Electric Conductivities of Solutions of Water in Formic Acid. 9 



normal electrolytic liquids. This difference is less marked in 

 the case of formic acid, but, even there, a true difference in 

 kind seems to exist, and it is probable that no true ionization 

 of the water occurs. In order to test this conclusion we may 

 make use of the freezing- point determinations which have 

 already been described. 



It was found that 0*5 gram of water depressed the freezing- 

 point of 25*99 grams of strong formic acid by 2°'7. This 

 quantity of water corresponds to 1'07 gram-molecule in 

 1000 grams of solvent, so that 1 gram-molecule in the same 

 weight of solvent would give a depression equal to 2°'52. 

 On the assumption that there is no ionization, van'fc Hoff's 

 formula gives 2°*84 for this molecular depression, and Raoult's 

 experimental results for various organic substances dissolved 

 in formic acid vary from 2° 6 to 2 9. The phenomena of 

 the freezing-points thus confirm our previous conclusion that 

 water dissolved in formic acid is not ionized. 



Nevertheless, such a solution possesses considerable con- 

 ducting power, of which an explanation is required. Possibly 

 it is due to the distribution through the general non-conducting 

 or badly conducting mass of a small quantity of what may be 

 considered a solution of acid in the water which has been 

 added. The curves, however, indicate that such a state is 

 essentially different from that which holds in a normal 

 electrolytic solution. 



In conclusion we may say that there seems to be con- 

 siderable evidence to show that, if a liquid could be found 

 possessing a dielectric constant higher than that of water, it 

 would, when used as a solvent, cause water dissolved in it to 

 be ionized, and give it a conductivity depending on the 

 amount of such ionization and on the ionic fluidity. The 

 conductivity curve would then have the same general form as 

 those which we have seen to be typical of solutions of 

 electrolytes. 



II. Specific Electric Conductivities and Freezing-points of 

 Solutions of Water in Formic Acid. By Dr. Vladimir 

 Novak, Privatdocent of the Bohemian University in 

 Prague *. 



I was induced to do this work by Mr. W. C. D. Whetham 

 (Trinity College, Cambridge), who found in some experi- 

 ments that formic acid, if it contains a small quantity of 

 water, shows extremely simple changes in its specific electric 

 conductivity and freezing-point. 



* Communicated by Prof. J. J. Thomson, F.R.S. 



