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31.
Jaakko I. Partanen Pekka M. Juusola Pentti O. Minkkinen 《Journal of solution chemistry》2001,30(5):443-462
Equations were determined for the calculation of the stoichiometric (molality scale) dissociation constant Km of benzoic acid in dilute aqueous NaCl and KCl solutions at 25°C from the thermodynamic dissociation constant Ka of this acid and from the ionic strength Im of the solution. The salt alone determines mostly the ionic strength of the solutions considered in this study and the equations for Km were based on the single-ion activity coefficient equations of the Hückel type. The existing literature data obtained by conductance measurements and by electromotive force (EMF) measurements on Harned cells were first used to revise the thermodynamic value of the dissociation constant of benzoic acid. A value of Ka = (6.326 ± 0.005) × 10-5 was obtained from the most precise conductivity set [Brockman and Kilpatrick] and this value is supported within their precisions by the less precise conductivity set of Dippy and Williams and by the EMF data set measured by Jones and Parton with quinhydrone electrodes. The new data measured by potentiometric titrations in a glass electrode cell were then used for the estimation of the parameters of the Hückel equations of benzoate ions. The resulting parameters were also tested with the existing literature data measured by cells with and without a liquid junction. The Hückel parameters suggested here are close to those determined previously for anions resulting from aromatic and aliphatic carboxylic acids. By means of the calculation method based on the Hückel equations, Km can be obtained almost within experimental error at least up to Im of about 0.5 mol-kg-1 for benzoic acid in NaCl and KCl solutions. 相似文献
32.
33.
An integer a is said to be regular (modr) if there exists an integer x such that a
2
x≡a (mod r). In this paper we introduce an analogue of Ramanujan’s sum with respect to regular integers (modr) and show that this analogue possesses properties similar to those of the usual Ramanujan’s sum. 相似文献
34.
35.
Some analogues of smith's determinant 总被引:1,自引:0,他引:1
We calculate the determinants of the greatest common divisor (GCD) and the least common multiple (LCM) matrices associated with an arithmetical function on gcd-closed and lcm-closed sets. We also consider some unitary analogues of these determinants. 相似文献
36.
M. Pantsar-Kallio Pentti K. G. Manninen 《Fresenius' Journal of Analytical Chemistry》1996,355(5-6):716-718
ICP-MS is used as an element selective detector for chromium species in aquatic samples using a coupled columm system consisting of a cation guard column and an anion column. The effects of large concentrations of disturbing ions, like NO3–, Cl–, CO32– and SO42–, are discussed and the comparison with the use of different chromium isotopes for data acquisition is given. Quite low concentrations such as 100 mg/l of CO32–, 10 mg/l Cl– and even 5 mg/l SO42– can cause an overestimation of chromium if not properly resolved1995 / Accepted: 24 October 1995 相似文献
37.
Olaf Morgenstern Peter Richter Juha Rouvinen Pentti J. Mlknen Pirjo Vainiotalo Kari Hnninen Markku Ahlgrn Jouko Vepslinen 《Journal of heterocyclic chemistry》1991,28(4):1091-1097
The reaction of 3- and 4-aminoacetophenone with thiophosgene in a chloroform-water-calcium carbonate mixture at room temperature results in good yields of the related, known isothiocyanates. At first, however, we failed in all our attempts to produce 2-isothiocyanatoacetophenones with this reaction. Closer inspection of the reaction showed, that the product distribution depends upon the concentration of hydrogen ions pro-ducted and on the reaction time. When the reaction was followed with thin-layer chromatography, it was observed that the isothiocyanates formed first. In the further course of the reaction, they were converted to the 4-methylene-2-oxo-3,1-benzothiazines by the action of protons. The final products of the reaction were the 4-(3,1-benzothiazin-4-yl)-methylene-3,1-benzothiazines, formed from the monomer in a dimerization process. Depending upon the time the protons were removed from the reaction mixture, different products could be isolated. 相似文献
38.
Proper peer review and quality of published articles are often regarded as signs of reliable scientific journals. The aim of this study was to compare whether the quality of statistical reporting and data presentation differs among articles published in ‘predatory dental journals’ and in other dental journals. We evaluated 50 articles published in ‘predatory open access (OA) journals’ and 100 clinical trials published in legitimate dental journals between 2019 and 2020. The quality of statistical reporting and data presentation of each paper was assessed on a scale from 0 (poor) to 10 (high). The mean (SD) quality score of the statistical reporting and data presentation was 2.5 (1.4) for the predatory OA journals, 4.8 (1.8) for the legitimate OA journals, and 5.6 (1.8) for the more visible dental journals. The mean values differed significantly (p < 0.001). The quality of statistical reporting of clinical studies published in predatory journals was found to be lower than in open access and highly cited journals. This difference in quality is a wake-up call to consume study results critically. Poor statistical reporting indicates wider general lower quality in publications where the authors and journals are less likely to be critiqued by peer review. 相似文献
39.
Pentti Haukkanen 《Aequationes Mathematicae》2017,91(3):527-536
It is well known that Euler’s totient function \(\phi \) satisfies the arithmetical equation \( \phi (mn)\phi ((m, n))=\phi (m)\phi (n)(m, n) \) for all positive integers m and n, where (m, n) denotes the greatest common divisor of m and n. In this paper we consider this equation in a more general setting by characterizing the arithmetical functions f with \(f(1)\ne 0\) which satisfy the arithmetical equation \( f(mn)f((m,n)) = f(m)f(n)g((m, n)) \) for all positive integers m, n with \(m,n \in A(mn)\), where A is a regular convolution and g is an A-multiplicative function. Euler’s totient function \(\phi _A\) with respect to A is an example satisfying this equation. 相似文献
40.
Ultrasonically aided mineral processing technique for remediation of soil contaminated by heavy metals 总被引:1,自引:0,他引:1
Kyllönen H Pirkonen P Hintikka V Parvinen P Grönroos A Sekki H 《Ultrasonics sonochemistry》2004,11(3-4):211-216
In this study, power ultrasound was used as aiding method for the mineral processing technique, which have recently been developed for the remediation of soil contaminated by heavy metal containing bullets, their broken parts and alteration products. Power ultrasound was used to disperse the soil to remove metals and metal compounds from soil particle surfaces instead of attrition conditioning. The soil diluted with water was treated using 22 kHz ultrasound power of 100 W up to 500 W. The effect of different ultrasonic treatment time and pulsation of ultrasound were studied on the purity of sink and float fractions in heavy medium separation process, screen fractions, and mineral concentrates and tailings from flotation process. Ultrasound enhanced the remediation of soil fractions in all the studied cases. Optimisation of the ultrasonic power will be done in the continuation study. 相似文献