112 PROF. F. CRACE- CALVERT ON THE 



in a negative electrical condition ? This is a very difficult 

 question to solve. From many observations I have made, 

 I am led to believe that the iron is in a passive state ; and 

 this opinion is based not only on the known data, that a 

 blade of iron is not attacked by strong nitric acid, and that 

 we have no electrical current if one fluid and one metal 

 are brought into contact, whilst if two fluids and a metal, or 

 two metals and one fluid, are employed a galvanic current 

 is generated. My experiments show that not only caustic 

 alkalies possess this peculiar property, but also their car- 

 bonates and bicarbonates; and I hope that the following 

 experiments will throw some light on this point. A blade 

 of polished iron was dipped into a solution of caustic soda, 

 and at each end of the blade was attached a wire communi- 

 cating with a galvano-multiplicator, and no galvanic cur- 

 rent was generated ; and, again, when blades of perfectly 

 polished hoop-iron were placed in bottles half-filled with 

 solutions of caustic alkali, carbonates, and bicarbonates 

 containing from i to 5 per cent, of these compounds, and 

 only a part of each blade was immersed in the solution, the 

 other part being exposed to atmospheric air enclosed in 

 the stoppered bottles, the results were, that after three 

 months neither that portion of the blade dipping in the 

 liquid nor that in the atmosphere was in any way rusted 

 in the solutions containing 5 per cent, of alkali ; and in 

 the experiments with 1 to 2 J per cent., only the part of 

 the blade out of the water was slightly oxidized . 



I was much surprised to find that the carbonates and 

 bicarbonates of the alkalies acted in the same manner as 

 their hydrates in preventing the oxidation of iron, not only 

 on that part of the blade immersed in the solutions but 

 also on that which was exposed to a damp atmosphere of 

 common air. Previously to obtaining these results, I was 

 inclined to believe that caustic alkalies prevented the oxida- 

 tion of iron by absorbing the carbonic acid of the atmo- 



