22 



ENERGY CHANGES INVOLVED IN DILUTION OF AMALGAMS. 



three times, one of the glass rods was removed and the tip of the solution 

 pipette inserted while hydrogen was issuing from the fine opening. The 

 issuing stream of hydrogen prevented the diffusion of air into the cell. 

 When the body of the cell was about half full, the solution pipette was with- 

 drawn and the various amalgam pipettes successively inserted in the tubes 

 B, C, D, E. Suitable portions of the amalgams were run in. Finally the 

 platinum electrode wires, sealed into tapering glass tubes, were introduced, 

 and the cell was ready for use. 



Fig. 4. Amalgams in Cell Ready for Potential Measurement. 



The temperature of the thermostat was kept constant within a hundredth 

 of a degree by the familiar electrical regulating device shown in the dia- 

 gram (figure 5). The mercury column, instead of cutting off a gas supply 

 at Q, cuts off the current through the incandescent lamp hung in the water 

 until the water cooled sufficiently to allow the circuit to be broken again 

 at Q. An efficient centrifugal stirrer operated by a small electric motor 

 kept the water in rapid circulation. The variation in temperature noted on 

 a sensitive Beckmann thermometer graduated to one-hundredth never ex- 

 ceeded five one-thousandths of a degree. Although it was not important to 

 know the temperature of the cell within nearer than 0.05 it was nevertheless 



