Liquid electrical conductivity

When detecting the interface between two liquids, electrical conductivity, thermal conductivity, opacity, or sonic transmittance of the liquids can be used. Interface-level switches are usually of the sonic, optical, capacitance, displacer, conductivity, thermal, microwave, or radiation types. Differential pressure transmitters can continuously detect the interface, but, if their density differential is small relative to the span, the error will be high. On clean services, float- and displacer-type sensors can also be used as interface-level detectors. In specialized cases, such as the continuous detection of the interface between the ash and coal layers in fluidized bed combustion chambers, the best choice is to use the nuclear radiation sensors. 

Transfer of an electric current through a solid or liquid (electrical conduction). In metallic or electronic conductors the current is carried by a flow of electrons, the atomic nuclei remaining stationary. This type of conduction is common to all metals and alloys, carbon and graphite, and certain solid com-... 

Hamilton D C, Mitchell A C and Nellis W J 1986 Electrical conductivity measurements in shock compressed liquid nitrogen Shock M/aves in Condensed Matter (Proc. 4th Am. Phys. Soc. Top. Conf.) p 473... 

Liquid ammonia (p. 216). like water, is very slightly dissociated, and shows a very small electrical conductance ... 

Table 8.34 Electrical Conductivity of Various Pure Liquids 8.161...

However, conductive elastomers have only ca <10 of the conductivity of soHd metals. Also, the contact resistance of elastomers changes with time when they are compressed. Therefore, elastomers are not used where significant currents must be carried or when low or stable resistance is required. Typical apphcations, which require a high density of contacts and easy disassembly for servicing, include connection between Hquid crystal display panels (see Liquid crystals) and between printed circuit boards in watches. Another type of elastomeric contact has a nonconducting silicone mbber core around which is wrapped metalized contacts that are separated from each other by insulating areas (25). A newer material has closely spaced strings of small spherical metal particles in contact, or fine soHd wires, which are oriented in the elastomer so that electrical conduction occurs only in the Z direction (26). 

FIG. 22-44 E mpirical relationship between 2), the volumetric fraction of hq-iiid in common polydisperse foam, and K, the electrical conductivity of the foam divided hy the electrical conductivity of the liquid. [Chang and Lemhch, J. Colloid Interface Sci., 73, 224 (1980).]... 

Kc = relative dielectric constant of the liquid, dimensionless C = electrical conductivity of the hquid, pS/m... 

PCBs and PCTs are particularly troublesome liquids because of their toxicity and persistence in the environment. They are defined as polychlorinated biphenyls, polychlorinated terphenyls, monomethyl-dibromo-diphenyl metliane, monomethyl-dichloro-diphenyl metliane or monomethyl-tetrachlorodiphenyl methane. With low electrical conductivity and heat resistance they found wide use as dielectric fluids and were formerly used as hydraulic fluids. PCBs have not been made in the UK since 1977 and whilst most new uses for the substance are banned in most countries, around two-thirds of the 1.5 million tonnes manufactured in Europe and the US prior to 1985 still remain in equipment such as transformers. PCTs have been used in the past in a restricted range of specialist industrial applications. 

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