摘要:

A detailed description of the construction of an improved dual-channel integrating ultramicro flame photometer for simultaneous analysis of potassium and sodium is presented.

ISSN:1073-9149    

DOI:10.1080/10739146808543244

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The construction of an inexpensive but accurate and versatile solution calorimeter is described. Solid, liquid, and gaseous samples can be used in combination with almost any solvent system desired. A wide range of heats can be measured with 1-2% precision and accuracy. The methods of sample measurement and introduction are discussed.

ISSN:1073-9149    

DOI:10.1080/10739146808543245

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Development of a rapid automatic method for recording differential capacity curves as a function of potential is discussed. Various electrolytes, electrolyte concentrations, reference electrodes, and frequencies were investigated. The behavior of Teflon as a capillary material for the hanging drop electrode is compared to that of glass and siliconized glass. Moderately good agreement with impedance bridge data is noted. The principal discrepancies between results obtained by the automatic and bridge methods are quantitatively attributed to the area variation. Improvement is found for a platinum-supported drop electrode for which this dependence of area on surface tension is absent. Good agreement with impedance bridge data and electrocapillary data is observed for such electrodes, and the small discrepancies which still remain are consistent with effects, previously observed with hanging drop electrodes, due to the presence of trace amounts of impurities.

ISSN:1073-9149    

DOI:10.1080/10739146808543246

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The use of the second derivatives of the polarographic waves for analytical work in fast-sweep polarography has been investigated. Three-electrode potentiostatic control circuitry and controlled-drop-time dropping mercury electrode apparatus was used. With active, operational amplifier derivative and filter circuitry, the theoretically greater resolution of overlapping waves and freedom from base-line effects can be realized. A circuit has been designed which makes possible the high-precision readout of polarographic peak heights on a digital voltmeter. With the digital readout system and second derivative waves, a short-term reproducibility of the measurements approaching 0.1% can be achieved for concentrations above 10−4M. Above about 10&−5M, analyses can be performed with 1% accuracy, using only a single polarographic cell with blank corrections or by peak-to-peak measurement of the second derivative wave. Below 10−5M it is advantageous to use a combination of second derivative and two-cell differential operation.

ISSN:1073-9149    

DOI:10.1080/10739146808543247

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The circuits, theory, and performance characteristics are described of a controlled-potential dc polarograph (ORNL Model Q-1988-FES) which is designed to take advantage of the inherent high sensitivity and resolution of derivative dc polarography. Several circuit modifications for specific applications are described. Cell and electrode design considerations are given. The advantages of potentiostatic electrolysis in polarography, the advantages of the use of current-averaging and analog derivative circuits in improving the measurement and the interpretation of recorded dc polarograms, the attainment of ultimate high resolution through the recording of first derivative dc polarograms of good waveform, the achievement of high sensitivity by means of rapid derivative dc polarography, the practical advantages of first derivative over regular dc polarography, the relative advantages of first and second derivative dc polarography, and the practical advantages of rapid dc polarography are discussed. Conclusions are illustrated and substantiated by data.

ISSN:1073-9149    

DOI:10.1080/10739146808543248

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

During the course of kinetic studies in this laboratory, various designs of continuous-flow reactors have been advanced [1] in order to use the significant simplification of the rate equations, as derived by Harris [2], for a kinetic process. This communication reports the performance of a new assembly, recently designed in our laboratory, which combines on-stream sampling and modern chromatographic techniques with the principles of stirred flow, to attain the Harris conditions for the measurement of reaction rates.

ISSN:1073-9149    

DOI:10.1080/10739146808543249

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Both electrical and electrochemical tests are required to define, describe, and specify the performance of a polarograph when a polarograph or a cell or an electrode is newly constructed or placed in service, when work is to be started that is of special importance, or when poor results are obtained with a combination that has been in use. In the last case, the first question is whether the malfunction originates in the polarograph itself or in the cell-electrode assembly or is due to electrochemical problems specific to the sample just introduced. The polarograph is tested by means of electrical tests. If it is performing according to specifications, the overall system (and thus the cell and electrodes) is checked out by means of obtaining polarograms with reactions of well-known characteristics. Satisfactory electrical and electrochemical test methods which have evolved at Oak Ridge National Laboratory (ORNL) are set forth in this paper. For any specific polarograph, each of these tests is generally applicable, provided, of course, that the polarograph includes the feature or mode of operation for which the test is designed. Also, diagnostic criteria are given for establishing the degree to which the forms of recorded regular, first derivative, and second derivative dc polarograms (for simple, polarographically reversible test reactions) are adversely affected by circuit performance.

ISSN:1073-9149    

DOI:10.1080/10739146808543250

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor