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171.
Phase transition of water restrained by curdlan suspension
annealed at a temperature from 20 to 110°C was investigated by differential
scanning calorimetry (DSC). The melting temperature of water restrained by
annealed curdlan discontinuously decreased at around 60°C, while the amount
of bound water calculated from enthalpy of melting increased at 60°C,
regardless of water content. Using a highly sensitive DSC, curdlan suspension
with various concentrations was studied. It was found that an endothermic
transition was observed at ca. 58°C in a wide range of concentrations.
The transition observed at 60°C is thermo-reversible and both temperature
and transition enthalpy are constant even after gel formation. Well equilibrated
suspension at a temperature lower than 60°C formed no gel. 相似文献
172.
W. Zielenkiewicz B. Golankiewicz G. L. Perlovich M. Koźbiał 《Journal of solution chemistry》1999,28(6):731-745
Solubilities of tricyclic analogs of acyclovir have been determined in water at 25, 35, and 45°C and in octanol, water-saturated octanol, and octanol-saturated water at 25°C. Octanol-water partition coefficients were determined at 25°C. Melting temperatures and molar enthalpies of fusion were measured. Activity coefficients in water, octanol, and in aqueous octanol solutions were determined and are discussed. The effect of hydrophilic and hydrophobic substituents in the tricyclic analogs on their thermodynamic properties are discussed. The standard Gibbs energy of transfer between the saturated phases were found to correlate with known values of the melting point of the solvents and the solubilities of the solute. For a number of the compounds examined, correlations between the minimum inhibitory concentration against the herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2), varicella-zoster virus (VZV), thymidine kinase-deficient (TK–) strains of VZV and
were established. Detailed conclusions have been derived concerning the relationships between the structure and the thermodynamic parameters of the compounds examined. 相似文献
173.
Mikkelsen Ø Skogvold SM Schrøder KH Gjerde MI Aarhaug TA 《Analytical and bioanalytical chemistry》2003,377(2):322-326
Evaluation of different solid electrode systems for detection of zinc, lead, cobalt, and nickel in process water from metallurgical nickel industry with use of differential pulse stripping voltammetry has been performed. Zinc was detected by differential pulse anodic stripping voltammetry (DPASV) on a dental amalgam electrode as intermetallic Ni–Zn compound after dilution in ammonium buffer solution. The intermetallic compound was observed at –375 mV, and a linear response was found in the range 0.2–1.2 mg L–1 (r2=0.98) for 60 s deposition time. Simultaneous detection of nickel and cobalt in the low g L–1 range was successfully performed by use of adsorptive cathodic stripping voltammetry (AdCSV) of dimethylglyoxime complexes on a silver–bismuth alloy electrode, and a good correlation was found with corresponding AAS results (r2=0.999 for nickel and 0.965 for cobalt). Analyses of lead in the g L–1 range in nickel-plating solution were performed with good sensitivity and stability by DPASV, using a working electrode of silver together with a glassy carbon counter electrode in samples diluted 1:3 with distilled water and acidified with H2SO4 to pH 2. A new commercial automatic at-line system was tested, and the results were found to be in agreement with an older mercury drop system. The stability of the solid electrode systems was found to be from one to several days without any maintenance needed. 相似文献
174.
Morita A 《Journal of computational chemistry》2002,23(15):1466-1471
The polarizability of a water molecule in liquid is evaluated via ab initio and density functional calculations for water clusters. This work has considerably improved our previous effort [J Chem Phys 1999, 110, 11987] to attain quantitative accuracy for polarizability. The calculations revealed that the water polarizability in the liquid is reduced from that in the gaseous phase by 7-9%. These results suggest significant implications for polarizable water models. 相似文献
175.
176.
催化褪色光度法测定微量锰(Ⅱ)的研究 总被引:6,自引:2,他引:6
本文研究在硫酸介质中,锰(Ⅱ)催化EDTA还原重铬酸银,而使之褪色的新指示反应。确定了催化褪色反应动力学条件,锰(Ⅱ)的浓度在0-0.4μg/ml范围内,工作曲线呈良好的线性关系,检测限为0.011μg/mL,该方法用于天然水及污水中锰的测定,获得满意结果。 相似文献
177.
J. J. Galán J. L. Del Castillo A. González-Pérez J. Czapkiewicz J. R. Rodríguez 《Journal of solution chemistry》2003,32(10):919-927
The density and ultrasound velocity of aqueous solutions of tetradecyltrimethylammonium nitrate were measured in the temperature range of 15 to 35°C in 5°C intervals. The concentration range covered the premicellar and micellar regimes. By assuming a pseudophase separation model for the micellar system, we applied the densitometric data to estimate the apparent molar volumes and the apparent thermal expansibility coefficients of the surfactant in monomeric and micellar forms. Ultrasound velocity and density data enabled us to estimate the isentropic compressibility of the surfactant in both forms. The results are compared with relevant literature data for alkyltrimethylammonium bromides. 相似文献
178.
水中矿物元素的ICP-MS分析 总被引:12,自引:0,他引:12
用ICP-MS对地下水、地表水和饮用水中的矿物元素进行了分析测定,实验证明用ICP-MS可以同时测定地下水,地表水和饮用水中矿物元素;该法灵敏度、精密度和准确度都能满足有关标准的要求,具有多元素同时分析,样品前处理简单,干扰少,测定快速,省事省力等优点。 相似文献
179.
180.
Felix Franks 《Journal of solution chemistry》1995,24(11):1093-1097
At a recent meeting of the International Symposium on Solution Chemistry I presented a paper dealing with aqueous solutions in which water was present not in excess but as one component of a supersaturated solution with polyhydroxy compounds. In response to a request from the Editor of this Journal I have submitted this article in which I outline my general interest in the subject and its importance as a new direction for solution chemists. 相似文献