3 i6 SCIENCE PROGRESS 



this is his belief is clear from many passages in chapter xiv., 

 such as the following, for example : 



" It may be well, therefore, at the outset to make perfectly 

 clear what should be meant by the term galvanic and then 

 to try and determine in how far galvanic activity may be said 

 to effect the rate of corrosion of metals (p. 238). 



" Reverting to the simple cell composed of copper and iron 

 plates immersed in dilute sulphuric acid, we see that, as the iron 

 dissolves, chemical energy is set free ; the chemical equation 



Fe + H 2 S0 4 = FeS0 4 + H 2 



is therefore incomplete in so far that it takes no notice of this 

 energy. When the iron is isolated, that is to say when it is 

 allowed to dissolve in the acid, not being in contact with any other 

 metal (my italics), this chemical energy is set free almost entirely 

 as heat (p. 239)." 



It is extraordinary that such loose doctrine should prevail 

 even at the present day— that it should be possible to disregard 

 fundamental principles so entirely: until clearer views obtain 

 as to the nature of the initial change whenever iron is attacked, 

 it will be useless to attempt to discuss the more complex issues. 

 But the confusion obvious in the passages subsequent to that 

 last quoted is even greater. 



" The bulk of this heat is lost by radiation and in increasing 

 the temperature of the sulphuric acid and the containing vessel. 

 If we can so arrange matters that the loss by radiation is 

 entirely avoided and the amount of heat absorbed by the con- 

 taining vessel and acid in raising the temperature through each 

 degree is reduced to a minimum, the actual rise in temperature 

 will become relatively great, with the result that the amount 

 of iron dissolved in unit time will be proportionately increased. 

 In practice, however, the loss by radiation is so great, and 

 the heat capacity of the surrounding medium so large, that in 

 general no very great rise in temperature may be observed 

 and the iron dissolves at a relatively uniform rate. Almost the 

 same result as is obtained by raising the temperature may be 

 arrived at by connecting the iron with the copper by means of a 

 wire. Part of the chemical energy liberated by the solution of 

 the iron is now converted into electricity which is not lost by 

 radiation as was the heat, but stimulates the chemical action in a 

 similar manner as an equivalent rise in temperature. Conse- 

 quently the iron passes more rapidly into solution even though 

 the temperature remains substantially the same. It follows 



