290 On tlie Magnetic Behaviour of Chemical Comjoounds. 



oxide, as well as for a very acid solution of ferric chloride, 

 the increase of dissociation with a rising temperature can also 

 be directly determined by observation of the magnetism of 

 neutral and other iron-solutions at different temperatures. 

 But these experiments, like all the other magnetic observa- 

 tions on dissociation, present the difficulty that very precise 

 observations are needed in order to obtain accurate results, 

 since small errors in the determination of the magnetism have 

 a great effect. On this, too, I reserve to myself a further 

 communication. 



If with the solution of a ferric salt that of another salt, of a 

 different acid, be mixed, a partial exchange of the constituents 

 of the two salts takes place. If the dissociation undergone 

 by the newly formed iron-salt in the solution be different from 

 that of the first employed, we can, from the alteration of the 

 magnetism belonging to the unit weight of iron in the solu- 

 tion, first calculate the quantity of ferric oxide newly disso- 

 ciated. In this way solutions of various sulphates were 

 mixed with a solution of ferric chloride, which with not too 

 great a dilution is scarcely dissociated. In the accompanying- 

 Table, under 7n is given the magnetism of the unit weight of 

 iron in the mixture in percentages of that of the iron in non- 

 dissociated iron-salts, under cV the percentage amount of the 

 dissociated ferric oxide: — 



1 eq. ferric chloride T\dth eq[. m. x. 



Sulphate of soda ^ 89*3 13-7 



„ „ i 82-9 21-9 



„ „ 2 78-7 27-3 



Sulphate of magnesia \ 91*6 108 



„ „ 1 85-8 18*2 



„ „ 2 83-7 20-9 



Zincic sulphate i 88*3 15*0 



„ „ 1 85-3 18-8 



„ „ 2 81-4 23-8 



Cupric sulphate \ 93*4 8-5 



„ „ i 89-2 13-8 



„ „ 2 84-7 19-6 



Cobaltous sulphate ^ 95*6 5*6 



., „ i 88-0 15-4 



Nickelous sulphate h 92-1 5*0 



„ „ i 86-8 16-9 



If we might assume that the ferric chloride which is not 

 converted into ferric sulphate, even after the mixing is still 

 contained undecomposed in the solution now poorer in ferric 

 chloride, and that the ferric sulphate formed has, to the amount 



