1 6 ELECTROCHEMICAL INVESTIGATION OF LIQUID AMALGAMS 



various amalgams and mercury were introduced into the four cups. 

 Finally, the electrodes, sealed into narrow glass tubes, were introduced 

 care being taken that the platinum points did not touch the glass. S : was 

 now closed, the coil broken off from the hydrogen supply, and the vacuum 

 connection removed from S 2 . After gentle shaking for several minutes, 

 the completed cell was transferred to the thermostat, and the measure- 

 ments soon begun. 



Amalgams prepared thus remained bright as long as was necessary and 

 showed no signs of oxidation. It is evident that Hulett and De Lury did 

 not fully read the somewhat similar description by Richards and Forbes, 

 or they would not have suggested that the method contained faults which 

 existed only in the preliminary work, not in the procedure finally adopted. 28 



The manner of adjusting the wires connecting the potentiometer to the 

 cell should be mentioned. In the first trials long platinum wires dipping 

 in the various amalgams were connected with the copper wires by means 

 of mercury cups. The junctions of unlike metals were thus outside 

 of the thermostat an objectionable feature. Accordingly, in the final 

 measurements only a short length of platinum wire was fused in the 

 bottom of each tube dipping into the cell, and above this was placed, inside 

 the tube, a drop of mercury. The copper wires were now pushed down the 

 narrow tubes until connection was made with this drop. The contact of 

 unlike metals was now deep in the cell and, being at constant temperature, 

 could cause no disturbance. 



Most of the potentials were measured at 30 and o, and many of the 

 thallium cells were also measured at 15. The temperature of the 30 

 bath was kept constant by means of a sensitive electrical regulator. A 

 large heating coil was used in place of an incandescent lamp as the source 

 of heat, since it avoids any disturbing effect due to radiant energy when 

 the heater is in frequent operation. The temperature of this bath was 

 always constant within 0.01. The 15 bath was exactly similar except 

 that it was equipped with a cold-water coil in order to compensate for the 

 higher temperatures of the surroundings. For the zero bath a metal 

 trough was filled with clean, finely crushed ice, covered with distilled 

 water. This trough was placed in a larger one, the space between being 

 filled with ice, and the box in turn was tightly packed in sawdust. This 

 arrangement gave a very constant temperature. The temperatures of all 

 the thermostats were determined with small Beckmann thermometers, 

 capable of being read to within 0.005 5 tne . v were standardized by com- 

 parison with a very accurate Reichsanstalt thermometer, taking all the 

 precautions necessary for ascertaining the temperature to within o.oi. 



M Compare Hulett and De Lury, Journ. Am. Chem. Soc., 30, 1809 (1908) with 

 Richards and Forbes, Publication of Carnegie Institution of Washington, No. 56, 

 page 40 (1906). 



