1872.] 



Decomposition of Water by Zinc. 



219 



temperature. Thin sheets of zinc and copper were hammered together 

 and placed in a bottle filled with distilled water. Small bubbles of gas 

 were formed. The experiment, however, was tried in a more perfect form. 

 Some zinc-foil was allowed to remain in a somewhat dilute solution of 

 copper sulphate until its surface was well covered with spongy copper. 

 The metals were thoroughly washed with distilled water, and then they 

 were immersed in a bottle of distilled water with a delivery-tube. Minute 

 bubbles of gas quickly made their appearance, which proved to be hv- 

 drogen, and zinc-oxide was formed. Two experiments were made quanti- 

 tatively, the gas being collected and measured at the end of 24 or 48 hours. 

 The quantity of gas in cubic centimetres is given in the third and fourth 

 columns of the subjoined Table, corrected for temperature and pressure. 

 The mean temperature in the second column is simply the mean of the 

 maximum and minimum during the period. In experiment A, 33*4 grms. 

 of zinc-foil were employed, being 2*6 metres long and 05 wide. The 

 coils were kept apart by muslin. In experiment B there was used 1 metre 

 of similar foil crumpled up. 



Day. 



Mean 

 temp. 



Exper. A. 



Exper. B. 



Day. 



Mean 

 jtemp. 



Exper. A. 



Exper. B. 





C. 



c. c. 



c. c. 





C. 



c. c. 



c. c. 



h 



12-8° 



1171 



49-6 



18. 



6-7° 



20-0 



7-6 



2. 



12-2 



93-8 



37-5 



19, 20. 



64 



17-2 (X 2) , 



5-7 (x2) 



3. 



11-7 



73-8 



27-6 



21. 



4-4 



20-0 



6-6 



4. 



11-1 



66-2 



247 



22. 



50 



15-3 



4-8 



5, 6. 



10-0 



49-3 (x 2) 



17-5 (x 2) 



Interval. 









7. 



8-9 



411 



14-9 



44. 



10-0 



20-5 



5.5 



8. 



10-5 



40-9 



15-8 



45, 46. 



10-5 



22-5 (X 2) 



6-5 (x 2) 



0. 



100 



409 



14-8 



47. 



11-1 



223 



65 



10. 



7-8 



338 



103 



48. 



11-1 



24-1 



8-1 



11. 



6-7 



28-0 



9-4 



49. 



11-1 



20-5 



74 



12, 13. 



61 



21-9 (X2) 



7-7 (X2) 



Interval. 









14. 



64 



20-1 



76 



82. 



100 



18-0 



4-7 



15. 



7-2 



311 



103 



83. 



100 



18-9 



61 



16. 



100 



30-0 



10-2 



84. 



10-0 



140 



51 



17. 



8-3 



29 4 



8-5 











The two experiments have evidently gone on almost pari passu for 

 months, the amount of hydrogen evolved gradually diminishing, but show- 

 ing, at the same time, a certain dependence on the heat of the day. 



Under the microscope the bubbles of gas are seen to form, not on the 

 zinc, but among the copper crystals, and sometimes to make their appear- 

 ance on the. glass at some distance off. 



From the position of platinum in the electro-chemical series we antici- 

 pated that the effect would be still more marked with that metal in a 

 spongy state on the zinc. It was deposited from the tetrachloride, and, 

 of course, thoroughly washed. There was only 0*6 metre of foil, but the 

 following quantities of hydrogen were obtained : — 



