Effluvia from Chemical or from Voltaic Reactions. 25 



subsequently positive, as in Mr. Enright's experiment. The 

 conditions here also were not sufficiently distinct. 



A strip of zinc 10 centim. long by about 1 wide had a 

 gutta-percha-covered copper wire soldered to it and the joint 

 protected by a covering of gutta-percha. It was then bent 

 into a spiral to lie on the bottom of the small beaker, the wire 

 rising vertically from it. It was cleaned but not amalgamated, 

 and was covered to a depth of 1J centim. with strong zinc- 

 chloride solution. A bent copper sheet was then clamped 

 to the wire with its lower edge about 1 centim. above the 

 zinc chloride, and a solution of hydrochloric acid, con- 

 taining 20 per cent, strong acid, was carefully poured in 

 until it rose 2 or 3 millim. on the copper. Gas was 

 sluggishly evolved from the copper, and the deflexion altered 

 about 3 divisions in 12 minutes, apparently indicating a 

 feeble negative electrification of the cell. In a second experi- 

 ment, using a 5-per-cent. acid solution, the cell seemed feebly 

 positive, the index moving 10 divisions in half an hour. 

 But the results of both trials are so small as to be incon- 

 siderable. 



10. The copper w T as now removed and replaced in a new 

 experiment by a piece of zinc cut from the same sheet 

 as that already in the cell, but not cleaned, in order that it 

 might be less active towards the liquid and represent b in 

 fig. 2. 



Its lower edge was about 3 centim. above the zinc- 

 chloride solution, and was immersed to a depth of 5 millim. 

 in a mixture of 1 part strong hydrochloric acid with 4 of 

 water. Gas was sluggishly evolved from the upper zinc and 

 the spot moved in 7-J minutes to 35, cell positive. It then 

 returned and the cell became negative, 110 divisions, when 

 the experiment was stopped. 



11. The experiment was repeated with a 10-per-cent. acid 

 solution, with the interesting results given in tabular form 

 below, where the first column indicates the number of minutes 

 which elapsed after immersion of the upper zinc in the acid 

 solution, and the second the potential of the cell, positive or 

 negative, in scale-divisions as indicated by the electrometer. 

 No gas was evolved from the lower zinc. 



5 +18. Gas sluggishly evolved from upper zinc. 

 11 +75. Striae of ZnCl 2 solution streaming down from 

 upper zinc. Kather brisker gas-evolution. 



15 +101. 



16 +? Positive electrification reaches limit and begins to 



fall. Probably local action at upper zinc begins 

 to predominate and the Enright effect supervenes. 



