18 KANSAS ACADEMY OF SCIENCE. 



edge of the causes of the variation in the temperature of transition gained from 

 the preliminary experiments, to obtain entirely concordant results, but we suc- 

 ceeded nevertheless in establishing a number of interesting facts concerning the 

 action of the magnet. The following paragraphs descriptive of the more interest- 

 ing results obtained with the magnet are taken directly from the rough notes made 

 while the investigation was in progress. 



(a) 8cc. HNO3 sp.gr. 1.368 acting upon 1 grain of iron in the magnetic field. 

 The tube containing the iron and acid was immersed in water which up to the be- 

 ginning of the experiment had been boiling, but from which the flame had just been 

 removed. The strength of the field, which was insufiicient to destroy passivity at 

 the temperature of the room (20°), was not measured. EfiFervescence began at once, 

 and increased until the thermometer indicated 51°, when the explosion characteristic 

 of the loss of passivity occurred, blowing most of the liquid from the tube. The 

 remainder became quiescent again, but when touched with the thermometer bulb 

 its explosive activity returned. The reaction differed apparently in its nature from 

 that taking place out of the field. The products of the reaction, when poured from 

 the tube, left the tube and the thermometer bulb clean, whereas after the ordinary 

 reaction they were thickly coated with a black residue which could not be washed off 

 and the complete removal of which necessitated long boiling in acid. 



(6) A repetition of experiment (a), with the magnet not acting. The thermom- 

 eter rose steadily to 89°, when the transition to the active state took place. 



(c) Conditions those of experiment (a). Temperature of transition again 51°. 

 We noticed that passivity was not lost throughout the mass of iron at once, but 

 began at a single point on the side of the tube, whence streams of gas were evolved, 

 while the rest of the iron remained passive. 



From this as a center the action spread until the entire mass became involved. 

 The temperature noted was that at which activity had become general. 



(d) Conditions those of experiment (a), excepting that the magnet was inactive 

 until the temperature of the solution reached 60°, when the circuit was closed. Pas- 

 sivity was destroyed at once. 



(e) Conditions those of experiment (a), excepting that the circuit was made and 

 broken at every degree from 40° upward by tapping a key. But little effect could 

 be noticed until in the neighborhood of 60°. Each tap was followed by momentary 

 effervescence and by a sudden rise of the thermometer, which were more and more 

 marked as the solution became hotter. . Complete and permanent activity, such, 

 namely, as was capable of maintaining itself without the continued action of the 

 magnet, did not occur until a temperature of 87.5° was reached. 



(/) A repetition of experiment (a), but with less current, [.28, as much as in- 

 dicated by a tangent galvanometer in the circuit.] The magnet was in function 

 throughout the experiment. The transition temperature was 84.5°. 



(f/) The acid and iron were placed in a bath at 20°, and brought into a much 

 stronger field than that employed in experiment (a). ( Strength of field, estimated 

 by the method described in a former paragraph, was about 20,000 H.] Loss of pas- 

 sivity in this field occurred instantly upon closing the circuit. 



{h) The acid was diluted with one-half its bulk of water; and the iron having been 

 introduced under the protection of a strip of platinum foil remained passive when 

 the latter was withdrawn. The temperature of the acid was 23°. The iron lost its 

 passivity instantly in a field of very moderate intensity, and regained it only when 

 removed from the neighborhood of the magnet. The very slight residual magnetism 

 of the electro-magnet was found to be sufficient to destroy jjassivity in this dilute 

 acid, the action recurring violently whenever the tube was brought between the poles 



