A Note ofM. A. Van Beek. 43 



the subject, doubts arose of its accuracy. It appeared very un- 

 likely that an inquirer such as my brother, who had devoted 

 so much time to electro-chemical research, and had just then 

 brought to a conclusion the investigation of the protection of cop^ 

 per in sea-water by electro-chemical means, should have fallen in- 

 to so grave an error ; and considerations respecting the relation 

 of tin to iron in the scale of chemical affinities, came in confir- 

 mation of this opinion. To endeavour to satisfy myself, as far 

 as possibly to demonstration, on which side the truth was, I 

 had recourse to experiments ; and I now beg leave to commu- 

 nicate some of the results, with the conclusions to which they 

 led. 



If M. Van Beek were correct, it appeared as a necessary 

 consequence, that tin would be negative in its electrical rela- 

 tion to iron. To ascertain the relation of these two metals in 

 this particular, I connected wires of them with a galvanometer, 

 and plunged them successively into the mineral acids, more or 

 less diluted with water, into sea-water, solution of potash, and 

 lime water. The result in every instance was the same ; the 

 tin proved positive and the iron negative. 



Tin thus being positively electrical in relation to iron, it ap- 

 peared a necessary consequence, that it should exert a protect- 

 ing influence on the iron, and defend it from chemical action. 

 To ascertain this, three equal portions of tin wire were taken, 

 and three of steel wire, each weighing 1.6 grain, and muriatic 

 acid of the same dilution, in about equal quantities, was poured 

 into similar vessels. 



Into one of these a tin wire alone was put, into another a 

 steel wire alone ; into a third, a steel wire and tin wire twisted 

 together. 



In less than twelve hours, the steel wire unattached was dis- 

 solved. After three days, the tin wire was found to have lost 

 six-tenths of a grain, and the same both in the instance in which 

 it was alone, and in that in which it was connected with the 

 steel ; but, the steel in this latter instance had lost nothing, it 

 retained its lustre unimpaired, and, in brief, was perfectly pro- 

 tected by the tin. And the same result was obtained when the 

 tin and steel wires were boimd together by a fine silver wire. 



The next necessary consequence appeared to be that tin 



