1888.] Electro-chemical Effects on Magnetising Iron. 155 



experiments with bromine, HN0 3 , and the copper salts, affords 

 sufficient indication that the liability to error from temperature 

 causes was slight. To demonstrate that the magneto- chemical effect 

 was not in these observations due to variation of temperature conse- 

 quent on possible heating of the coil, a further set of experiments 

 (Table C, Cols. 10 and 11, Divisions II) was made with solutions of 

 ferrous sulphate and also of ferric chloride in another form of 

 apparatus, wherein the unmagnetised bar B was surrounded by a 

 slightly higher temperature (about 5° to 10° F.) during the observa- 

 tions than the magnetised bar A. This was accomplished by surround- 

 ing the limb of the U -tube containing the bar B, during the observa- 

 tion, with a specially constructed water-bath containing water at a 

 temperature of about 5° to 10° F. above the temperature of the 

 solution in the coil tube A, the difference of temperature was ascer- 

 tained by small thermometers respectively placed in limbs A and B of 

 the (J'* u ^ e ' another thermometer being in the water-bath. The 

 magnetised bar was, however, able to maintain its positive position, 

 notwithstanding the higher temperature around the unmagnetised 

 one. The present memoir contains the results of many repeated 

 experiments, each record in the tables being the average of a 

 considerable number of observations. In Parts I and II a total of 

 about 592 iron and steel bars have been experimented upon, 346 bars 

 being required for the experiments of Part II. 



Explanation of Results on Table C. 



Hydrochloric Acid, cone, sp. gr. 1*16, Col. 1. — No perceptible 

 electro-chemical effect was obtainable with this reagent. 



Bromine and Potassium Bromide, Col. 2, Divisions I, II, and III — 

 It was found that pure bromine for various reasons was too powerful a 

 reagent to use in these experiments ; a strong solution was therefore 

 prepared of the following composition. Bromine, 1066 - 4 grains, potas- 

 sium bromide, 520 grains, and 3| ozs. of water. This solution was 

 very energetic in its action on the metals, and considerable care was 

 required in conducting the experiments therewith ; but with due pre- 

 cautions admirable results were obtained. The magneto-chemical 

 effect was very great with this reagent, the E.M.F. between the mag- 

 netised and unmagnetised bars sometimes reaching as high as 

 one-twentieth of a volt. The highest E.M.F. appeared to be manifested 

 at or near the time of the energetic effervescing attack on the metal ; 

 though the E.M.F. between the bars was always considerable from 

 the earliest commencement of the magnetisation of bar A in the coil. 

 Experiments were made on both wrought-iron and steel bars. The 

 experiments, Col. 3, Divisions I and II, were made with a much 

 weaker bromine solution, though of similar general composition. 



