NOTES
4033
The Temperature Coefficient of Conductance of Aqueous Sodium Sulfate around 32.4’
by Robert L. Kay, George A. Vidulich, and Thomas Vituccio
’P
- 125
Mellon Institute, Pittsburgh, Pennsylvania (Received June 22, 1966)
An abnormal temperature dependence of the conductivity of a 0.01 M aqueous sodium sulfate solution has been reported’ for temperatures close to the decomposition temperature of the solid decahydrate. The temperature coefficient between 33 and 34’ was claimed to be only one-third to one-fourth that found at higher and lower temperatures and the break in the conductivity curve between these temperatures was reported to amount to 2.5%. The same type of result has been reported2 for 1% aqueous sodium carbonate solutions in that the change of viscosity with temperature showed two breaks at temperatures corresponding to solid hydrate transitions. We have tried to reproduce the effect by measuring conductivities of 0.01 M SazSOeand 15 wt. % NazSOc in aqueous solution as a function of temperature. The 0.01 M solution was measured in a Kraus-type Erlenmeyer conductance cell with a cell constant of 1.6. The solution was stirred continuously by a magnetic stirrer and Teflon-coated stirring bar. The more concentrated solution was measured in a Pyrex U-tube cell which had a cell constant of 205 and which was fitted with platinized platinum dip electrodes separated laterally by 22 cm. This cell exhibited no detectable frequency dependence within 0.1 ohm between 0.5 and 10 kHz. in the resistance range studied here. A description of the bridge, detector, and method of operation are reported in detail el~ewhere.~The temperature was determined to 0.003’ on a Beckmanri thermometer calibrated by a platinum resistance thermometer and Afueller bridge. The constant temperature oil bath was regulated to f 0.005’. The resulting conductivities of the solutions are shown in Figure 1. Within 0.1% the conductivities of the 0.01 M solution are linear in the temperatures between 31 and : 3 4 O and the points for the 15 wt. % solution fall on
