Behaviour of Chemical Compounds. 279 



before the transformation. Therefore the change of colour 

 cannot arise from a possible separation of colloid oxide of 

 chromium from the salt, which, like the colloid oxide of iron, 

 would exhibit a lower degree of magnetism than the oxide 

 combined with the acid. 



16. JIagnetism of the Cyanides of the Magnetic Metals. — The 

 precipitates obtained in the flask of the torsion-apparatus by 

 adding hydrocyanic acid to the salts of acetic acid, of cyanide 

 of nickel and cyanide of cobalt, possess a much lower magne- 

 tism than the corresponding oxygen and haloid salts. If the 

 former be denoted by ficy, the latter by [jl^, then with 



Cyanide of cobalt yLtf_y — 0'60-0'65/^s, 



Cyanide of nickel //-ei/ = 0*45///s. 



When the precipitates are dried, the molecular magnetism of 

 the cobalt cyanide remains nearly constant, that of the nickel 

 cyanide rises to about O'GSyLt^. 



While the simple cyanides of the magnetic metals still show 

 a not inconsiderable amount of magnetism, this diminishes to 

 a great extent or quite vanishes when those metals enter into 

 combination with cyanogen in other atomic groupings. Thus, 

 as Faraday showed, ferricyanide of potassium is only feebly 

 magnetic, and ferrocyanide of potassium is even feebly dia- 

 magnetic, although the latter salt contains more iron in its 

 molecule than the former. Correspondingly, also, in these 

 salts the iron cannot be directly demonstrated by the ordinary 

 reagents. 



The mangani- and cobalticyanides of potassium behave 

 altogether similarly to the ferricyanide. According to former 

 experiments the molecular magnetism of these salts, as well in 

 solution as in the solid state, is the following: — 



Dissolved. Solid. 



Manganicyanide of potassium . 30*5 31*9 



Ferricyanide of potassium . . 16*1 15*7 



Cobalticyanide of potassium — 0*75 



Here also the molecular magnetism of the iron-salt is the 

 mean between those of the manganese- and the cobalt-salt. 

 In comparison with the magnetism of the protoxide salts it 

 appears diminished in an approximately equal proportion: — 



100-4-31-2 = 69-2; 83-l-15-9 = 67-2 ; 67-2 + 0-75 = 68. 



The behaviour is therefore the same as if to the magnetic ra- 

 dicals a strongly diamagnetic radical, with the diamagnetism 

 belonging to it, were added. 



A further insight into the constitution of the ferro- and 



