( 205 ) 



XII. — On the Relative Electro-Chemical Positions of Wrought Iron, Steels, 

 Cast Metal, &,c, in Sea- Water and other Solutions. By Thomas Andrews, 

 Assoc. M. Inst. C.E., F.C.S. (Plates XXX. to XXXIV.) 



(Read 15th January 1883.) 



The experiments contained in this memoir were made by the author with 

 the galvanometer on wrought iron, steel, cast metal, &c, bars and plates, 

 arranged in galvanic circuit in sea- water and various other waters and solutions, 

 to determine the relative electro-chemical position of these metals under such 

 circumstances. 



These varieties of the same metal iron are of such vast and universal utility 

 that accurate information respecting any of the properties possessed by them 

 cannot fail to be of interest. 



A knowledge of the relative electro-chemical positions assumed by wrought 

 iron, steels, and cast metal when in galvanic connection in sea-water is of 

 importance as determining their respective liability to electrolytic disintegration 

 when combined in marine works and structures, and a research of this kind 

 presents features of interest capable of practical application in many ways. 



When plates or bars of wrought iron, steel, &c, are connected in circuit 

 and immersed in sea-water or other solution, and attached to a delicate galva- 

 nometer, an electric current is set up of varying power according to the 

 difference of chemical composition or mechanical or physical projDerties, &c, of 

 the wrought iron and steels employed. 



The following experiments were undertaken by the author to measure, if 

 practicable, the extent of this action, and to endeavour to determine the relative 

 electro position of the various steels, wrought iron, and cast metal, with some 

 degree of exactness. 



Table A. 



Analyses of Steel, Wrought and Cast-Iron Bars. Percentage Composition. 



Description. 



Graphitic 

 Carbon. 



Combined 

 Carbon. 



Silicon. 



Sulphur. 



Phosphorus. 



| 



Manganese. 



Tun 



gsten. 



Iron 

 (by difference). 



Soft Siemens- Martin stee 



1, ... 



















Wrought iron, 





Trace 



•224 



None 



•239 



•071 







99-466 



Soft steel (Firth's), . 





•570 



•032 



Trace 



•066 



•147 







99-185 



Bessemer steel, 





•550 



None 



•032 



•175 



•216 







99-027 



Puddled steel, 





•440 



•144 



•048 



•149 



Trace 







99219 



Puddled steel (chilled), 





•490 



•140 



•004 



•073 



•215 







99-078 



Hard steel (Firth's), 





1-600* 



■145 



•002 



•025 



•183 







98-045 



Cast metal, 



2-400 



1-000* 



•570 



•140 



•580 



•860 







94-450 



Tungsten steel, 





1-750* 



•135 



•069 



•139 



■720 



9- 



270 



87-917 



By combustion. 



VOL. XXXII. PART T. 



2 L 



