Van Beek 07i a Supposed Property of Tin. 4-7 



phrey Davy, recommending the use of tin for preserving the 

 iron-boilers of steam-vessels from corrosion by sea- water ; and to 

 shew that I was in error in the remarks which I had made. 



The article by Dr Davy is written with all the moderation 

 and politeness which ought to characterize the refined culti- 

 vator of science ; and such being the case, it becomes a real plea- 

 sure to discuss a disputed point with candour and impartiality. 



Being myself a true admirer of the eminent merits of the 

 late Sir Humphrey Davy, whose discoveries, with regard to 

 their useful application in navigation, I have endeavoured my- 

 self strongly to promote among my countrymen ; it was nei- 

 ther hyper-criticism nor unfounded suspicions, but only the love 

 of truth, that directed my pen in writing the note in question. 

 Moreover, being fully convinced, from accurate and decisive 

 experiments, I thought it my duty to warn those who, on the 

 authority of Sir Humphrey Davy, might employ tin instead of 

 zinc to protect the iron-boilers of steam-vessels from corrosion 

 by sea-water. I resolved, nevertheless, to re-examine, with the 

 utmost care and impartiality, the whole question, and to pub- 

 lish whatever might be the result of my investigation. 



The following experiments were made on this subject : — 



1. A piece of iron, of 65"'" square, was placed in a cylindri- 

 cal vessel containing about half a litre of sea- water, and the iron 

 was quickly corroded. After forty-two days the whole plate 

 was oxidated, and a strong precipitate of oxide of iron lay at 

 the bottom of the glass-vessel. 



2. A similar plate of iron, on the surface of which was at- 

 tached a small piece of tin of 23™" square, was at the same 

 time exposed to a similar quantity of sea- water. In a few days 

 the iron was strongly oxidated ; and the sea-water turned to a red 

 colour owing to oxide of iron, which increased every day, and 

 formed, as in the first experiment, a thick sediment at the bot- 

 tom of the glass; whilst the tin, as far as its surface was not co- 

 vered by precipitated oxide of iron, remained bright, which was 

 principally to be observed on the sides or edges of the small 

 tin plate, on which the oxide of iron could not remain station, 

 ary. In forty-two days the quantity of oxide of iron in this 

 vessel was by no means less than that of the preceding expe- 

 riment. 



