8 Biography of Berzelius. 



or silver, correspond so completely with the analogous chlo- 

 rine compounds, he was of opinion that if he could by this 

 investigation detect oxygen in the ferrocyanic compounds, it 

 would be a strong proof of its presence in muriates likewise, 

 and, consequently, evidence in favour of the old theory of the 

 nature of chlorine. 



However, the result of these investigations was the oppo- 

 site of that which he expected, and thus the main argument 

 against the new doctrine of the nature of chlorine fell to the 

 ground. When gradually other reasons for the greater pro- 

 bability of the new theory were discovered, Berzelius adopted 

 it with the most amiable candour, and relinquished the old 

 theory which he had so long and so ably defended. 



One, among other, of these reasons was, as I know, the fol- 

 lowing : — Immediately after Berzelius' investigations on the 

 cyanides of iron, Leopold Gmelin obtained the interesting red 

 double salt of cyanide of potassium and cyanide of iron, which 

 is anhydrous and contains no oxygen. The red colour of the 

 peroxide of iron, which is more or less communicated to all 

 its salts except the neutral ones, was to Berzelius an addi- 

 tional reason for regarding the red perchloride of iron as an 

 actual salt with an oxygenous base ; and, as in the salt 

 obtained by Gmelin. notwithstanding its red colour, the iron 

 was not in the state of oxide, but directly combined with 

 cyanogen, one double atom of iron with three double atoms 

 of cyanogen, Berzelius saw that it was probable that the red 

 colour of iron compounds was not owing alone to the pre- 

 sence in them of peroxide, but was also common to those in 

 which one double atom of iron is combined with three double 

 atoms of chlorine or cyanogen. 



Another main inducement to adopt the new theory of the 

 nature of chlorine, consisted in the results which he derived 

 in favour of it from his subsequent comprehensive researches 

 upon alkaline sulphurets. According to Berthollet's inves- 

 tigations, these bodies were regarded as combinations of sul- 

 phur with alkalies until Vauquelin put forward the opinion, 

 that when a fixed alkali was melted with sulphur, a part of 

 the alkali was reduced to the metallic state, sulphuric acid 

 was formed, and a mixture of alkaline sulphate and sulphu- 



