency and time compared with other conventional extraction techniques. Furthermore, the mechanism of IRASEE was preliminarily explored by observing the microscopic change of the samples surface structures, studying the main chemical compositions change of the samples before and after extraction and investigating the kinetics and thermodynamics at three temperature levels during the IRASEE process. These findings revealed that IRASEE can destroy the surface microstructures to accelerate the mass transfer and reduce the activation energy to intensify the chemical process. This integrative study presents a simple, rapid, efficient, and environmental IRASEE method for TFA extraction which has promising prospects for other similar herbal medicines. Graphical Abstract ᅟ.

An investigation of accelerated temperature-induced ageing of four wood species: colour and FTIR

The study investigated and compared the behaviour of four wood species, originating from Europe and China, in terms of temperature-induced artificial ageing. It was conducted at 100 °C for a total period of 288 h. Ageing effects were evaluated by colour measurements in the CIE Lab system and by FTIR analysis. Colour changes were then related to chemical changes in the wood. The investigated wood species were European ash (Fraxinus excelsior), European walnut (Juglans regia), Chinese ash (Fraxinus mandshurica) and Chinese walnut (Juglans mandshurica). Colour changes were maximum for European ash and minimum for Chinese ash, while European walnut and Chinese walnut evolved quite similarly. Main chemical changes due to temperature ageing were reduction of hydroxyl groups, increase of the unconjugated carbonyl groups and an apparent slight increase of lignin, more evident for European ash and delayed for European walnut. Formation of aromatic carbonyl conjugated groups as quinoid structures as a result of oxidative reactions was revealed especially for European ash. The different behaviour of the studied wood species may be explained by their different chemical composition, especially hemicelluloses, lignin and extractives content.

Kayrobertsonite, MnAl2 (PO4)2 (OH)2·6H2 O, a new phosphate mineral related to nordgauite

Kayrobertsonite, MnAl 2 (PO 4 ) 2 (OH) 2 ·6H 2 O, is a new secondary phosphate mineral from the Hagendorf Sud pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany and the Foote Lithium Company mine, Kings Mountain district, Cleveland County, North Carolina, USA. Kayrobertsonite crystals occur as intergrown masses of snow-white, soft, finely fibrous needles, less than 5 μm in diameter and no more than 100 μm in length. Quantitative analysis of Foote mine kayrobertsonite gave the empirical formula: Mn 0.97 Ca 0.03 Fe 0.02 Al 1.87 (PO 4 ) 2 (OH) 1.62 F 0.03 (H 2 O) 0.38 ·6H 2 O; and for Hagendorf Sud kayrobertsonite: Mn 0.92 Ca 0.06 Fe 0.02 Al 1.87 (PO 4 ) 2 (OH) 1.19 F 0.42 (H 2 O) 0.39 ·6H 2 O. Foote mine kayrobertsonite crystals are biaxial (−), with indices of refraction α = 1.530(1), β = 1.554(1), γ = 1.566(1), measured in white light; 2 V (meas.) is 70.3(5)°, while 2 V (calc.) is 69.6°. The mineral is nonpleochroic. The orientation of the crystals is Z ≈ c (length slow). Kayrobertsonite is triclinic, space group P 1 ¯ , with the unit-cell parameters: a = 10.049(2), b = 10.205(2), c = 6.083(1) A, α = 91.79(3), β = 99.70(3), γ = 98.02(3)°, V = 607.9(2) A 3 and Z = 2 (Foote mine). The polyhedral framework in kayrobertsonite has the same topology as that in nordgauite, but with replacement of F by OH at the bridging anion sites. The main crystal chemical change from nordgauite to kayrobertsonite is a doubling of the number of water molecules in the [001] channels.