Traceability system for elemental analysis KIPPHARDT, Heinrich; MATSCHAT, Ralf; RIENITZ, Olaf ...
Accreditation and quality assurance,
03/2006, Letnik:
10, Številka:
11
Journal Article
Recenzirano
A complete metrological traceability system for measurement results of chemical analysis was set up. Core components are pure substances (national standards) characterised at the highest metrological ...level, primary solutions prepared from these pure substances and secondary solutions deduced from the primary solutions and intended for sale. The relative uncertainty of the element mass fraction of the primary substances and solutions is < 0.01 and < 0.05%, respectively. For the certification of transfer solutions and for stability testing, a precision measurement method for element contents has been developed by means of optical emission spectrometry (ICP OES) by which uncertainties between 0.1 and 0.05% can be achieved. The dissemination to field laboratories is effected with the aid of a calibration laboratory of the German Calibration Service (DKD) which certifies the element content of the secondary solutions with an uncertainty ≤ 0.3%. Calibration with these solutions enables the user to establish traceability of his measurement results to the International System of Units (SI). Currently, the system comprises Cu, Fe, Bi, Ga, Si, Na, K, Sn, W, and Pb.
We use the Clausius–Clapeyron equation to calculate third virial coefficients at low reduced temperatures. This procedure gives an alternative to predict third virial coefficients in a region where ...the third virial coefficient is difficult to measure. We compare the results of this method with published third virial coefficient data. Calculated third virial coefficients have average percentage deviations within 5% of the experimental values at reduced temperatures between 0.8 and 1.0.
Measurements of the critical propertiespc, ρc, andTcfor the pure substances CO2, CHF3, SF6, and for (CO2+ CHF3) and (CHF3+ SF6) were performed by observation of the critical opalescence in a static ...equilibrium cell. The experimental data were compared to values given in the literature. The experimental results for the binary mixtures are described by the Peng-Robinson equation of state, using only the experimental data for the critical pressure and the critical temperature of the pure components and of one mixture of nearly equal amounts of substance. For the binary systems investigated, this equation of state describes the critical loci, the vapour–liquid equilibrium, and the dependence of the supercritical density on temperature and pressure rather well.
Do You Speak Chemistry? Togni, Antonio
Chimia,
10/2023, Letnik:
77, Številka:
10
Journal Article
Recenzirano
Odprti dostop
This article is a broad personal reflection about the language of chemistry, deriving from decades of experience in both research and teaching. The three levels of thought as represented by the ...Johnstone triangle, a critical attitude towards systematic nomenclature, the concept of pure substance, and the central significance of structural formulas as the most prominent form of representation in chemistry, are the main topics discussed. The chemical transliteration of the Platonic solids is presented as a mean of expression unique to chemistry.
Do You Speak Chemistry? Togni, Antonio
Chimia,
10/2023, Letnik:
77, Številka:
10
Journal Article
Recenzirano
Odprti dostop
This article is a broad personal reflection about the language of chemistry, deriving from decades of experience in both research and teaching. The three levels of thought as represented by the ...Johnstone triangle, a critical attitude towards systematic nomenclature, the concept of pure substance, and the central significance of structural formulas as the most prominent form of representation in chemistry, are the main topics discussed. The chemical transliteration of the Platonic solids is presented as a mean of expression unique to chemistry.
•Connection between vapor pressure and Boltzmann distribution was established .•2.A general equation expressing the relation between vapor pressure and temperature for pure substances was ...proposed.•The proposed general equation can be used for expressing liquid vapor pressure within temperature in going from melting point to critical point.
Vapor pressure (P) data of pure substances in gas/solid-liquid equilibrium is important for scientific research and practical applications. Due to the large temperature range going from melting point to critical point, it is an impossible task to determine the P of a pure substance at each temperature point. Up to now, there is no general equation that can accurately describe the relation between temperature (T) and P for all pure substances. Utilizing Boltzmann distribution, we presented a general expression, ln P = a + bT + cln(T) + d(1/T), for the P of pure substances, that is, the P-T dependence is nearly exponential over the entire range of liquid and solid existence. Furthermore, on the base of above equation, we established a corrected general equation to express the liquid vapor pressure within temperature in going from melting point to critical point.
lnP=a+bT+cTT/Tb+d(ln(T))+f(ln(T))T/Tb+g(1/T)
The results show that the corrected equation has the advantages of universality, simplicity, and high calculation accuracy for the vapor pressure involving liquid simple substances, liquid inorganic and liquid organic compounds.
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The theory of differential equations is a powerful tool necessary for constructing mathematical models of various applied problems and their solution. The study and analysis of the general ...differential relations between the derivatives of the thermodynamic functions of substances is a new direction in the theory of their thermodynamic properties. This research is the development of thermodynamics associated with the establishment and use of differential equations. This paper presents two new thermodynamic relationships between thermal variables pressure, absolute temperature, and specific volume. They relate first-order partial derivatives with unmixed second-order derivatives for these variables. Revealing new general relations of thermodynamics made it possible to formulate and solve a number of problems, among which we can note: creation of algorithms for calculating second-order mixed derivatives for a given thermal equation of state; analysis of the features of the second mixed derivatives at the critical point of pure substance; investigations of the general thermodynamic equations with entropy. The procedure for establishing new equations is based on the use of a rigorous mathematical apparatus and Maxwell's differential equations. Therefore, they are of a general nature, that is, they are valid for any pure substance or any mixture of fixed composition. They are also applicable to any model of the equation of state of these substances. With a formal approach to the concept of the term "equation of state", the new relations themselves can be considered as the equation of state of substance. The obtained new relations can be used to develop the theory of the thermodynamic properties of substances. In particular, in this work it is shown that the ratios of two partial derivatives of pressure over the volume, which are zero critical conditions, have no singularities at the critical point itself
The COVID-19 pandemic, which has spread the world and our country, has negatively affected the field of education as well as affecting many areas of life. Due to the epidemic, schools were closed and ...distance education was started. One of the most important learning ways we will use to develop the attitude towards active learning in order to make the science lesson more effective and permanent during the pandemic is science activities. That’s why it is important to investigate the applicability of science activities in the home environment during the distance education period. The purpose of this research is to design and implement science activities that can be done at home during the COVID-19 pandemic. The participants of the research consist of 30 middle school students in the 7th-grade class who take science courses in Afyonkarahisar. In this process, experiments related to the subject were determined and students were asked to do these experiments at home with the available facilities. A 7-item interview form was prepared as a data collection tool. Semi-structured interviews were also conducted with the students. According to obtained the results; It has been reached that the students easily adapt the materials used in the laboratory at home. During the applying experiments of the relevant subject at home, they carried out the experiments with the help of their families, the experiments contributed them a better understanding of the subject, and they experienced more easily due to performing by themselves. However, it has also been observed that there are students who have difficulties in doing the experiments at home.
Descartes on Immortality and Animals Daniel, Stephen H.
The European legacy, toward new paradigms,
02/2024, Letnik:
29, Številka:
2
Journal Article
Recenzirano
For Descartes, our minds are not natural causes because they are not themselves objects; rather, they are the activities that identify objects. In short, they are our challenges to the natural order ...of things, both in how we adapt to novel situations (as exhibited in what has been called the "rational action test") and in how we respond in unexpected yet appropriate ways to linguistic cues (in the "language test"). Because these tests reveal ways in which our minds (as "pure," creative, willful, and immortal substances) introduce novelty into nature, we are not determined (as animals are) by other objects. That is, our rational or linguistic activities are challenges to the order of nature precisely because they are not part of, but rather constitute, nature. Accordingly, "real" (creative) speech is logically prior to finite differentiations and is not limited by laws of nature that constrain animal behavior.
