1888.] Electro-chemical Effects on Magnetising Iron. 167 



The Electro-chemical Effect in Relation to the Passive State of Iron. 



Soon after commencing Part I of this research I conceived that 

 the passive state of iron in strong nitric acid would either to some 

 extent be affected, or perhaps overcome, by magnetic influences of a 

 similar nature to those in the experiments on which I am engaged. 

 Preliminary experiments were made and interesting results obtained 

 in connexion with the influence of magnetisation on the action of 

 strong nitric acid on iron and steel. I have obtained, under certain 

 conditions, currents flowing from a magnetised bar to an unmagnetised 

 one in strong nitric acid (sp. gr. 1*42). The currents representing 

 an E.M.F. varying, according to circumstances, from about OOll volt 

 and upwards. After considerable experimentation I feel convinced 

 that induced local currents of the nature of those shown above in 

 Table D were instrumental in causing the magnetised bars to be more 

 acted upon than the unmagnetised ones in the strong nitric acid 

 (sp. gr. 1*42), and such currents are essential in reducing the 

 passivity of iron in nitric acid. 



I hope to have further communications to make with respect to 

 this interesting part of my research. 



In Parts I and II of this research, the results of a quantitative 

 study of these magneto- chemical phenomena have been recorded, the 

 effect in connexion with a considerable variety of typical reagents 

 having been carefully observed. With some reagents the effect was 

 found to be comparatively small, in other instances it was very con- 

 siderable, as in the case of bromine, many of the salts of copper, 

 nitric acid, and similar strong corrosive solutions. The result was 

 dependent both on the strength of the solution and on the extent of 

 the magnetisation of the metal. In most cases with powerfully 

 oxidising reagents the effect was of an electro-positive nature, but 

 in a few other instances (such as H 2 S0 4 , HC1 dil., Fe 2 Cl 3 with 

 chlorine) the reaction partook of a negative character in relation to 

 the electro- chemical position of the magnetised bar. . It is not easy to 

 account for these variations in the nature of the effect ; I think, how- 

 ever, it may be surmised that in these exceptional instances the 

 results were possibly to some extent influenced by the diamagnetic 

 properties of some of the solutions, or of the gases evolved therein. 

 In some of the compound solutions, such as Fe 2 Cl 3 and chlorine water, 

 a species of magnetic selection apparently occurred. In the experi- 

 ments with Fe 2 Cl 3 solution without chlorine, the magnetised bar was 

 electro-positive ; but when using this reagent combined with chlorine 

 water (see Table C, Col. 4, Divisions I and II), the magnetised bar 

 became electro-negative, possibly owing to the diamagnetic property 

 of the free chlorine influencing its action on the magnetised bar. 

 When, however, the free chlorine had exhausted its direct action on 



