The determination of the second dissociation constant of sulfuric acid

The second dissociation constant of sulfuric acid is determined in 1M NaClO₄ at 25°C using an electrochemical cell without liquid junction consisting of a glass and a perchlorate electrode. By taking into account the association between the Na⁺ and SO ₄ ^2– ions an average value of 0.0184±0.0005 is found using three different methods. This corresponds with an apparent acidity constant KA ₂ ^* of 0.095±0.003     

The second dissociation constant of sulfuric acid at various temperatures by the conductometric method

The thermodynamic second dissociation constant K₂ for sulfuric acid has been determined by conductivity measurements of aqueous sulfuric acid solutions at various temperatures. The data are treated by using two different methods developed with two independent assumptions due to Noyes et al. and Shedlovsky. Both methods require the knowledge of relevant ionic conductivities, which may be calculated from the Onsager limiting law. The values for K₂ obtained with these two methods show excellent agreement. The value of 0.0103 mol-L^–1 at 25°C agrees with the best literature value of 0.0102 mol-L^–1 within the experimental uncertainty, as also does the enthalpy of dissociation which is derived from the derivative of the temperature coefficient of K₂.     

The ferrocene analogues of salicylic acid and aspirin

The reaction of hydroxyferrocene with 2,3-dihydropyran gave (ferrocenyloxy)-2-tetrahydropyran which on lithiation gave the corresponding 2-lithiated ferrocene which was used to prepare 1-carboxy-2-hydroxyferrocene and 1-carboxy-2acetoferrocene.     

The value of the second dissociation constant of hydrogen sulfide

Summary We have determined the second dissociation constant of hydrogen sulfide in the temperature range 20–60°.     

Gel speciation studies-I The intrinsic dissociation constant of weakly acidic cation-exchange gels

The arid-dissociation properties of three weakly acidic cation-exchange gels, CM-Sephadex C-50-120, Biogel CM-2 and CM-Biogel A, have been studied. Each of the gels was equilibrated in sodium polystyrene sulphonate (NaPSS) solutions at three different concentration levels (0.1, 0.01 and 0.001M). The volume of the gels was measured as a function of a (their degree of neutralization), and C(p) (the NaPSS concentration); pH and pNa were also measured at each alpha-value. Intrinsic pK values of 3.25 and 4.55 have been found for CM-Sephadex C-50-120 and Biogel CM-2 respectively.     

Determination of the second acidity constant of luminol

The second acidity constant of luminol, determined by a graphical spectro-photometric method at 25.0°C and an ionic strength of 5.0, is pK_a,2 = 15.1. A method for purification of luminol is also given.     

流动注射化学发光法测定肉桂酸

碱性条件下,肉桂酸对Luminol-H2O2-纳米银化学发光体系有较强的增敏作用,据此,结合流动注射技术,建立了测定肉桂酸的新方法。该法线性范围为2.5×10-8～2.5×10-6mol/L,检出限为6.0×10-9mol/L,对1.0×10-7 mol/L的肉桂酸平行测定9次,相对标准偏差为2.5%。该法可用于尿液中肉桂酸的测定。     

The protective effect of salicylic acid on lysozyme against riboflavin-mediated photooxidation

Tridentate Schiff base (H(2)L) ligand was synthesized via condensation of o-hydroxybenzaldehyde and 2-aminothiophenol. The metal complexes were prepared from reaction of the ligand with corresponding metal salts presence of substituted pyridine in two different solvents (MeOH or MeCN). The ligand and metal complexes were then characterized by using FTIR, TGA, (1)H NMR and (13)C NMR spectroscopies. The FTIR spectra showed that H(2)L was coordinated to the metal ions in tridentate manner with ONS donor sites of the azomethine N, deprotonated phenolic-OH and phenolic-SH. Furthermore, substituted pyridine was coordinated to the central metal atoms. The thermal behavior of the complexes was investigated by using TGA method and dissociations indicated that substituted pyridine and ligand were leaved from coordination. This coordination of the metal complexes was correlated by (1)H NMR and (13)C NMR. Finally, electrochemical behavior of the ligand and a Ni(II) complex were investigated.     

化学发光法测定水杨酸

根据在硫酸酸性溶液中高锰酸钾能氧化水杨酸产生化学发光反应 ,而乙二醛的存在可使发光强度增强 ,建立了一种测定水杨酸的化学发光分析法 ,检出限为 8.0× 1 0 -6mol/L,线性范围为 4.0× 1 0 -3～ 6.0× 1 0 -5mol/L。该法巳用于样品复方苯甲酸醇溶液中水杨酸的测定。     

壳聚糖-g-水杨酸的合成

合成了壳聚糖-g-水杨酸,用1^H NMR,IR和热重分析等对结构进行了表征。接枝反应的最佳条件为：壳聚糖12．5mmol,n（水杨酸）：n（壳聚糖）=0．75,于55℃～65℃反应1h,水杨酸接枝率为20％。     

Reduced fluidity of dipalmitoyl phosphatidic acid membranes by salicylic acid

This paper presents DSC and NMR study of how the kerotolytic drug, salicylic acid (SA), affects the thermotropic and morphological behavior of a model membrane, dipalmitoyl phosphatidic acid (DPPA). The membrane-drug system has been studied in the multilamellar vesicular (MLV) and in the unilamellar vesicular (ULV) forms, for SA/DPPA molar ratios from 0 to 0.5. The mode of interaction of SA molecules with DPPA is similar in MLV and ULV. Chain-melting transition becomes sharper and shifts to higher temperatures in the presence of the drug, implying an enhanced co-operativity of the acyl chains. NMR and DSC data indicate that the drug molecules are located in the aqueous interfacial region neighboring the lipid headgroups. The membrane becomes more rigid in the presence of the drug molecules, due to a stronger interaction between the lipid headgroups leading to reduced permeability. ULVs are destroyed by even a short equilibration at room temperature, whereas prolonged equilibration of the MLV only leads to a slightly reduced interaction between the lipid headgroups due to sequestering of the drug molecules in the interfacial aqueous region.