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[en] Highlights: • Comprehensive description of an experimental apparatus for coulometric titrations. • In-detail discussion of difficulties and challenges. • Validation of the system by measurements conducted in the Li-Sn system. - Abstract: The thermodynamic description of Li containing systems is readily accessible by coulometric titrations in combination with EMF measurements. Although this method is often encountered in literature, the experimental apparatus needed is in general only poorly described. As Li and its alloys are very reactive substances, many parameters like the materials used for the electrochemical cell, cell geometry, establishment of O2- and H2O-free atmosphere, etc. are all important factors for a successful measuring device. Therefore, an instrumental setup for coulometric titrations combined with EMF measurements is presented in detail, covering the general and the electronic setup used, as well as the structure of the electrochemical cell. The apparatus is validated with two measurements conducted in the Li-Sn system, which are further compared with literature data.
[en] The present method describes the determination of uranium(IV) using the extractospectrophotometric technique, and that of hydrazine utilizing the potentiometric titration method. Both uranium(IV) and hydrazine are estimated from the same sample. Interference studies of several anions and cations were also carried out. The relative standard deviation for uranium(IV) at 5.4 mg level was found to be 1.03% and that for hydrazine at 3.69 mg level was calculated to be 1.43%. (orig.)
[en] Null measurements formed a considerable fraction of the scientific work of Howard Malmstadt. He worked extensively to automate and perfect titration methods and he applied the titration process to potentiometric and spectrometric methods in a technique he called isomation. Further, a great deal of his work in automation took advantage of devices based on null principles. Null measurement and control systems directly compare the measured quantity with that of a standard which is then adjusted until the difference between the standard and measured quantities is zero. The output number (with units) is obtained from the setting of the standard. Direct measurement systems use conversion devices to convert the information from the measured quantity to a related number. Direct measurements require calibration to obtain the conversion factor and units while null measurements are calibrated inherently. Most modern measurement systems employ null devices, but as conversion devices in direct measurement systems rather than as part of a 'full' null system. There are advantages to be gained through a reconsideration of complete null measurement approach advanced so effectively by Howard Malmstadt
[en] Kinetics and mechanism of influence of aqueous extract from the wastes of tobacco production on electrochemical reactions in salt and acid mediums by potentiometric method has been studied. Based on polarization curves obtained the quantitative calculations on determination of metal dissolution rate have been done.
[en] Production of N and O atoms has been investigated by NO titration in flowing reactors for research study (5 litre) and for industrial applications (900 litre). The two reactors differ by the chamber volumes and compositions: pyrex glass for the small and steel for the big one. In the same conditions of pressure, power density and post-discharge time, it is measured about the same values of N-atom density inside the two reactors but the O-atom density is nearly one order of magnitude lower in the industrial one. Such a difference is explained from variations of destruction probability of N and O atoms on the reactor walls and by consideration of scaling up parameters. Such flowing reactors are applied to metal surface cleaning, polymer activation by O atoms and to sterilization processes by a synergetic effect of O atoms and UV emission of NOβ bands
[en] Different signal generation techniques were investigated for the development of a biosensor for Listeria monocytogenes. Conventional amperometry at an antibody-containing polypyrrole film electrode was found to be unsuccessful in detecting levels below 106 cells ml-1. More successful was the coupling of a covalently modified film with the use of electron mediators in a single device. This sensor was capable of reproducibly detecting Listeria at levels of 105 cells ml-1 in 30 min
[en] The revised potentiometric surface map here, using mainly 1993 average water levels, updates earlier maps of this area. Water levels are contoured with 20-m intervals, with additional 0.5-m contours in the small-gradient area SE of Yucca Mountain. Water levels range from 728 m above sea level SE of Yucca to 1,034 m above sea level north of Yucca. Potentiometric levels in the deeper parts of the volcanic rock aquifer range from 730 to 785 m above sea level. The potentiometric surface can be divided into 3 regions: A small gradient area E and SE of Yucca, a moderate-gradient area on the west side of Yucca, and a large-gradient area to the N-NE of Yucca. Water levels from wells at Yucca were examined for yearly trends (1986-93) using linear least-squares regression. Of the 22 wells, three had significant positive trends. The trend in well UE-25 WT-3 may be influenced by monitoring equipment problems. Tends in USW WT-7 and USW WTS-10 are similar; both are located near a fault west of Yucca; however another well near that fault exhibited no significant trend
[en] Highlights: • The principal condition for optimal titration experiment design is found. • The concentration range should be inversely proportional to the aggregation constant. • Restrictions to selection of experimental method are formulated. The principal condition for optimal experiment design, required for getting reasonable error for equilibrium aggregation constant, K, determination is obtained. This condition states that the selected concentration range for performing titration experiment should be inversely proportional to the expected value of K. As a consequence, the choice of physico-chemical methods for determination of aggregation parameters must obey this condition.
[en] Detection of the end point in potentiometric titrations has wide application on experiments that demand very low measurement uncertainties mainly for certifying reference materials. Simulations of experimental coulometric titration data and consequential error analysis of the end-point values were conducted using a programming code. These simulations revealed that the Levenberg-Marquardt method is in general more accurate than the traditional second derivative technique used currently as end-point detection for potentiometric titrations. Performance of the methods will be compared and presented in this paper