The thermal stability of natural melanins from bovine eyes, black human hair and the hard core of banana peel, synthetic melanins obtained enzymatically or by autoxidation of various precursors, and chemically modified synthetic mclanins was studied by DSC and TG analysis. It was shown that the resistance of melanins to thermal degradation depends on their origin. Synthetic melanins were found to be more stable to thermal decomposition than natural melanins. Methylation of melanins caused a significant increase in thermal stability. The DSC curves of melanins reveal typical relaxation phenomena in the temperature range 293-413 K. It is generally believed that melanins

The precipitated acids, obtained by partial stepwise oxidation of Aleksinac (Yugoslavia) shale Kerogen, were studied by thermal analysis. Significant differences were observed in the weight loss and the shape of TG curves of precipitated acids from various degradation steps, indicating their structural differences and heterogeneity of the kerogen. The thermal curves of precipitated acids were found to consist of two distinct parts. From IR data Jt was found that the low-temperature part corresponded to thermal changes of aromatic, and the high-temperature part of aliphatic type structures. These results were in good agreement with chemical analysis (elemental analysis, atomic H/C ratio, total acidity) of the same acids.

Paper laboratory-produced from sepiolite, Goles-Serbia was studied to determine its sorption characteristics for nitric oxides, water vapor, and ammonia. The paper adsorbed high percentages of nitric oxides and ammonia was stoichiometrically chemisorbed on paper saturated with NO2 and H2O. Infrared spectroscopy showed that the sorption of nitric oxides and ammonia does not destroy the crystal lattice of sepiolite, which was confirmed by XRD-analysis. Sorption of both nitric oxides and ammonia occurred by zeolitic water inside the structural channels of sepiolite. Pressure swing adsorption (PSA) or temperature swing adsorption (TSA) cycles can be repeated many times, in the case of NOx and NH3.

The influence of some experimental parameters on the quantitative determination of specific heats by DSC is discussed. Conditions allowing measurement of the specific heat with a maximum relative error of 1.5 ~ are proposed. The specific heats of NaA zeolite, Cp -----0.227 __+ 0.003 cal.~ -1, and AgA zeolite Cp = 0.205 __+ 0.003 cal.~ -1 have been determined.Specific heat can be relatively simply determined by DSC. Scanning of an external standard (usually synthetic sapphire) and a sample is accompanied by the corresponding deflections from the base line. Taking into account the correction due to blank deflection amplitude, the amplitude to mass ratio yields the value of the specific heat Cp of the sample directly.A (sample) M (sapphire) Cp (sample) = A (sapphire) M (sample) 9 Cp (sapphire)Equation (1) is based upon the proportionality between the amplitude and mass values and includes no other parameters, either internal or external. However, as it has been pointed out [1][2][3] that in DTA analysis peak area is not a linear function of mass, it can be expected that (1) is not generally valid. With our measurements, the specific heat could not be determined by means of Eq. (1) with an error of less than 10 ~ when working with the generally proposed "reasonable" limit of 40 rag.In this paper, the effects of different parameters on the determination of Cp by DSC are examined in a similar way as was done by Berg and Egunov [4] for the heat of phase transitions in DTA. ExperimentalA Perkin-Elmer DSC-1B was used for C D determination. An aluminium sample pan of 5.7 mm diameter and average weight 26 mg was put into the holder, and heated uniformly from the lower side. The temperature of the holder was measured with a platinum resistance thermometer. The sample was put into the sample pan, which was closed; it was always subjected to the same pressure. By this means,

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The catalytic effect of indigenous minerals in the pyrolysis of Aleksinac (Yugoslavia) oil shale was studied in this paper. The substrates were prepared by gradual removal of the mineral constituents (carbonates, silicates, pyrite) and the free and bound bitumens. The substrates were analyzed by chemical methods, X-ray diffraction, porosimetry, thermal analysis, 13C NMR, and standard ASTM Micro Activity Test (MAT) designed for the investigation of cracking catalysts. The liquid pyrolysis products were analyzed by organic geochemical techniques as well. Based on the yields of gaseous and liquid products and the coke, conversion degrees, GC analyses (MAT parameters) and weight losses (TG parameter), the catalytic effect of indigenous mineral components in the pyrolysis of Aleksinac oil shale organic matter was found to be very low. The results suggested that principal organic matter changes should be attributed to thermal rather than to catalytic cracking.

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