40 ENERGY CHANGES INVOLVED IN DILUTION OF AMALGAMS. 



We now resolved to conduct a series of final measurements, repeating all 

 those where amalgams more dilute than No. 2 were concerned, with ex- 

 treme precautions against error. To exclude the last trace of air from the 

 process, the purest mercury was redistilled directly into a pipette as follows : 

 The condenser tube of the all-glass apparatus previously described was fused 

 to the inlet of the pipette, as it lay in a horizontal position. The capillary 

 tip was cut off below the stopcock, and in its place was fused the tube lead- 

 ing to the vacuum pump. The distillation was conducted as usual in a 

 stream of hydrogen until 300 grams of mercury had collected in the hemi- 

 sphere below the inlet and outlet tubes. Then the stopcock was closed, and 

 the system filled with hydrogen. The inlet tube was now fused off into a 

 hook as usual. No important amount of oxygen could have been present in 

 the mercury or its atmosphere. The vacuum connection was now cut off 

 and the capillary tip fused on in its place. The next problem was to replace 

 all the air in the outlet tube with mercury. It will not suffice to hold the 

 pipette upright and open the stopcock, since the mercury will run down into 

 the capillary without filling the intervening section of larger tubing. The 

 elasticity of the confined body of gas will allow mercury to spirt out at every 

 jar, and will make accurate weighing impossible. Therefore, a one-hole 

 rubber stopper receiving the outlet tube of the pipette was fitted into a heavy 

 test-tube side-necked for a vacuum connection and a hydrogen supply. When 

 all the air present had been replaced by hydrogen the pressure was slightly 

 diminished and the tip of the pipette raised somewhat above the bulb ; a 

 column of mercury still clung in the tube connecting the stopcock to the 

 bulb, and on opening the stopcock the mercury slowly rose into the outlet 

 tube and filled it completely. On detaching the test-tube and stopper the 

 pipette containing pure mercury free from oxygen was ready for use. With 

 this pure mercury was accomplished the dilution of amalgams No. 2, No. 22, 

 and No. 9 inside the cell, as follows : 



The Dilution of Amalgam No. 2. Quantitative Data. 



NO. 19. 



Weight amalgam No. a 7732 Ratio of densities 3533 



Weight mercury I3-9<o5 I 3-54 I 



21.717 



1 = 2 _LIL7 IJL533 c = 

 '19 7-732 ^ 13-541' 8 c,9 



