of' preserving Iron from Corrosion in Sea-water. 53 



subject, of the same opinion as myself. In an article " On 

 some recent Experiments, made with a view to protect Tln-Plate 

 or Tinned-Iron from corrosion in sea-water," inserted in the 

 London and Edinburgh Philosophical Magazine, Nov. 1835, p. 

 391, we read : — " If a piece of tin-plate is exposed in sea-water 

 for a few days, it will exhibit an incipient oxidation, which will 

 gradually increase ; the tin will be preserved at the expense of 

 the iron, which will be corroded ; but if a small surface of zinc 

 is attached to a piece of tin-plate and Immersed in sea water, 

 both the tin and iron will be preserved, whilst the zinc will be 

 oxidated." 



The following experiments, in which an accurate weighing of 

 the metals had taken place, communicated to me, by my friend 

 Mr G. T. Mulder of Rotterdam, are also in perfect accordance 

 with my own experience. 



1. A plate of iron, weighing 32.907 grs., was placed in a glass 

 vessel containing one litre of sea-water, during twenty day?, 

 at the temperature of the month of November of last year. 



After the experiment the weight of the iron was found to 

 be, 32.726 grs. ; loss by oxidation, 0.181 grs. 



2. A similar plate of Iron, exactly of the same weight of 32.907 

 grs., but on whose surface was fixed a small piece of tin weigh-- 

 ing 8.140 grs., was in the same manner exposed during tAventy 

 days, in one litre of sea-water. 



The weight of the iron after the experiment was found to be, 

 32.074 grs. ; that of the tin, 8.139 grs.; loss by oxidation of 

 the iron, 0.233 grs. ; loss by oxidation of the tin, 0.001 grs. 



The results of these experiments shew, that the iron, when 

 exposed alone to sea-water, had lost 0.052 grs. less than that 

 whereon was fixed a small surface of tin, whilst the tin had lost 

 but 0.001 grs. This trifling loss of the tin must necessarily have 

 taken place in the first moments of immersion in sea-water; 

 whilst the primitive electrical relation between both metal?, which 

 they acquired in the atmosphere, was not yet changed. This 

 part of the experiment seems evidently to confirm what was ob- 

 served by means of galvanometrical researches. 



A. Van Beek. 



Utbecht, January 1837. 



