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The thermal decomposition of magnesium peroxoborate was studied by means of a derivatograph. It was found that the decomposition involves a sequence of reactions: dehydration and O2 evolution. The kinetic parameters were obtained in each step of the reaction. The thermal stabilities of three kinds of metal peroxoborates are discussed.

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Abstract  

Samples of hair from 370 subjects were analysed by neutron activation. The samples were taken from residents of nine different countries: Japan, France, Ivory Coast, Brasil, Paraguay, Canary Islands, Papua New Guinea, Italy and New Zealand. The selenium determination was made using the76Se(n,)77mSe reaction.It was found that the average selenium concentration in the hair of Japanese subjects, both those living in Japan and those living in foreign countries was higher (total average: 0.59±0.14 mg/kg) than those of subjects from other countries (total average: 0.42±0.13 mg/kg).Our results from the determination of the selenium concentration in the hair of individuals from different countries show significant differences between different countries, nevertheless, the selenium content in human hair was small amounts. Since this is likely due to differences in diet. This method was able to analyze quickly for many samples.

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Journal of Thermal Analysis and Calorimetry
Authors:
T. Nagaishi
,
S. Ishiyama
,
J. Yoshimura
,
M. Matsumoto
, and
S. Yoshinaga

The reaction between ammonium sulphate with aluminium oxide was studied. It was confirmed by X-ray diffraction and chemical analysis that three intermediate reaction products, (NH4)3Al(SO4)3, NH4Al(SO4)2 and Al2(SO4)3, are formed. The thermal decompositions of these three compounds were carried out. It has been shown that the same rate law is valid for them. The activation energies for (NH4)3Al(SO4)3, NH4Al(SO4)2 and Al2(SO4)3 are 95.9, 177.9 and 291.0 kj/mol, respectively.

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Summary Heat capacity measurements of the two-dimensional metal-assembled complex, (NEt4)[{MnIII(salen)}2FeIII(CN)6] [Et=ethyl, salen= N,N’-ethylenebis(salicylideneaminato) dianion], were performed in the temperature range between 0.2 and 300 K by adiabatic calorimetry. A ferrimagnetic phase transition was observed at T c1=7.51 K. Furthermore, another small magnetic phase transition appeared at T c2=0.78 K. Above T c1, a heat capacity tail arising from the short-range ordering of the spins characteristic of two-dimensional magnets was found. The magnetic enthalpy and entropy were evaluated to be ΔH=291 J mol-1 and ΔS=27.4 J K-1 mol-1, respectively. The experimental magnetic entropy agrees roughly with ΔS=Rln(5·5·2) (=32.5 J K-1 mol-1; R being the gas constant), which is expected for the metal complex with two Mn(III) ions in high-spin state (spin quantum number S=2) and one Fe(III) ion in low-spin state (S=1/2). The heat capacity tail above T c1 became small by grinding and pressing the crystal. This mechanochemical effect would be attributed to the increase of lattice defects and imperfections in the crystal lattice, leading not only to formation of the crystal with a different magnetic phase transition temperature but also to decrease of the magnetic heat capacity and thus the magnetic enthalpy and entropy.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
T. Tanaka
,
M. Mukai
,
T. Maeda
,
J. Matsumoto
,
H. Ogawa
,
Zhentang Li
,
Xudong Wang
,
Zhiwen Fan
,
Liangtian Guo
, and
Cunli Liu

Abstract  

Migration experiments with 237Np(V) and 241Am(III) have been performed using a column system, packed with loess, taken from Shanxi, China. The adsorption mechanism of 237Np and 241Am on the loess was examined by a chemical extraction method. Most of 237Np was adsorbed on the influent edge of the column, and the adsorbtion was mainly controlled by surface complexation. However, the migration of 237Np in loess media could be roughly evaluated by the distribution coefficient. In the case of 241Am, particulate, the 241Am species was formed in the influent solution and moved in the column. The 241Am adsorbed on loess was controlled by irreversible reactions. The migration behavior of particulate 241Am in loess media could be expressed by the filtration theory.

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