226 



Royal Society : — 



gives 545 millionths. The third band was situated at about the 

 same distance from the middle band on the more refrangible side. 



It would appear that this comet is similar in constitution to the 

 comets which I examined in 1868*. 



June 15. — General Sir Edward Sabine, K.C.B., Pres., in the Chair. 



The following communication was read : — 



" On a Law in Chemical Dynamics." By John Hall Gladstone, 

 Ph.D., F.R.S., and Alfred Tribe, F.C.S. 



It is well known that one metal has the power of decomposing 

 the salts of certain other metals, and that the chemical change will 

 proceed until the more powerful metal has entirely taken the place 

 of the other. The authors have investigated what takes place during 

 the process. 



The experiments were generally performed as follows : — 72 cubic 

 centimetres of an aqueous solution of the salt of known strength, 

 and at 12° Centigrade, were placed in a tall glass ; a perfectly clean 

 plate of metal of 3230 square millimetres was weighed and placed 

 vertically in this solution without reaching either to the top or bot- 

 tom ; the action was allowed to proceed quietly for ten minutes, when 

 the plate was removed, and the deposited metal was washed off. The 

 loss of weight gave the amount of metal dissolved, and represented 

 the chemical action. 



The most complete series of results was with copper and nitrate of 

 silver. 



Nitrate-of-silver 

 solution. 



Copper dissolved. 



Theo- 

 retical. 



Differ- 

 ence. 



Propor- 

 tional 

 number. 



Percentage 

 of salt. 



Actual weights. 



Average. 



1. 



3541 



0-0045, 0-0050 



00475 



0-00455 



+0-0002 



2. 



0-7083 



00135, 0-0140 



0-01375 



0-01365 



+0-0001 



s! 



1-0623 



00240, 0-0250 



0-0245 



0-0259 



-0-0014 



4. 



1-4166 



0-0420 



00420 



0-0409 



+0-0011 



5. 



1-7705 



0-0600 



0-0600 



0-0583 



+0-0017 



6. 



2-1246 



0785 



0-0785 



00790 



-0-0005 



7. 



2-4788 



00975 



0-0975 



0-0994 



-00019 



8. 



2-8332 



0-1230, 0-1230 



0-1230 



0-1228 



+0-0002 



9. 



3-1873 



0-1510, 0-1480 



0-1495 



0-1481 



+0-0014 



10. 



3-5415 



0-1680, 0-1670 



0-1675 



0-1749 



-00074 



11. 



3-8956 



01955 



0-1955 



0-2035 



-0-0080 



12. 



4-2497 



0-2170, 0-2285, 0-2310, 0-2200 



0-2241 



0-2336 



-0-0095 



14. 



4-9580 



0-2740 



02740 



0-2982 



-0-0242 



16. 



5-6664 



0-3270 



0-3270 







20. 



7-0830 



0-4540, 04100 



0-4320 







24. 



8-4994 



0-5400 



0-5400 







30. 



10-624 



0-6850 



0-6850 







32. 



11-333 



0-7100 



0-7100 







40. 



14-166 



0-8440, 0-9090 



0-8765 







48. 



16-999 



1-0690 



1-0690 







60. 



21-246 



1-359 



1-359 







70. 



24-788 



1-580 



1-580 







Phil. Trans. 1868, p. 555; and Proc. Eoy. Soc. vol. xri. p. 386. 



