218 JONES AND SCHUMB. 



temperature, in an atmosphere of nitrogen. A wide-mouthed bottle 

 holding about 800 cc, was provided with a rubber stopper, perforated 

 by four holes. Through the central hole passed a glass bearing, con- 

 taining a closely-fitting brass tube, into which was affixed a glass 

 stirrer (A), which was rotated by a small motor, the vertical shaft of 

 which was attached to the stirrer by several inches of flexible, stout 

 rubber tubing. The bearing was made gas-tight by means of a mer- 

 cury seal. Through a second hole in the stopper passed an inlet tube 

 for nitrogen gas. Two other tubes, serving respectively for the outlet 

 of the gas or of the solution, passed through the remaining holes of the 

 stopper, and were combined tlirough a T-joint into a single tube, which 

 entered the cell itself. This bottle was completely immersed in a 

 thermostat at 25.00° during the saturation, and pure atmospheric 

 nitrogen gas was permitted to bubble through the solution during this 

 process. For the work at 0°, the bottle and cell were buried in a large 

 tub of cracked ice and water. The stopper of the bottle was thor- 

 oughly coated with paraffine before immersion, to render it water- 

 tight. The stirrer was usually allowed to run over night, while a 

 slow current of nitrogen swept through both the bottle and the cell in 

 order to ensure saturation of the solution and absence of oxygen. 



The nitrogen generator was kindly loaned us by Dr. A. T. Larson. 

 The removal of the atmospheric oxygen was accomplished in the cold 

 by cuprous ammonium carbonate solution, which was circulated by 

 means of air-lifts through two towers filled with copper chips and 

 gauze. The removal of oxygen is practically complete after passage 

 of the air through the first column; as shown by the fact that the 

 absorbing liquid in the second column remained practically colorless 

 at all times. This generator w^ould deliver a slow stream of gas for 

 many hours, and was frequently allowed to run over night without 

 any attention. 



The cell was of special design, shown in Figure 4. The purpose of 

 the apparatus was to permit the plating out of metallic thallium 

 electrodes from a solution of thallous chloride, in the absence of oxygen, 

 and also to permit the rinsing of the cell without access of air, and the 

 refilling of the electrode vessel with thallous cliloride solution of 

 definite concentration, as prepared in the saturation bottle. A is the 

 inlet tube for either nitrogen or the solution. If the three-way cock, 

 D, is properly set, and the stopcock of F is open, both the chamber, B, 

 which is used as the anode chamber during the plating out of the 

 thallium electrodes, T, and C, the cathode chamber in this operation, 

 may be filled at the same time. The arrangement shown avoids the 



