High accuracy pre-formed gradient discontinuous flow titrimetry

A variant of Discontinuous Flow Analysis (DFA) titrimetry is described in which a pre-formed gradient is established between two titrant concentrations with the analyte aspirated at a constant rate into the gradient. The gradient encompasses a narrow range of analyte concentration (10% variation in this instance), and provides a high encoder pulse resolution. A simple acid-base titration model using photometric endpoint detection achieved comparable accuracy to conventional batch titrimetry (approximately 0.1% relative), with excellent calibration linearity (r(2) = 0.9997, standard error of estimation approximately 0.05% relative over six standards). Titrations were performed at the rate of one every 25 sec; with 0.8 ml of analyte and 0.85 ml of titrants consumed. The method is fully automatic.     

High precision titrimetry: An examination of the attainable precision

A re-examination and critical assessment of the mechanical precision of titrimetric processes, with particular reference to the drainage errors of burettes, has been made and some manipulative improvements suggested.The piputte-dilution method offers a useful improvement in the precision of volumetric methods, further increase in mechnical precision affords little or no improvement in accuracy of determination.     

High precision titrimetry: A System of weight titrimetric analysis using arbitrary standards

A technique of arbitrary standard weight titrimetric analysis has been proposed for realising the ultimate degree of mechanical precision of which titrimetric processes are capable, and has been applied to reactions and methods of end-point location which are particularly favourable. A form of needle-valve weight burette is also described. It has been found that, even in the most favourable cases and working under the conditions of atomic weight determination, there is a limit to the precision and therefore accuracy of the analytical results, which is set by physico-chemical considerations, and which is at least one order less than the maximum attainable mechanical precision of measurement.     

沉淀单点滴定法与双点滴定法研究

导出了沉淀单点滴定法与双点滴定法计算式。以银电极为指示电极 ,Ag 标准溶液为滴定剂 ,对Cl-、Br-、I-及SCN-等离子的测定进行了研究 ;对影响测定结果准确度的因素进行了讨论。实验发现 ,在α =1 .0～ 1 .1的条件下 ,单点滴定法有较高的准确度 ;在α1 ≈ 1 .0～ 1 .1、ΔV =0 .5～ 1 .0mL的条件下 ,双点滴定法有较高的准确度     

Determination of potassium by titrimetry

Epp's method is modified by the addition of solid calcium hydroxide to the sample solution. This simplified the procedure, increased the rapidity and lessened the sources of error. With samples containing various ions except ammonium ion, potassium (conc. of KCl 0.25 to 1.8 x 10(-2)M) was determined within 0.4% of error, by means of corrections for the existence of a large quantity of sodium chloride and for the solubility of potassium tetraphenylborate.     

End-point sharpness in thermometric titrimetry

It is shown that the sharpness of an end-point in a thermometric titration where the simple reaction A + B right harpoon over left harpoon AB takes place, depends on Kc(A') where K is the equilibrium constant for the reaction, and c(A') is the total concentration of the titrand (A) in the reaction mixture. The end-point is sharp if, (i) the enthalpy change in the reaction is not negligible, and (ii) Kc(A') > 10(3). This shows that it should, for example, be possible to titrate 0.1 M acid, pK(A) = 10, using a thennometric end-point. Some aspects of thermometric titrimetry when Kc(A') < 10(3) are also considered.     

Stripping voltammetric detection in high-precision titrimetry

Anodic stripping voltammetry is used to detect the equivalence point in compleximetric titration. The sensitivity of detection thus provided enables the attainable precision to be markedly improved. Theoretical treatment of the electrochemical deposition of a metal from media containing a complexing agent such as EDTA in large excess is based on the model of reversible reduction of the complex formed, as worst case. It is shown that anodic stripping voltammetry can be applied if the conditional stability constant of the complex is appropriate. Semi-automatic techniques are outlined for improving the speed and ease of operation. Indium, cadmium, and bismuth can be titrated with EDTA, with a relative standard deviation of less than 0.01%.     

Indirect determination of nitroglycerine by biamperometric titrimetry

A procedure is described for the determination of nitroglycerine in propellant samples by biamperometric titrimetry. The method is simple, avoids the use of expensive instruments, and is free from interferences other than those occurring in the classical techniques. The accuracy and precision are equal to those of existing methods. The reduction and titration steps are performed in the specially designed flask.     

Determination of insoluble azides by thermometric titrimetry

A method for determination of azide, based on the thermometric titration of this anion with hydrochloric acid, is described. Although this reaction has a large enthalpy change (DeltaH = -3.6 kcal/ mole), sulphate is added as an endothermic thermometric indicator to improve the end-point. The application of the method to the analysis of insoluble azides has been studied.     

Simple instrument for titrimetry without indicators gas pressure end-point technique: Iodometry,iodimetry, iodate and periodate titrimetry

The present paper shows, that the gas pressure end-point technique can be applied to several oxidation reduction titrations. lodometry, iodimetry, iodate and periodate titrimetry were studied. Standard arsenite, iodine and hydrazine sulfate solutions òwere used as titrants. The results are comparable in precision and accuracy to values obtained by the standard visual end-point titrations.     

Estimation of errors in differential thermometric titrimetry

Equations are derived predicting the error for applications of thermistors as temperature sensors in differential thermometric titrimetry. The predictions are compared with the error measured experimentally for a circuit with NTC thermistors.     

沉淀双点滴定法测定盐酸左旋咪唑

以Ag^＋作滴定剂,分别用双点滴定法和传统电位滴定法对盐酸左旋咪唑片进行了测定。试液的配制采用了过滤和不过滤两种方法。测定结果表明：所有方法测得的结果均在《药典》允许的范围之内;本法测定结果与《药典》规定方法的对照偏差约为2%-3%;采用过滤和不过滤两种方法配制试液的测定结果之间的偏差约为1%。     

The palladium electrode in aqueous and nonaqueous titrimetry

Two modifications of the palladium-hydrogen electrode of Schwing and Rogers have been made and tested. A new form of “generation” electrode with a vertical palladium diaphragm and fast constant speed circulation has been devised. This form of electrode responds rapidly and has been used in a variety of acid-base titrations in aqueous and nonaqueous systems.     

Effectivity of solvents-A new approach in non-aqueous acid-base titrimetry

A new approach for selection of a suitable solvent system as a medium for non-aqueous acid—base titration is proposed. The essence of the approach is the development of a new criterion called “effectivity”. The latter is based on consequences of the Brønsted and Izmailov acid—base theories and represents a quantitative measure for improving or worsening the titration conditions of acids and bases in non-aqueous solvents as compared with water. The “effectivity” E is given by the relation E = ΔpK_s - ΔpK_s where ΔpK_s is the difference between the logarithmic values of the autoprotolysis constants of water and the solvent in question, and ΔpK is the so-called medium effect. The latter is a constant value which shows that acids and bases with the same charge alter their strength to the same extent when transferred from water into a non-aqueous solvent. The medium effect is calculated by statistical treatment of a great number of acid—base constants determined experimentally both in water and the non-aqueous solvent in question. The effectivity of the solvents most often used in non-aqueous acid—base titrimetry, determined by this approach, shows that in many cases these solvents offer significant advantages over water, but drawbacks are also observed. Some limitations of the approach are discussed. Special attention is paid to dimethylsulphoxide and its mixtures with water, which prove to be highly effective media for the acid—base titration of many substances.     

High frequency excitations in a molecular glass

Neutron inelastic triple-axis spectra of CD₃OD/6%D₂O in the glassy and liquid phases are reported. Both the dispersion and damping of the sound modes show characteristic features as the temperature is lowered to the glassy regime. Furthermore, analysis of the observed scattering intensities reveals the presence in the glass of a second component centred at zero frequency which is not observed in the liquid.     

High frequency faradaic rectification voltammetry at microelectrodes

An experimental setup for carrying out faradaic rectification measurements at micrometer-sized electrodes under potential control is described. A new method of data analysis is proposed that allows the determination of the standard rate constant and the electron-transfer coefficient of a fast charge transfer process without knowing the impedance of the microelectrode. This method is based on the frequency dependence of the shape of the faradaic rectification voltammograms (i.e., the average width of the peaks and the ratio of the peak heights) rather than on the magnitude of the faradaic rectification signal. The method was tested in the determination of heterogeneous electron transfer kinetics of Fe(CN)6(3-/4-) and Ru(NH3)6(2+/3+) in aqueous solutions on a platinum microelectrode (12.5 microm in radius) and ferrocene/ferrocinum redox couple in a dimethylformamide solution on a gold microelectrode (12.5 microm in radius).