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1.
It was shown in previous papers, that many titrimetric problems can be solved by observing the pressure change of a closed system above the solution titrated at the equivalence point. This principle was made the basis of a gasometric titration method in which the end-point is found graphically. The titrant is added to the sample solution in measured increments at fixed intervals of time and the corresponding gas pressure or volume of the system is recorded and then plotted against the volume of added titrant. Half a dozen readings are sufficient to establish the end-point of a titration, which is found at the intersection of two straight lines. This graphical method was applied to cerimetry and chlorometry, as well as to some other analytical reactions (determination of nitrite, nitrate, hydroxide and carbonate) already described in previous papers on the gas pressure end-point technique. The results are comparable in precision and accuracy to the values obtained by the conventional visual end-point titrations. A gasometric titration takes about 10 minutes. The presence of other substances in the sample capable of reacting with the titrant does not necessarily cause interference. 相似文献
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An improved method of phase titration has been developed for the analysis of binary or pseudo-binary systems. A clarification end-point is used in place of the usual cloud end-point. Advantages are that end-points are equally sharp over a wide sample composition range, the titration volume is a very nearly linear function of composition so that often only one calibration point is needed, and the technique can be extended to cover the entire binary composition range. 相似文献
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Even ions which do not release gases with a certain titrant can be determined by direct gasometric titration. To achive this end, a substance which liberates a gas with the titrant, must be added to the sample solution. The end-point of the main reaction can be read from the gasometric titration curve of this indicator substance.This principle is applied in the present paper to the titration of ferrous and stannous ions by potassium dichromate. Hydrazine sulfate serves as indicator. The results are comparable in precision and accuracy to the values obtained by the conventional visual end-point titrations. 相似文献
4.
The systematic titration error which is introduced by the intersection of tangents to hyperbolic titration curves is discussed for precipitation reactions. A simple expression for the systematic titration error is derived, and S/Cx2 is proposed as a measure of the sharpness of the titration curve. The effects of the conditional solubility product (S), the concentration of the unknown component (Cx), and the ranges used for the construction of the end-point, are considered. A graphical method is presented for the selection of pairs of ranges which result in small systematic titration errors. For equal values of S/Cx2 and 1/KCx, the optimum combinations of ranges are different for precipitation and complexation titrations. The differences are not large for values smaller than about 0.002. For titration curves with a reversed L-shape, the error is calculated when the end-point is constructed by the intersection of the tangent to the second branch of the curve with volume axis; in this case equal ranges result in the same titration error for equal values of S/Cx2 and 1/KCx. The systematic titration error is equal to -S/Cx2 when the tangent to the curve is taken at fa = 3.0. 相似文献
5.
Monosegmented flow analysis (MSFA) has been used as a flow-batch system to produce a simple, robust, and mechanized titrator
that enables true titrations to be performed without the use of standards. This paper also introduces the use of coulometry
with monosegmented titration by proposing a versatile flow cell. Coulometric generation of the titrand is attractive for titrations
performed in monosegmented systems, because the reagent can be added without increasing the volume of sample injected. Also,
biamperomeric and potentiometric detection of titration end-points can increase the versatility of the monosegmented titrator.
The cell integrates coulometric generation of the titrand with detection of end-point by potentiometry or biamperometry. The
resulting titrator is a flow-batch system in which the liquid monosegment, constrained by the interfaces of the gaseous carrier
stream, plays the role of a sample of known volume to be titrated. The system has been used for determination of ascorbic
acid, by coulometric generation of I2 with biamperometric detection, and for determination of Fe(II), by coulometric generation of Ce(IV) with potentiometric detection
of the end-point, both in feed supplements. 相似文献
6.
A new type of automatic recording titrator has been developed. The titrant is added intermittently and the titration curve is recorded stepwise, potential changes being registered in the intervals between deliveries of titrant. The increments of titrant and the intervals can be pre-set, but give the best results if controlled automatically during the titration. The end-point and the volume of titrant consumed are read from the recorded titration curve. 相似文献
7.
A new numerical method of determining the position of the inflection point of a potentiometric titration curve is presented. It consists of describing the experimental data (emf, volume data-points) by means of a rational spline function. The co-ordinates of the titration end-point are determined by analysis of the first and second derivatives of the spline function formed. The method also allows analysis of distorted titration curves which cannot be interpreted by Gran's or other computational methods. 相似文献
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The triangle-programmed titration technique brings together the advantages of flow-through techniques and titration methods. Titrations with bromine prepared by current-programmed electrolysis are reported; suitable instrumentation is described for biamperometric end-point indication. The electrode processes and the effects of different parameters of the reagent addition program are discussed. The applicability of the method to organic and inorganic substances is described. The technique is applicable to flowing sample solutions of small volume, and the rate of analysis is similar to that achieved with other semi-automated analyzers. 相似文献
10.
Fractional mg quantities of ferric iron in 100 ml of solution can be titrated at PH 3.5 with a solution of ethylenediaminedi(o-hydroxyphenylacetic acid). The end-point is found photo- metrically. Errors are generally under 1%, and a number of metals do not interfere. By scaling down the volume of the solution and the titrant concentration, the titration can be extended to μg quantities of iron, and mg quantities are also accessible by changing to a wave length where the sensitivity is not so great. The titration may be useful in certain applications. 相似文献
11.
Tetraethylenepentamine is a very selective titrant for the determination of copper in acidic medium. With amperometric end-point detection as little as 0.1 mg copper in a volume of 25 ml can, be determined with an accuracy of ± 1%. When the titration is performed in acetic acid/ ammonium acetate buffer of pH 4.1, only mercury causes significant interference. 相似文献
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13.
Masadome T 《Talanta》2003,59(4):659-666
The reaction of the cationic dye, crystal violet (CV) with the anionic polyelectrolytes such as potassium poly (vinyl sulfate) (PVSK) results in a decrease of the absorbance of CV at the maximum absorption wavelength (590 nm). This change of the absorption spectra of the CV has been already applied to the determination of anionic polyelectrolytes using flow injection analysis method. In this paper, CV was applied to the indicator for the determination of cationic polyelectrolytes such as poly (diallyldimethylammonium chloride) (Cat-floc) by photometric titration, using a PVSK solution as a titrant. The end-point of the titration is detected as the break point of the titration curve. A linear relationship between the concentration of cationic polyelectrolyte and the end-point volume of the titrant exists in the concentration range from 0 to 5×10−5 eq. mol dm−3 for Cat-floc, glycol chitosan and methylglycol chitosan. The effects of the concentration of CV and coexisting electrolytes in the sample solution and the effect of pH of the sample solution on the degree of the change of absorbance at the end-point were also examined. 相似文献
14.
ZHAOGe LIUMeng LIUKuai-zhi QUJiang-ying CHENGGang DUZu-ling 《高等学校化学研究》2003,19(4):390-394
The feasibility of using electrodes modified with polyaniline incorporated carbon particles films for im-proving the precision of coulometric titration is demonstrated. The problem of large deviation produced dur-ing determining polyisoprene by coulometric titration with direct titration technique (double Pt electrodes indi-cating electrode) has been solved. In the titration process, polyisoprene alcohol, an electro-inactive species, is adsorbed on the surface of the bare Pt electrode, which inhibits the electrode reaction of Br- and Br2. Therefore, when the titration reaches the end-point, the detected current will slowly change with time, which can make the repeatability of end-point poor, The atomic force microscopic images show the morpholo-gy of the electrode surface of adsorbing polyisoprene alcohol. The application of the chemically modified elec-trode instead of the bare Pt electrode to indicating the end-point has been investigated. The results show that the Pt electrode coated with polyaniline incorporated carbon particles films is an excellent indicator electrode. This electrode has advantages that the indicating signals are sharp and repeatable at end-point. The precisionand the accuracy of the determination of polvisoprene alcohol are satisfactory. 相似文献
15.
《Analytical letters》2012,45(10):723-728
Abstract A new method for the end-point detection in complexometric titration using a tensammetric wave of organic reagents such as oxine and alizarin complexone (ALC) was studied. The tensammetric wave of these reagents disappears by their chelate formation and reappears by the liberation of free indicator during the exchange reaction between indicator chelate and EDTA. This mechanism is utilized for the end-point detection in complexometric titration of metals. Since the sensitivity of tensammetric wave is extremely high, very sharp end-point can be obtained for the titration of metals even in the concentration of 10?5M. 相似文献
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A plasticized poly (vinyl chloride) (PVC) membrane electrode sensitive to stearyltrimethylammonium (STA) ion is applied to the determination of cationic polyelectrolytes such as poly (diallyldimethylammonium chloride) (Cat-floc) by potentiometric titration, using a potassium poly (vinyl sulfate) (PVSK) solution as a titrant. The end-point of the titration is detected as the potential change of the plasticized PVC membrane electrode caused by decrease in the concentration of STA ion added to the sample solution as a marker ion due to the ion association reaction between the STA ion and PVSK. The effects of the concentration of STA ion, coexisting electrolytes in the sample solution and pH of the sample on the degree of the potential change at the end-point were examined. A linear relationship between the concentration of cationic polyelectrolyte and the end-point volume of the titrant exists in the concentration range from 2×10−5 to 4×10−4 N for Cat-floc, glycol chitosan, and methylglycol chitosan. 相似文献
19.
A method is described for the estimation of a systematic titration error which is introduced by linear extrapolation of hyperbolic titration curves in amperometric, photometric, and other instrumental titrations. It is assumed that the titration is based upon a single-step ion-association reaction mA + nB right harpoon over left harpoon A(m)B(n) and that the measured physical property falls within known minimum and maximum values. The procedure is suitable for end-point determination, even when the titration curves have extensive curvature, and for predicting the choice of optimum experimental conditions for a given titration. 相似文献
20.
The optimum conditions for the titration of antimony(III) with dichromate, and diphenyl-aminesulphonic acid as indicator, have been established. No iodine catalyst is used; the analytical reaction is based on an induced reaction with iron(II) as inductor. The titration can be done as easily as an iron(II) titration and the end-point is equally sharp. Titrations are possible with 0.01N solutions. 相似文献