334 Conductivity of Aqueous Solutions. Part XII. 



o 



For the measurements at 18 and 100 and in some of those at 128 

 and 156 the bomb was immersed in a liquid xylene or pseudocumene 

 bath, but at the higher temperatures it was heated in the apparatus shown 

 in fig. 2, page 12, in the vapors of boiling liquids (brombenzene at 156, 

 naphthalene at 218, isoamvlbenzoate at 260, bromnaphthalene at 281, 

 and benzophenone at 306). In the later experiments the heater and 

 the electrical connections were so arranged that the bomb could be 

 rotated (see fig. 14, page 64), thus causing thorough stirring of the 

 contents. 



By means of this apparatus conductance measurements have been made 

 up to 306 at all or nearly all the temperatures just mentioned with sodium 

 chloride, potassium chloride, silver nitrate, potassium sulphate, barium 

 nitrate, hydrochloric acid, nitric acid, sulphuric acid, acetic acid, ammo- 

 nium hydroxide, ammonium chloride, sodium acetate, and ammonium 

 acetate; at the temperatures up to 218 with magnesium sulphate, and 

 sodium hydroxide ; and from 18 to 156 at intervals of 25 or 28 with 

 nitric acid, phosphoric acid, sulphuric acid, potassium hydrogen sulphate, 

 and barium hydroxide. With most of these substances the measurements 

 have been made at four or more different concentrations varying between 

 0.1 and 0.002 normal. 



The final values of the equivalent conductance of these substances will 

 be found in the tables of the preceding parts on the following pages : 



Potassium and sodium chlorides 47 



Silver nitrate, barium nitrate, potassium sulphate, 



magnesium sulphate 103 



Acetic acid and sodium acetate 137-8, 225 



Ammonium hydroxide and ammonium chloride.. 174,225 



Hydrochloric acid 137, 262 



Sodium hydroxide . 174 



Nitric acid, phosphoric acid, sulphuric acid, potas- 

 sium hydrogen sulphate, and barium hydroxide 262 



These conductivity results have interest from a theoretical standpoint 

 mainly in two respects first, with reference to the equivalent conduct- 

 ance of the ions or their specific migration-velocities; and second, with 

 reference to the degree of ionization of the various substances. 



The values at the different temperatures of the equivalent conductance 

 (A ) extrapolated for zero concentration or complete ionization were 



11 

 obtained with the help of a function of the form = - K 1 (CA) n ~ 1 , 



A A 



which corresponds to the equation C(A A) = K(CA) n , by plotting 



1/A against (CA) M_1 , varying the value of n till a linear plot was 



obtained, and then extrapolating for zero concentrations.* All the 



so-derived values of A for the largely ionized electrolytes are summarized 



in the following table. The substances are arranged primarily according 



*A discussion of this method of deriving the A -value will be found in section 17 

 (Part II, page 50). 



