10 Dr. V. Novak on the Specific Electric Conductivities and 



To test this, I measured the electric conductivity of a 

 series of formic acid solutions which contained only a small 

 amount of water, the freezing-point of every solution being 

 observed. 



The formic acid was obtained from Harrington (London) ; 

 its freezing-point was 1°'47. I treated this acid according 

 to the method given by W. Saposchnikoff *, and I prepnred, 

 by repeated distillation and recrystallization, an acid which 

 froze at 7°*76. 



The electric measurements were made by F. Kohlrausch's 

 method by means of Wheatstone's bridge and telephone. 

 The alternating current was the town supply, which was 

 sent through the longer coil of a transformer, the shorter coil 

 being connected with the ends of the bridge. 



The resistance-cell was so arranged that it was possible to 

 use only a small amount of the liquid. A tube ground on the 

 top was closed by another ground-glass ring, which was 

 cemented to a plain thick glass plate through which two 

 insulated platinum electrodes passed. The Fig. 1. 



apparatus is shown in fig. 1. 



I preferred this form to those of Kohl- 

 rausch or Arrhenius because the distance 

 between the electrodes was absolutely con- 

 stant, and the cleaning of the tube and flushing 

 and drying of the electrodes was extremely 

 easily done. 



The minimum of the sound in the telephone 

 was very sharp if the resistance used was some 

 hundred ohms. If smaller resistances were 

 used, a condenser of suitable capacity had to 

 be added on the side of the rheostat. 



The resistance-cell was put, in a larger 

 vessel filled with water, stirred by a mecha- 

 nical stirrer, the temperature being measured 

 by two mercury thermometers. 



The resistance-cell was calibrated with a 



N 

 -— . solution of potassium chloride, the specific molecular 



conductivity of which was adopted as 1147 . 10 _8 f in terms 

 of mercury. The distilled water used had a conductivity 

 0*9 . 10 -10 , which (according to Kohlrausch's Leitfaden d. 

 prakt. Physik, viii. Aufl. 1896) may be considered as very 

 low. 



The freezing-points of different solutions were observed by 



* W. Saposchnikoff, Journ. rusk, jihys. chem. Ges. 25. ii. p. 626 (1893). 

 t Kohlrausch, Wied. Ann. xxvi. p. 195. 



