154 AGRICULTURAL CHEMISTRY 



The more electro-positive elements replace those which are less 

 electro-positive. Observe in these experiments that the copper is 

 coated with silver, the lead with copper, and the zinc with lead. 

 Write the following reactions which have taken place : 



(1) AgN0 3 + Cu = 



(2) Cu(N0 3 ) 2 + Pb = 



(3) Pb(N0 3 ) 2 + Zn = 



Questions. ( i ) Which element is the most positive ? ( 2 ) What 

 elements can zinc replace ? (3) Why does copper replace silver? 

 (4) Wny does lead replace copper ? (5) What does this experi- 

 ment show as to the relative properties of the three elements, cop- 

 per, silver and lead ? 



