有关溶液pH的计算

结合化学教学实践,探讨了酸、碱、盐、缓冲溶液及溶液稀释时pH的计算方法及规律。

石膏岩溶蚀与强度特性试验研究

石膏岩在工程中使用广泛,其具有特殊的物理化学性质,常引发工程问题,因此研究石膏岩的溶蚀特性以及溶蚀前后强度、塑性、脆性等性质变化显得尤为重要。通过室内溶蚀试验分析其溶蚀机理,利用电镜扫描观察其微观结构,分析强度劣化机理,并通过单轴压缩试验,研究石膏岩在不同溶液条件下的软化性质。结果表明,不同溶液对石膏岩的影响不同。以石膏岩浸泡在纯水中为参照,NaCl溶液促进石膏岩的溶蚀量,使试样的强度降低,为纯水溶蚀后试样强度的40%,塑性变强,脆性减弱;冰醋酸溶液减少石膏岩的溶蚀量,强度少许增加,塑性变弱,脆性变强;氢氧化钠溶液可与石膏岩发生反应生成氢氧化钙,因此在前期可促进石膏岩的溶蚀,后期生成较多的氢氧化钙络合物附着在岩样表面阻止石膏岩继续溶蚀并使其强度变大、塑性变强。微观电镜图片显示,不同溶液对石膏岩的溶蚀程度以氯化钠溶液最为严重,其次分别为纯水、冰醋酸溶液、氢氧化钠溶液。单轴压缩试验时声发射活动发生次数与溶蚀量相一致。

Effects of additives on zinc electrodeposition from alkaline zincate solution

The effects of additives on the surface and cross-sectional morphologies of zinc deposits on iron substrate from alkalinezincate solution were characterized by scanning electron microscope(SEM).The cathodic reaction mechanisms under variousconcentrations of additives were investigated using cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)techniques.It is found that with increasing the additive A content in the bath solution,the nucleation overpotential(NOP)value isobviously increased and the inhibition effect is strengthened.This may be mainly due to the adsorption of additive A on the cathodicelectrode surface,which can cover the active sites and block the discharge reduction.The results of EIS analysis indicate that therate-determining step of zinc electrodeposition process is changed from mixed control step into electrochemical reduction step in thepresence of additive A.However,any quantity of additive B has little effect on the NOP value and the inhibition effect is not obvious.Furthermore,addition of additive A and additive B at the same time displays the strongest inhibition effect and shows a strongsynergism because of their co-adsorption on the cathodic electrode surface.

Kinetics of Zn cathodic deposition in alkaline zincate solution

Kinetic parameters of the electrode reactions were measured by investigating steady-state current-potential behaviors. The Tafel slopes of cathodic and anodic processes are -0.113 8 V and -0.041 18 V, the anodic and cathodic apparent transfer coefficients are 0.519 3 and 1.435 2, respectively, and the stoichiometric number of rate-deterrnining step is 1. The theoretical kinetics equation of electrode reaction was deduced, from which the dynamic parameters can be calculated as follows： the cathodic and anodic Tafel slopes are -0.118 V and -0.039 4 V, respectively, consisting with the experimental values, Finally, the correctness of the mechanism was further demonstrated using apparent transfer coefficient according to the electrochemical dynamic equation of multi-electron reaction.

Wettability and surfactivity of sodium phosphate surfactants in strong alkali solutions

The wettability,surfactivity and the correlation between wettability and surfactivity of sodium diethylhexylphosphate,sodium diethylhexyl polyoxyethylene phosphate and their complex in NaOH solutions were studied.A complex alkali resistant phosphate surfactant with good permeability was prepared.The wettability of surfactants was investigated by measuring the immersion time,sinking time and capillary effects of nature cotton grey fabric in NaOH solutions.The surfactivity of the surfactants was characterized by measuring the surface tension.The effect of the complex on the surface appearance of cotton grey fabric was also investigated with a scanning electron microscope(SEM) .The results show that all the surfactants exhibit good wettability for cotton grey fabric in 0.5-5.0 mol/L of NaOH solutions,the complex system exhibits better wettability in 5.0-7.0 mol/L of NaOH solutions,in comparison with either corresponding single surfactant component employed,and wettability is well correlative with the surfactivities of the surfactant.SEM images indicate that the cotton grey fabric is well wetted by the alkaline surfactant solution and the quality of fabric is improved.

Comparison of dissolution profile characteristics of 11 berberine hydrochloride tablet brands in different dissolution media

Berberine hydrochloride is commonly used to treat bacterial dysentery,gastroenteritis and other diseases.Many manufacturers are available on the market today,while the production process and formulation are quite different,which may directly affect the therapeutic effect of the drug.To this end,11 different production producers of berberine hydrochloride tablets were collected according to the pharmacopeia berberine hydrochloride dissolution method(basket method).In addition the dissolution process was carried out in four elution media with different pH,and the difference was similar(f2).Factors were calculated to evaluate in vitro dissolution requirements,and in vitro dissolution of different manufacturers of berberine hydrochloride tablets was determined by high performance liquid chromatography(HPLC).The method was verified by linearity,precision,stability and robustness.Based on the f2 value,there was a significant difference in the dissolution behavior of the formulations of most berberine hydrochloride tablet brands.This research provided the basis for further in-depth research in the later period.Although the drug specifications(0.1 g)were the same,the dissolution curve was different.This phenomenon may be attributed to the fact that the excipients and crystal form of the tablets affected the release and dissolution of the tablets in vitro.