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A Practical Guide to FT-IR Photoacoustic Spectroscopy
Published in Patricia B. Coleman, Practical Sampling Techniques for INFRARED ANALYSIS, 2020
J. F. McClelland, R. W. Jones, S. Luo, L. M. Seaverson
Many samples have moisture contamination which will cause the presence of water vapor in the detector’s sample chamber and the appearance of water vapor absorbance bands in spectra. A desiccant for water vapor reduction can be put into a large stainless steel cup (as shown in Figure 7) which is placed in the sample holder underneath the sample cup. Figure 8 shows a large cup with polymer pellets which is placed above the desiccant cup. As mentioned in Section III. A., magnesium perchlorate is a very effective desiccant. Water vapor can be eliminated with the combination of purging the detector with dry helium, allowing adequate time for the desiccant to work, and minimizing the amount of sample in the cup. Use only enough material to cover the bottom of a small cup if water vapor is a problem. When not in use, desiccant should never be left in cups open to room atmosphere because moisture from the room will collect in the desiccant and form a corrosive liquid.
Ignition of Dusts
Published in John Nagy, Harry C. Verakis, Development and Control of Dust Explosions, 2017
The effect on layer ignition temperature by adding an oxidizing agent to a combustible dust is not conclusive. When magnesium perchorate was mixed with wood flour, the ignition temperature decreased from 250°C to 210°C. With 20% magnesium Perchlorate, a violent ignition occurred and, with 50%, an explosive reaction occurred. The addition of various percentages of potassium dichromate and sodium nitrate did not materially affect the layer ignition temperature of the wood flour. The addition of potassium permanganate to the wood flour resulted in a lowering of the ignition temperature to 215°C.
An amino acid@isopolyoxometalate nanoparticles catalyst containing aspartic acid and octamolybdate for the synthesis of functionalized spirochromenes
Published in Inorganic and Nano-Metal Chemistry, 2021
Majid Momahed Heravi, Tayebeh Momeni, Masoud Mirzaei, Vahideh Zadsirjan, Morteza Tahmasebi
Spiro[2-amino-4H-pyran-oxindole] derivatives have been synthesized via three-component condensation reaction comprising, isatin, malononitrile, and β-dicarbonyl compounds including barbituric acid, dimedone, or hydroxycoumarin. This condensation has been accomplished in electrocatalytic method[30] as well as being promoted by a number of catalysts such as TEBA (triethylbenzyl-ammonium chloride),[31] InCl3-SiO2,[32] NH4Cl,[33] nano MgO,[34] (SB-DBU)Cl,[35] [BMIm]BF4,[36] sodium stearate,[37] ethylenediaminediacetate,[38] alum,[39] SBA–Pr–NH2,[40] magnesium perchlorate,[41] mesoporous silica nanoparticles,[42] β-cyclodextrin,[43] L-proline,[44] and silica sulfuric acid magnetic nanoparticle.[45]
Characterisation of methane sources in Lutjewad, The Netherlands, using quasi-continuous isotopic composition measurements
Published in Tellus B: Chemical and Physical Meteorology, 2020
Malika Menoud, Carina van der Veen, Bert Scheeren, Huilin Chen, Barbara Szénási, Randulph P. Morales, Isabelle Pison, Philippe Bousquet, Dominik Brunner, Thomas Röckmann
The isotope measurement system is based on a continuous flow isotope ratio mass spectrometry (CF-IRMS) system. One IRMS instrument (Thermo Delta Plus XP, Thermo Fisher Scientific Inc., Germany) was used to measure alternatively 13C-CO2 and 2H-H2. Before injection into the mass spectrometer, CH4 needs to be isolated from the other air components and converted to CO2 or H2. To extract the CH4, ambient air is first pumped through magnesium perchlorate, a drying agent. Then, the dry air is sent through two successive cryogenic traps, cooled to −120 °C and filled with HayeSep D in the center and glass beads on each end. The cooling is achieved by a Polycold compact cooler compressor (Brooks Automation Inc., USA), filled with coolant PT-30. The cold end is attached to a copper block on which the traps are mounted. The traps are kept under vacuum to avoid condensation of water and to allow a fast and precise temperature control of each of them. The methane is released by heating the traps to −45 °C, and then it is converted to CO2 and H2 in combustion and pyrolysis furnaces, at temperatures of 1150 and 1350 °C, respectively. CO2 is further purified on a gas chromatography (GC) column, at a temperature between 0 and 10 °C. The whole extraction process is illustrated in Fig. S1, and described in more detail in Röckmann et al. (2016). A picture of the extraction system installed at Lutjewad is shown in Fig. S2.
Biomolecular self-assembly under extreme Martian mimetic conditions
Published in Molecular Physics, 2019
Harrison Laurent, Alan Soper, Lorna Dougan
These ions also act to perturb water structure [26–29] and therefore are likely to perturb hydrogen bonding. Mg(ClO4)2 does this particularly effectively and is capable of compressing water structure in a manner similar to the formation of ice VII at room temperature, corresponding to an external pressure of approximately 3 GPa [30,31]. This phenomenon leads us to ask the question: how does the presence of Mg(ClO4)2 affect the hydration and association of biological molecules in water? This is investigated at a near eutectic [7] magnesium perchlorate concentration and using glycine as a model amino acid due to its molecular simplicity, high solubility [32], and previously recorded presence in astronomical environments [33–35]. Data was collected using neutron scattering with isotopic substitution at 25°C and −20°C and analysed using empirical potential structure refinement (EPSR) [36–38] to yield a simulated box of atoms consistent with the scattering data. These two temperatures were chosen as they are between the freezing temperature of eutectic NaCl solution and the bubble temperature of eutectic NH3 solution, as these will be the subject of future investigations. It is found that while magnesium perchlorate disrupts the hydrogen bonding ability of the amino acids, they are still able to cluster, and that this clustering is temperature dependent.