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1

Solution enthalpies of calcium fluorapatite in nitric acid and in pure water

Ardhaoui Kaouther

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 3

548--555

EN

In this study, the enthalpies of dissolution of the calcium fluorapatite Ca10(PO4)6F2 were measured in nitric acid solutions at various pH at 298.15 K with the aim of attaining the dissolution enthalpy in pure water which cannot be directly measured. Mechanisms of the reactions of dissolution involving Ca(NO3)2, Ca(H2PO4)2, CaHPO4, H3PO4,and HF entities were proposed at different pH ranges. The solution enthalpies of the products reactions were measured in the same solvent and temperature but at various pH values. When supported by the dissolution model of the calcium fluorapatite at various pH, the extrapolation of the solution enthalpies at pH=7 leads to the solution enthalpy of this apatite in pure water -275.1 kJ mol-1.

2

Flotation kinetics and thermodynamic behavior of chalcopyrite and pyrite in high alkaline systems

Yan H., Yuan Q., Zhou L., Qiu T., Ai G.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 3

901--910

EN

The monomineral flotation test and microcalorimetry were used to study the flotation kinetics and thermodynamic behavior of chalcopyrite and pyrite in high alkaline systems of lime and NaOH. The results showed that in these systems there were less hydrophilic substances on the chalcopyrite surface, so that the apparent activation energy of sodium butyl xanthate (SBX) adsorption on chalcopyrite surface was low. This promoted the adsorption of SBX and increased the flotation rate and recovery of chalcopyrite. In contrast, the hydrophilic Fe(OH)3 and SO42- formed by oxidation on the pyrite surface increased the adsorption activation energy of SBX. Thus, the flotation rate and recovery of pyrite were lower. Moreover, in the lime high alkaline system, the hydrophilic calcium film generated on the pyrite surface further hindered the adsorption of SBX, thereby further inhibiting pyrite in this environment. In other words, the lime high alkaline environment increased the apparent activation energy difference of SBX adsorption between chalcopyrite and pyrite compared to the NaOH system, facilitating the flotation separation of chalcopyrite and pyrite. The results can help with the theoretical research of flotation separation of other minerals, and provide guidance for developing low alkaline and lime-free pyrite depressants.

3

Wojciech Świętosławski - najwybitniejszy polski fizykochemik

Wacławek W., Wacławek M.

Chemistry-Didactics-Ecology-Metrology

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2007

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R.12, NR 1-2

43--50

PL

Przedstawiono życiorys i osiągnięcia Profesora Wojciecha Świetosławskiego, najwybitniejszego polskiego fizykochemika, zwłaszcza podkreślono jego wkład do termochemii. Profesor pokazał, że ciepła spalania węglowodorów alifatycznych są w przybliżeniu wielkościami addytywnymi. Zaproponował i wprowadził pierwszy międzynarodowy wzorzec fizykochemiczny - kwas benzoesowy. Substancja ta na mocy decyzji Międzynarodowej Unii Chemii Czystej i Stosowanej (IUPAC) została wzorcem ciepła spalania. Wynalazł on wiele przyrządów pomiarowych o dużej dokładności (adiabatyczne mikrokalorymetry, ebuliometry i kriometry). Niektóre z nich są nadal używane. Świętosławski wniósł bardzo duży wkład w badania dotyczące chemii węgla i koksu. Wiele opracowanych przez niego technologii zostało wdrożonych do praktyki przemysłowej. Wśród jego studentów i uczniów było w przyszłości wielu wybitnych profesorów.

EN

The biography and academic and scientific achievements of Professor Wojciech Świętosławski the most distinguish Polish physical chemist were presented. It was stressed his contribution to early thermochemistry. He showed that for aliphatic hydrocarbons the heat of combustion is an additive quantity and characterized thermochemically a number of chemical substances in terms of their molecular structure and chemical properties. Świętosławski proposed (it was introduced into practice by IUPAC) the first international physicochemical standard - benzoic acid, a standard of the heat of combustion. He invented many physicochemical Instruments of high accuracy (still used) eg. adiabatic microcalorimeters, ebulliometers and cryometers. The instrumentation was used by him and his coworkers to carry out much of outstanding basic and applied research. In the field of research important for industry one should stress his enormous contribution to chemistry of coal and coke formation process. Many of his invention have been introduced into industrial practice. Among his students and coworkers have been many in the future distinguish university professors.

4

Stability Analysis of n-Butyl-nitratoethylnitramine (Bu-NENA)

Wilker S., Gjersoe R., Stenslands P., Becher Ch.

Central European Journal of Energetic Materials

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2007

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Vol. 4, nr 3

59-80

EN

This article describes the thermal decomposition of n-Butyl-nitratoethylnitramine (Bu-NENA) which is a relatively new, not very widely used energetic plasticizer having attractive features. The decomposition reaction is a hydrolysis which leads to the formation of n-Butyl-ethanolnitramine (Bu-ENA) and nitric acid. stability of Bu-NENA can be measured by the Bu-ENA formation rate and by microcalorimetry. The stability of high quality material is good enough that a stabilizer is not necessarily needed. As the main reaction is forced by hydrolysis it is recommended that Bu-NENA is stored in dry conditions. Surprisingly DSC does not differentiate very well between stable and unstable samples. The main difference is found in the peak areas, not in the onset or peak maximum temperatures. decomposition product Bu-ENA is still an energetic material with an exothermic decomposition behaviour.

5

Activation Energy of Propellants at Low Temperature Range

Ticmanis U., Wilker S., Pantel G.

Central European Journal of Energetic Materials

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2006

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Vol. 3, nr 4

51-72

EN

This paper describes a new approach to determine the activation energy of propellant decomposition reactions which quantifies the temperature dependence of a reaction rate at temperatures below 50 C by using an indirect microcalorimetric method. Whereas the determination of life time and stability of propellants is usually performed by artificial ageing at elevated temperatures with a temperature range usually between 70 and 130 C only few and scattered data are available for temperatures below 50 C.Normally these activation energies for propellant decomposition reactions are not known below temperatures of about 50 C because (i) the reaction rates are very small and thus ageing times have to be very long and (ii) because of slow reactions the chemical change of the propellant becomes very small which - in combination with too short ageing times - may lead to wrong estimations and calculations. The main reason for this is that the experimental error is relatively big in comparison with the real change of the propellant.To be on the 'safe side' people usually assume a low value of activation energy. This has the effect that measuring times at high temperatures are much longer than they should be and that maybe good material is thrown away too early in fear of a thermal instability.To overcome this problem we have established a new approach by an indirect microcalorimetric method. This method evaluates the shift of typical points in the heat flow curve to earlier times after artificial ageing at relatively low (30-70 C) temperatures. From the time shift of a specific point in the heat flow curve (compared to the unaged material) and the temperature difference between ageing temperature and measuring temperature activation energies of the whole temperature range between 89 C and 30 C are available. We have verified the usability of this approach with six different nitrocellulose based propellants.

6

Surveillance of gun propellants ; microcalorimetry

Klerk W. de

Problemy Techniki Uzbrojenia

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2000

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R. 29, z. 73

27--28

EN

TNO-PML is assigned by the Netherlands MoD to perform the surveillance of gun propel/ants used by the Netherlands Forces. For nearly 30 years TNO is performing this task with a Heat Flow Calorimeter (HFC). From the heat generation a safe period is calculated. This technique is accepted by NATO and laid down in a STA NAG. At the moment TNO perform the surveillance of about 1200 different propellants, with about 400 tests each year.