Action of a Magnet on Chemical Action. 43 



Several things are worthy of note in this list. In the first 

 place those solutions of metallic salts which are precipitated by 

 iron all show distinct signs of protective action when the cur- 

 rent is passed through the magnet. Of the various acids "this 

 is not generally true ; only those show the magnetic effect, 

 which act on iron without the evolution of hydrogen ; and are 

 powerful oxidizing agents. In general, substances which acted 

 without the evolution of hydrogen gave an effect with the 

 magnet. 



From these experiments it was quite evident that the protec- 

 tive action, whatever its cause, was more general than, at first 

 appeared and steps were next taken to extend it to the other 

 magnetic metals. Small bars were made of nickel and cobalt 

 and tried in the same manner as before. These metals are 

 acted on but very slightly by most acids, and the range of sub- 

 stances which could be used was therefore very small, but all 

 the substances which gave the magnetic effect with iron poles 

 gave a precisely similar, though much smaller effect, whenever 

 they were capable of acting at all on the nickel and cobalt. 

 This was notably the case with nitric acid, bromine water, 

 chlorine water, and platinum tetrachloride, which were the 

 substances acting most readily on the metals in question. Even 

 with these powerful agents, however, the magnetic action was 

 very much less than with iron, and experimentation on metals 

 even more weakly magnetic was evidently hopeless. 



As a preliminary step toward ascertaining the cause of the 

 magnetic action and its nonappearance where the active sub- 

 stance evolved hydrogen, it now became necessary to discover 

 and if possible eliminate the cause of the reversal of the cur- 

 rent wh\ch regularly followed the protective throw. Experi- 

 ments soon showed that it could not be ascribed to accumula- 

 tion of decomposition products around the electrodes, and 

 polarization, while it could readily neutralize the original de- 

 flection, could not reverse its direction. Whatever the cause, 

 it was one which did not act with any great regularity, and it 

 Was soon found that stirring the liquid while the magnet was 

 on, uniformly produced the effect observed. Since one pole 

 was simply exposed over a small portion of its side while the 

 other had a sharp projecting point, it was the latter which 

 was most freely attacked when there were currents in the 

 liquid, whether these were stirred up artificially or were pro- 

 duced by the change in galvanic action due to the presence of 

 the magnet. When the poles were placed in fine sand satu- 

 rated with acid this reversing action was much diminished, and 

 in fact anything which tended to hinder free circulation of the 

 liquid produced the same effect. Several materials were tried 

 and of these the most successful was an acidulated gelatine 



