Electronic and Electrolytic Conductors

All substances can be divided from the point of view of their capability to conduct the electric current into conductors and non-conductors (insulators or dielectrics). The difference between these two groups is not always conspicuous as some substances can be denoted as poor conductors as well as imperfect insulators. 

On the passage of electric current through the conductor the electricity moves from points with higher negative potential to points with lower negative potential. We must take into consideration the mechanism of this motion, which is not identical for all conductors but depends on their nature. So we have two classes of conductors, the electronic and the electrolytic conductors. 

Electronic conductance is characteristic for the so called conductors of the first class, i. e. for metals (both in solid and fused state) and some metal oxydes, carbides, sulphides, phosphides and borides and it can be explained by assuming the existence of free electrons which act in solid matter as anions. Under the influence of the external electric field these easily movable electrons start an ordered motion while the atoms deprived of their electrons, which are in fact cations, take practically no part in the current conduction and, apart from their vibration within the mean equilibrium positions, remain practically immobile. The passage of the current does not manifest itself by a chemical change of the 

Electrolytic conductance, a property of the so called conductors of the second class, is encountered mainly in the case of salts in dissolved, melted and solid state. Among these compounds are sulphates, halides, nitrates, silicates, also many oxides, hydroxides, sulphides and so on. The same group includes also the potential electrolytes, i. e. the substances from which ions are formed only in mutual reaction with a solvent (solutions of acids in basic solvents, solution of bases in acid solvents, further amines and different chlorine derivatives of organic compounds in liquid sulphur dioxide, nitro-compounds in liquid amines etc.). Finally also numerous colloidal solutions (such as proteins and soaps) conduct the current like electrolytes. 

Unlike the electronic conductors the transfer of electricity is not mediated 

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The distinction between electronic and electrolytic conductors is not sharp, for many substances behave as mixed conductors that is, they conduct partly electronically and partly electrolytically. Solutions of the alkali and alkaline earth metals in liquid ammonia are apparently mixed conductors, and so also is the jS-form of silver sulfide. Fused cuprous sulfide conducts electronically, but a mixture with sodium or ferrous sulfide also exhibits electrolytic conduction a mixture with nickel... 

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