202 ELECTRICAL RESISTANCE OF ACETIC ACID 



decreasing temperature. The true temperature effect 

 is to make the resistance increase with decreasing temper- 

 ature, but as the temperature coefficient of this licjuid is 

 small, the shape of the curve is not materially affected by 

 this factor. 



From the temperature of the bending point, down to the 

 eutectic point, the resistance increases with the decreasing 

 temperature. At the eutectic point, (-26.55°C)\ the sol- 

 ution of water in acetic acid suddenly becomes solid, this 

 mixture containing 59% of solid acid and 41% of ice. A con- 

 siderable change in the resistance of the tube might be expec- 

 ted to occur at this temperature, and as the temp, is further 

 decreased, the solid mixture should be found to have a true 

 temperature coefficient. 



To verify the last supposition, the resistance tube was 

 surrounded by solid carbon dioxide and a temperature of 

 — 80°C" was finally obtained. This was measured by means 

 of a thermocouple placed in the oil bath. As the temp, de- 

 creased rapidly it was noted that at some temperature between 

 — 25° and — 30°C the resistance suddenh^ increased from approx. 

 8 X 10^ to a value impossible to measure in the "network"' 

 The tube was then connected with an electrometer and con- 

 denser, as shown in figure 2. When the temperature of the 

 resistance tube became equal to the temp, of the surrounding 

 solid COo. -80°C, an E. ^l. F. was applied and the current 

 passing thru the acetic acid was measured bj' the electrometer. 

 The specific resistance of sample I was found equal to 1.00 x 

 lO^' (« -80°C. Another sample Xo. 2, somewhat purer than 

 No. I, was measured in a different tube (^ -80°C and had a 

 value of 9.92 x 10^-. Sample 2 was removed from the sur- 

 rounding CO2 and placed in a Dewar bulb. As the tube 

 heated, resistance measurements were made at intervals, the 

 thermocouple being read at the instant an electrometer 



1 Dahms, Wied. Ann 60, 123, 1897. 



2 Landolt und Bornstein, Tabellen page 76. 



