PURE SUBSTANCES, FUSED SALTS, SOLID ELECTROLYTES 353 



perhaps to be classed as salts. In other words, these compounds should 

 be classed, not with the ordinary hydrocarbons, but rather with the dis- 

 tinctly salt-like substances. These derivatives, when dissolved in water, 

 or other suitable solvents, yield solutions which conduct the current with 

 great facility and which often form compounds with the solvent. Hydro- 

 chloric acid forms a stable complex, ammonium chloride, with ammonia; 

 and with water at low temperature it has been shown to form a complex 

 HC1.H 2 0. 3 In water itself, therefore, hydrogen and hydroxyl ions do 

 not consist merely of a hydrogen atom and an OH group associated with 

 the positive and negative charge respectively, but rather of complexes in 

 which the solvent itself is involved. In a sense, therefore, water and 

 ammonia and hydrogen chloride may be considered to be related to salts. 

 However, the typical salts in a fused state exhibit in most instances a 

 conductance much greater than that of the substances which we have 

 just been discussing. 



With a few exceptions, fused salts conduct the current with extreme 

 facility. Among these exceptions mercuric chloride is one of the most 

 common and striking examples. This salt is itself an electrolytic solvent 

 for other salts, while its specific conductance in the pure state is very 

 low.* Correspondingly, solutions of mercuric chloride in other solvents, 

 as for example water, appear to be only slightly ionized. This class in- 

 cludes the organic tin salts of the type R 3 SnX. Trimethyltin iodide, for 

 example, is a liquid at ordinary temperatures whose conductance is less 

 than 4 X 10~ 5 . This salt when dissolved in water is ionized nor- 

 mally. 5 



2. Fused Salts. Inorganic substances which are non-electrolytes in 

 solution, in general, possess only a very low conducting power in the pure 

 state. This, for example, is the case with boric oxide. On the other 

 hand, oxides of the strongly electropositive elements appear to be con- 

 ductors in the fused or even in the solid state. It is, however, the typical 

 salts in their fused state which are of greatest interest. These substances, 

 in general, conduct the current with extreme facility, by means of a 

 purely ionic process, since, as has been shown, Faraday's law applies. 



In Table CXXXV are given values of the specific conductance \i of 

 sodium nitrate at different temperatures, together with the equivalent 

 conductance A as calculated from the known specific volume, the fluidity 



of the fused salt F, and the ratio of the conductance to the fluidity ^ . 6 



JT 



'Rupert, J. Am. Chem. Soc. SI, 851 (1909). 



Foote and Martin, Am. Chem. J. 41, 45 (1909). 



8 Unpublished observations by Mr. C. C. Callis in the Author's Laboratory: 



Goodwin and Mailey, Phys. Rev. 25, 469 (1907) ; t&id., 26, 28 (1908). 



