ACTION OF A MAGNET ON CHEMICAL ACTION 



245 



promptly discharged itself when the charging was discontinued by 

 breaking the current through the magnet. The gradual reversal of 

 the current some little time after exciting the magnet was noted fre- 

 quently in these cases, as before. Owing to this peculiarity and their 

 generally very irregular action, the various salts were disagreeable sub- 

 stances to experiment with, though as a rule they gave positive results. 



Unless the poles were kept clean experimenting became difficult from 

 the accumulation of decomposition products about them and oxidation 

 of their surfaces. A few experiments showed how easily the original 

 deflection could be modified, nearly annulled or even reversed in direc- 

 tion by slight differences in the condition of the poles. These difficul- 

 ties of the method are, however, more than counterbalanced by its 

 rapidity and delicacy when proper precautions are taken. 



Xearly thirty substances were tested in the manner previously de- 

 scribed; but comparatively few of them gave very decided effects with 

 the magnet, though, as later experiments have shown, the protective 

 action is a general one. The substances first tried were as follows. 

 The table shows the various acids and salts tried, and their effects as 

 shown by the original apparatus: 



Substances. 



Effect due to 

 Magnet. 



Notes. 



Nitric acid 



Sulphuric " 



Hydrochloric acid. 



Acetic 



Formic 



Oxalic 



Tartaric 



Chromic 



Perchloric 



Chloric 



Bromic 



Phosphoric 



Permanganic 



Chlorine water 



Bromine (l 



Iodine " 



Copper sulphate 



" nitrate 



" acetate 



" chloride 



" tartrate 



Mercuric bromide 



" chloride 



Mercurous nitrate 



Ferric chloride 



Silver nitrate 



Platinum tetrachloride. 



Strong. 



Little or none. 

 n 



None. 



Some effect. 

 K 



None. 



Slight effect. 

 Decided " 



Some. 



Slight. 

 Some. 



Decided. 

 Some. 



Always powerful protective throw. 

 Does not act very readily on the iron. 



Sometimes quite distinct throw, irregular. 

 Much less marked than with chromic. 



Hardly any effect on iron. 

 More than with perchloric. 



Mainly showing as throw, on breaking. 



Throw, on breaking. 



Very slight solution, weak. 



Mainly as throw on breaking, [breaking. 



Both protective throw, and sometimes on 



Action very irregular. 



