Electrical conductivity measurement apparatus

Methods of Measurement. The positive and negative small-ion concentrations, the electrical conductivity, and ion mobilities were measured with a Gerdien-type instrument. From analyses of current-versus-voltage curves obtained with the apparatus operated at constant volume flow, values for the ion density, the conductivity, and the mean mobility of the ions can be determined (Wilkening and Romero, 1981). 

Methods. The differential heats of adsorption of reagents and the differential heat of their interaction on the nickel oxide surface were measured in a Calvet microcalorimeter with a precision of 2 kcal. per mole. The apparatus has been described (18). For each adsorption of a single gas, small doses of gas are allowed to interact with a fresh nickel oxide sample (100 to 200 mg.) placed in the calorimeter cell maintained at 30°C. At the end of the adsorption of the last dose, the equilibrium pressure is, in all cases, 2 torr. Duplication of any adsorption experiment on a new sample gives the same results within 2 kcal. per mole of heat evolved and 0.02 cc. of gas adsorbed per gram. Electrical conductivities of the nickel oxide sample are measured in an electrical conductivity cell with platinum electrodes (1) by a d.c. bridge. 

The electrical conductivity (or resistivity) of an aqueous pigment extract is determined from the electrical conductance (or resistance). For standards, see Table 1 ( Resistivity ). Apparatus centrifuge with glass containers, resistance measurement bridge, electrolytic cell. 

Knoche and Wiese (1976) described a p-jump apparatus using an optical absorption detection system, but relaxation times <3 x 10 4s could not be observed and the detection was not as sensitive as when electrical conductivity was measured. A p-jump apparatus based on Strehlow s design (Strehlow and Becker, 1959) but using spectrophotometric detection was also described by Goldsack et al. (1969). 

Gu, W.Y. and Justiz, M.A. (2002) Apparatus for measuring the swelling dependent electrical conductivity of charged hydrated soft tissues. J Biomech Engng 124, 790-793... 

Fig. 6. Schematic of the apparatus for the measurement of growth kinetics in constant composition solution conditions. Both the C02 concentration and electrical conductivity are kept constant by the addition of a gas mixture and titrant solution.

Local axial and radial gas-phase characteristic measurements were made at steady-state conditions in a 0.108-m-i.d. slurry bubble column apparatus with a two-point electrical conductivity probe. 

IE. Electrical Methods of Analysis. Among the various electrical properties which have been used for analysis and for which measuring apparatus may be directly incorporated in the reaction chamber are the dielectric constant the electrical conductance the pH by using glass, calomel, or H electrodes the redox potential and, in the case of gas reactions, the thermal conductivity. These properties are easily measured and lend themselves, as do the optical methods, to automatic recording devices. However, they also must be used only after careful calibratiomand do not give better than 1 per cent accuracy without unusual attention. 

The use of stop-flow techniques to observe the formation of carbenium ions in actual polymerising systems was introduced by Pepper et al. about ten years ago and is presently exploited by various research groups with increasingly fast equipment. These experiments consist essentially in mixing monomer and catalyst solutions in an appropriate flowing system coupled vrith a rapid detection apparatus which takes absorption spectra and can measure other physical parameters, such as the electrical conductivity of the reaction mixture. This technique is certainly the most appropriate for studying the rise and fate of ionic active species in cationic polymerisation and the few, but remarkable, results obtained so far will be reviewed in the various sections dealing vrith specific systems. 

The electrical conductivities of soln. of potassium chloride have been determined with a great degree of precision since aq. soln. of this salt are commonly used as normal standard liquids for measuring the resistance-constants of the apparatus employed in conductivity determinations. According to C. Deguisne, the coefE, K at in reciprocal ohms is represented by the expression 18)+6( —18) ],... 

An example of how kinetic measurements may suggest a mechanism for complex formation between soil compounds is the research of Lopez-Quintela et al. (1984) who studied the reaction between Al ions and citric acid and leaf extract in aqueous solutions. A stopped-flow apparatus was used to study the kinetics and the reaction progress was monitored by electrical conductivity. 

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