Conductivity of Sodium Chloride in Water + 1,4-Dioxane Mixtures from 5 to 35°C II. Concentrated Solution

Conductivity data of sodium chloride in binary mixtures of water and 1,4-dioxanefrom 5 to 35°C were measured, covering an electrolyte concentration range upto the limit of solubility in the solvent mixtures and up to 5 mol-dm^–3 inpure water. Data analysis is based on the mean spherical approximation (MSA).Comparison is made with the data representation by the empirical Casteel-Amisequation. The association constants of the MSA are compared with those fromchemical model calculations at low concentrations (lcCM).     

Diffusion of ionic species labeled with35S in various aqueous electrolyte solutions at 25°C

Composite diffusion coeffcients have been measured for the various species labeled with³⁵S which are present in a number of aqueous solutions due to the introduction of the labeled material as³⁵SO ₄ ^2– . The solutions were of two components consisting of water and either sodium sulfate. The diffusion coeffcient measured for sodium chloride solutions is similar to literature data for the corresponding diffusion in sodium sulfate solutions. The results for sulfuric acid and ammonium hydrogen sulfate have been interpreted using literature data for the relative concentrations of the hydrogen sulfate and sulfate ions to obtain estimates for the diffusion coefficents of those ions. The results for perchloric acid, regarded as representing the diffusion coefficient of the hydrogen sulfate ion, have a much different concentration dependence to that observed for the estimates for that ion in sulfuric acid and ammonuim hydrogen sulfate. The difference is attributed to the effect of the perchlorate ion on the water structure.     

Solvent Modification in Ion-Pair Extraction: Effect on Sodium Nitrate Transport in Nitrobenzene Using a Crown Ether

A comparative quantitative analysis of the effect of solventmodifiers on the ion-pair extraction of an inorganic salt by a crown ether was conducted with the aim of advancing the understanding of transport of highly hydrophilic metal ions from aqueous salt solutions. Two classes of solvent modifiers that possess electron-pair donor (EPD) or hydrogen-bond donor (HBD) groups were investigated. The equilibrium constants corresponding to the extraction of sodium nitrate into nitrobenzene (NB) employing model neutral host cis-syn-cis-dicyclohexano-18-crown-6 (compound 1) with and without solvent modifier were determined using the SXLSQI computer model. For a series of EPD modifiers—including tri-n-butyl- and tri-phenylphosphate, tri-n-butyl- and tri-phenylphosphine oxide, N,N-di-n-butyl- and N,N-di-phenylacetamide—the enhancement of the NaNO₃ extraction by compound 1 was found to be dependent on the hydrogen-bond acceptance ability of the modifier as quantified by the β solvatochromic parameter. A HBD modifier 3,5-di-t-butylphenol (compound 8), which forms strong hydrogen bonds with nitrate anion in NB, exhibited even greater enhancement of the NaNO₃ extraction by compound 1. The determined extraction constants were correlated with the β- or α-solvatochromic parameters of the solvent modifiers and linear trends were observed. Hydrogen bond interaction between compound 8 and nitrate anion in the presence of the sodium-loaded crown ether in the extraction phaseswas studied by vibrational spectroscopy.     

Specific heats of aqueous solutions of NaCl,NaBr, and KCl: Comparisons with related thermal properties

Earlier unpublished measurements of the specific heat capacities of aqueous NaCl, KCl, and NaBr solutions from 5 to 85°C and from 0.05m to saturation are presented. A twin calorimeter was used. A precision of nearly 1 part in 10⁴ in the specific heat capacity is claimed. The results are compared with literature values (summaries or original data) for heat capacity, heat of dilution, and activity coefficient of these salts in solution by means of a polynomial in half-integer powers of molality and temperature. It is found that our values agree well with the more recent literature values of the heat capacities. Small systematic inconsistencies between the various types of data were found.The experimental results presented here are taken from the postdoctoral work of Dr. F. W. Lamb, 1946–47, and from the master's thesis of Dr. J. E. Tanner, Indiana University (1954), obtainable from University Microfilms, Inc., Ann Arbor, Michigan, order number M-763.     

Enzymatic determination of phosphatidylcholine in human erythrocyte membranes

An enzymatic method for direct colorimetric determination of phosphatidylcholine (lecithin) in solubilized red cell membrane samples has been developed. The method, based on the sequential action of phospholipase D (cabbage), choline oxidase, and peroxidase, is capable of determination of samples under 5 nmol and thus may be used on packed membrane samples as small as 4 μl.     

Thermodynamic quantities for the interaction of H+ and Na+ with C2H3O 2 − and Cl− in aqueous solution from 275 to 320°C

The aqueous reactions, {ie865-1}were studied as a function of ionic strength at 275, 300, and 320°C using a flow calorimetric technique. Log K, H and S values were determined from the fits of the calculated and experimental heats while Cp values were calculated from the variation of H values with temperature. The log K and H values for the first two reactions agree well with literature values at these temperatures. No previous results have been reported for the third reaction. The use of equations containing identical numbers of positive and identical numbers of negative charges on both sides of the equal sign (isocoulombic reaction principle) was applied to the log K values determined in this study. The resulting plots of log K for the isocoulombic reactions vs. I/T were approximately linear, which demonstrates that the Cp values for these reactions are approximately zero.Deceased 5 September 1987     

焙烤食品中糖精钠、富马酸二甲酯、苯甲酸和山梨酸的高效液相色谱法测定

研究了采用高效液相色谱同时测定焙烤食品中糖精钠、富马酸二甲酯、苯甲酸和山梨酸的检测方法；样品经氨化甲醇溶液提取后，用盐酸中和，水定容过滤后即可直接测定；检测波长220m，流动相采用甲醇与含0．03mol/L乙酸钠-0．03mol/L冰醋酸—0．008mol/L溴化四丁铵的水溶液混合液(体积比35：65)；4种组分的回收率在85％—109％之间，相对标准偏差小于6．2％(n=6)；该法简单、快速、准确，可用于饼干、月饼等焙烤食品中糖精钠、富马酸二甲酯、苯甲酸和山梨酸的日常检测。     

纳米管钛酸钠的组成分析

以NaOH与多晶粉末TiO2作用制备了纳米管.使用原子吸收分光光度法、紫外-可见吸收分光光度法和失重分析三种分析方法,确定了该纳米管材料的组成为Na2Ti2O4(OH)2.     

Electrochemical determination of electroinactive guests of b-cyclodextrin at a self-assembled monolayer interface

A novel determination method of electroinactive molecules by means of electrochemical technique is presented. A new self-assembled monolayer containing cyclodextrin(CD) is prepared with mono(6-o-p-tolylsulfonyl)-b-cyclodextrin. Although this derivatization process leads to a b-CD coverage of 10% of a full monolayer, this layer shows an effective host-guest response to ferrocene. The interfacial ferrocene complexation gives a response similar to that expected for a Langmuir adsorption isotherm yielding a stability constant of 4.2×104 mol-1@L and a maximum ferrocene coverage of 8.6′10-12 mol/cm2. The redox peak currents of the surface-confined ferrocene de-crease upon addition of competing b-CD guest species to the solution, such as m-toluic acid(mTA) and sodium dodecyl sulfonate(SDS). This principle has been used for the determination of the electroinactive molecules, mTA and SDS in the concentration ranges of 0.8-2.7 mmol/L and 5-100 nmol/L, respectively.