盐卤硼酸盐化学 Ⅻ. MgO·3B2O3·7H2O的热行为和脱水动力学

通过对合成MgO·3B2O₃·7H₂O的热分析研究确定热脱水反应的阶段、温度和产物,给出脱水过程的热化学反应方程式.利用甲醇、水与三氧化二硼之间的酯化反应进行相分离,确定该化合物高温结晶化产物的物相组成为晶态六硼酸镁(2MgO·3B₂O₃)和无定形B₂O₃.对该化合物的TG和DTG数据进行处理结果,给出了相应的非等温热脱水反应动力学方程.     

Cyclodextrins with heterocyclic substitution as GC stationary phases

Summary Two new cyclodextrin (CD) derivatives, heptakis{2,6-di-O-pentyl-3-O-[3′-(2″-chloro-4″,5″-dioxylmethene)-phenyl-5′-iso-oxazolylmethyl]}-β-CD (CD I) and heptakis{2,6-di-O-methyl-3-O-[3′-(2″-chloro)-phenyl-5′-iso-oxazolylmethyl]}-β-CD (CD II) were synthesized and coated on fused-silica capillary columns. Their chromatographic characteristics, including column efficiency, polarity, selectivity and phase transition were studied and compared with similar β-CD stationary phases. It was found that the heterocycle group has a significant effect on the selectivity of the CD stationary phases. Both stationary phases can be successfully used to separate many di- and trisubstituted benzene positional isomers and show stronger separation ability in separating low-polarity benzene positional isomers than other β-CD stationary phases.     

On the interaction of solitons for a class of integrable systems in the spacetime R n+1

A class of integrable systems of nonlinear partial differential equations in the spacetime R ⁿ⁺¹ is introduced. Single and multi-soliton solutions are constructed by using the Darboux matrix method. It is proved that as t±, a k multi-soluton solution splits asymptotically into k single solitons. Moreover, the interaction between solitons is elastic if we consider their magnitudes only.The work is C. H. Gu supported by the Chinese National Program for fundamental research nonlinear science.     

Large third-order nonlinear optical properties of C70 fullerene in the infrared regime

The nonlinear third-order optical susceptibility of C₇₀ in a toluene solution is measured for the first time by the method of degenerate four-wave mixing using 10 ns laser pulses at 1.06 m. The third-order susceptibility X _in ⁽³⁾ is 5.6×10^–12 esu for a C₇₀ toluene solution at a concentration of 0.476 g/l. The correspondent magnitude of the hyperpolarizability ₁₁₁₁ of the C₇₀ molecule is 1.2×10^–30 esu which is in a good agreement with the prediction given by the model of a free electron in a spherical box.     

Determination of methylmercury fluxes across the air–water and air–soil interfaces by gas chromatography with electron capture detection

A method for the determination of methylmercury (MeHg) fluxes across the air–water and air–soil interfaces was developed using an in situ chamber. The MeHg in the air coming out of the chamber was captured by a column containing sulfhydryl cotton fiber adsorbent. MeHg was then desorbed from the column by using 2 mol L^–1 HCl. The MeHg in the effluent was extracted with benzene, and determined by gas chromatography with electron capture detection. Finally, the MeHg flux was calculated using the chamber. The method was applied to simulated experiments, and the results showed that the MeHg fluxes in the air–water system were higher than those in the air–soil–water system. The method was also successfully applied to the field measurements of an environment polluted by a chemical factory, and the results showed that the MeHg fluxes across the air–soil and air–water interfaces were 0.21–3.09 and 0.14–0.79 ng m^–2 h^–1, respectively. The method will be a useful tool in the environmental study of MeHg.