PLATE 23 



No. 1. .0000014 M. Fe 2 (S0 4 ), 

 No. 2. .0000028 M. Fe 2 (S0 4 ) 3 

 No. 3. .0000070 M. Fe 2 (S0 4 ) 3 

 No. 4. .000014 M. Fe 2 (S0 4 ) 3 

 No. 5. .00007 M. Fe 2 (S0 4 ) 3 

 Control. 



[240] 



