CONDUCTIVITY OF SODIUM HYDROXIDE IN AQUEOUS SOLUTION. 



molecules, having the simple formula H 2 O, that these, like the ice molecules, have a 

 larger molecular volume than the water molecules, and are destroyed by adding soda 

 to the solution. The addition of soda may then be regarded as simplifying the 

 solution mainly by lessening the proportion of associated and dissociated water 

 molecules, the water molecules themselves being converted into hydrates of soda 

 having somewhat similar properties to dihydml, but an even smaller molecular 

 volume. This view, which is an extension of the theories of RONTGEN and of 

 SUTHERLAND, appears to be fully justified by the experimental facts, and indeed it is 

 difficult to avoid the conclusion that in the neighbourhood of the boiling-point the 

 simple steam molecules form, if not the largest, at least a very important proportion 

 of the total number. 



TABLE XI. Solution Volume of 1 gramme of Sodium Hydroxide between C. and 



100 C.* 



PAKT V. THE CONDUCTIVITY OF SODIUM HYDROXIDE IN AQUEOUS SOLUTION 



AT 18 C. 



The only measurements that we have been able to find of the electrical conductivity 

 of sodium hydroxide in aqueous solution, apart from a single measurement by LOOMIS 

 ('Ann. Phys. Chem.,' 1897, vol. 60, p. 550) of the specific conductivity and density 

 of a normal solution, are those ot KOHLRAUSCH (' Wied. Ann.,' 1897, vol. 6, pp. 1 

 and 145 ; 1885, vol. 26, p. 161). As, however, the values given by KOHLRAUSCH 

 for the densities are considerably higher than those which we have deduced in 

 Part II. of this paper, it would seem that the accuracy of the electrical measure- 

 ments was very largely neutralised by the presence of neutral impurities in the 



* Our thanks are due to Mr. R. L. QUKRTIER for his help in calculating Tables IX. and XI. 

 [December, 1904. The first four rows of figures have been amended.] 



2 o 2 



