ON ELECTROLYTIC CONDUCTIVITY IN CONCENTRATED SOLUTIONS. 257 



For nitric acid there are only four points given between 1 and 5*9 normal, but for 

 these the greatest difference between the calculated and observed values is only + 1*1 

 per cent. At higher concentration the graph ceases to be even approximately 

 linear. 



The data for sulphuric acid are more complete. Six points, from 3- 8 normal, show 

 differences which do not exceed 0'5 per cent. As there is no indication of a trend in 

 these differences, it is clear that equation (1) is applicable within this range. As in the 

 case of nitric acid the graph ceases to be even approximately rectilinear at higher 

 concentration. The data given are calculated for ^H 2 S0 4 . Obviously they might 

 have been calculated for H(HS0 4 ). The advantages of this latter mode of representing 

 the facts will be discussed in connection with the new data relating to the halogen 

 acids. 



The Constants of Equation (1). 



Tables B and C show the manner in which anions and cations are grouped together 

 according to the value of the constants a and b. 



Certain groupings are clearly marked. The constants a for the chlorides, bromides, 

 and iodides of potassium and ammonium agree closely. The isomorphous sulphates of 

 Mg, Mn, Zn, Cd, Cu, and Fe show values for a and b which lie within narrow limits, viz., 

 30 to 34 for a, and 5*0 to 5 '9 for b. In the case of the chlorides of Mg, Ca, Sr, and 

 Ba the values for a rise in order from 75 for Mg to 83 for Ba, while conversely the values 

 for b fall from -10 for Mg to -7 "31 for Ba. These tables show clearly how much remains 

 to be done before these relationships can be adequately discussed, but the data, though 

 incomplete, justify the expectation that useful and general relationships will ultimately 

 be established between the conductivity of concentrated solutions of good electrolytes 

 and the character of their ions. 



Some progress has been made towards filling up the gaps indicated by Tables B and 

 C, but further discussion of these relationships must be postponed until some at least 

 of these gaps have been filled up. 



In a paper communicated to the Society in 1897, attention was drawn to increase 

 in electrical conductivity as a characteristic of photo-chemical action, and in a second 

 communication in December of the same year the following statement was made : "It 

 would appear that the chemical behaviour of the acids just mentioned (HN0 3 , HC1, 

 H 2 S0 4 ) depends in many of their reactions on whether their concentration is above 

 or below that corresponding to their maximum electrolytic conductivity." # 



The exact experimental determination of the concentration corresponding to 

 maximum specific conductivity is difficult, owing to the very slight variation of the 

 conductivity with concentration near the maximum. 



Now it is important to note that Table A shows clearly that in all cases where such 



* « = specific conductivity. 

 TRANS. ROY. SOC. EDIN., VOL. XLV, PART I. (NO. 9). 35 



