T HE 

 LONDON, EDINBURG-H, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



AUGUST 1891. 



XXIII. Chemical Action at a Distance. By Prof. W. Ostwalp*. 



APIECE of amalgamated zinc, as is well known, is not 

 attacked by dilute acids ; if, however, a platinum wire 

 be wound about it, solution in the acid takes place at once 

 with evolution of hydrogen. Zinc, armed with platinum, 

 cannot be dissolved in solutions of neutral salts, as, for 

 instance, potassium sulphate ; if a few drops of acid, as sul- 

 phuric acid, be added to the liquid, solution again ensues. 



For the platinum to exercise its action, it is only necessary 

 that it remain in contact with the zinc at a single point. If 

 zinc and platinum be made into a curved piece, with its arms 

 some slight distance apart, and these be so placed in a 

 potassium-sulphate solution that the portions of the liquid 

 surrounding each arm are separated by a wall of porous 

 material, such as unglazed earthenware or parchment-paper, 

 then the question can be decided which metal, zinc or pla- 

 tinum, must come in contact with the acid that solution may 

 result. 



At first sight the question seems absurd ; for since the zinc 

 is to be dissolved, it seems self-evident that the acid belongs 

 with the zinc. However, if the experiment be tried, one 

 finds exactly the reverse : the zinc does not dissolve (with the 

 exception of traces which would go into solution in any event) 

 when the potassium-sulphate solution about it is acidified ; it 



* From the Sitzimgsberichte der Kgl. Sachsischen Gesellschaft der 

 Wissenschaften for 1891, communicated bv the Author. Translated bv 

 J. E. Trevor. 



Phil Mag. S. 5. Vol. 32. No. 195. August 1891. L 



