Checking of mathematical calculation methods for the determination of kinetic parameters from non-isothermal measurements by test functions

The applied computing programs are checked by means of test values from theoretical models. First-order kinetics, the Avrami equation and the 2-dimensional diffusion equation have been calculated as theoretical values. The computer calculation was carried out both for the total reaction and for individual reaction intervals.For the calculation of kinetic parameters and the distinction between the various models, in principle, the integral method should be used. The calculation does not give any answer to the question whether there exists another equation not involved in the models selected, which describes the processes better. If there is no indication of the reaction, it should first be checked by the differential method. The correlation coefficient does not allow the individual model equations to be distinguished with statistical significance.     

干水：从概念提出到实际应用

通过对干水的发展史考证可知，20世纪中期，科学家研制出一种由二氧化硅颗粒包裹着水滴的干性粉末并将其命名为“干水（Dry Water）”，但在很长的一段时间内并没有引起人们的关注。至21世纪初，关于干水形成机理和制备技术的一系列研究相继展开。随后，干水巨大的潜在应用价值备受人们关注，其在化妆品、水合物储气、催化剂、灭火剂等众多领域的应用得到了一定程度的开发。干水相关技术的发展会使化学物质的利用方式不断创新。干水的相关知识和发展史改变了人们对水的认识，并会成为化学教科书和百科全书的重要内容。     

Observation of ferrobielastic switching in langasite crystals under a uniaxial static pressure

Ferrobielastic switching is observed by measuring the change in the frequency of a compound acoustic cavity made from a langasite (La₃Ga₅SiO₁₄) single crystal, under uniaxial pressure. The effect is detected from the jump in the cavity frequency at the point of switching. In quartz the measured value of the pressure at the point of switching is found to be much higher, 740 MPa. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 5, 338–340 (10 September 1997)     

Kinetic analysis of additively overlapping reactions. Part 1. Description of an optimization method and its use for the separation of peaks

The determination of kinetic parameters for additively overlapping TG steps is possible only by fitting model equations (e.g., phase-boundary reactions) to the non-standardized weight step by means of non-linear optimization. A general condition of this procedure is the reproducibility of a conversion curve from a partial interval. Calculations carried out with theoretical and with erroneous values have shown that it is highly dependent upon the dispersion of the measured values and upon the position and length of the interval. In general, it is to be considered that the maximum must be involved in the evaluation. An increase in dispersion of the data can be compensated for by the evaluation of an enlarged partial interval.The findings obtained have been applied to the evaluation of additively overlapping reactions by the use of the procedure described. A general condition of a successful separation of the peaks is the existence of an overlapping-free interval including the maximum for only one of the overlapping partial reaction steps.     

Application of the generalized standard addition method to correction for the effects of peak overlap and intermetallic compound formation in potentiometric stripping analysis

Applications of the generalized standard addition method in potentiometric stripping analysis are presented. Accurate quantitative results can be obtained, even when the analytical signals are strongly affected by peak overlaps or by the formation of intermetallic compounds. The possibilities and limitations of the approach are discussed. An optimized experimental procedure for correction of the copper-zinc intermetallic interference is introduced.