138 KOLLOCK-SM1TH — ELECTRO-ANALYSIS. [April 13 



The anode, 7.5 cm. in length, is made from platinum wire 1 

 mm. in diameter, coiled into a flat spiral 1.5 cm. in diameter. It 

 is inserted in a chuck carried by the rotator which is also provided 

 with three pulleys varying from 2 to 5 cm. in diameter. These 

 pulleys are connected by a belt to two pulleys on the motor. 

 With this arrangement the rotation of the anode could be varied 

 from 100 to 1800 revolutions per minute. During the decom- 

 position an amperemeter, a voltmeter and a rheostat, allowing of 

 resistance from .1 to 100 ohms, were kept in the circuit. 



The precautions indicated by Myers in his paper with regard to 

 the decomposition cell were observed. If care be taken to have the 

 cell as clean as possible there will be no trouble experienced with 

 the amalgam subsequently adhering to its sides. The mercury, be- 

 fore using, should be washed with alcohol and ether and after the 

 odor of the latter has disappeared, be placed in the desiccator until 

 it is weighed. It was generally allowed to remain for about five 

 minutes on the balance pan before taking the final weight. In prac- 

 tice a beaker containing a large quantity of mercury, so prepared, 

 should be kept in the desiccator ready for use. The mass of the 

 mercury taken in a single experiment varied from forty to fifty grams. 

 This was frequently used for two or three determinations, except 

 in the case of chromium, where it was found advisable to use it 

 but once. The cathode surface in the first experiments upon zinc 

 was 3.5 sq. cm., but throughout the rest of the work it was about 

 9 sq. cm. After weighing the decomposition cell and mercury, 

 the solution to be electrolyzed should be introduced. The volume 

 of the electrolyte is always recorded in the accompanying tables. 

 The cell should then be placed upon the copper plate and the 

 anode lowered into the solution. The distance between the 

 cathode and anode depended upon the volume of the electrolyte. 

 When the volume was five cubic centimeters the electrodes were .5 

 cm. apart and in other instances 1 cm. was their distance apart. 

 The difference did not appear to materially affect the rate of 

 deposition. The tube should be covered. The anode should next 

 be rotated and the connection made with the required number of 

 chloride accumulator cells. The speed of the anode was varied 

 either by using less current for the motor or by changing the com- 

 bination of pulleys. With the higher currents recorded, the solu- 

 tion was frequently heated to boiling. When this occurred the 



