70 BEHAVIOUR OF IRON SALTS, IN THE PRESENCE OF 



acid the blue colour was deeper than with hydrogen peroxide. 

 When a decolourized solution was allowed to stand for twenty- 

 four hours, the jelly, which formed on cooling, was found to 

 be deep blue at the surface. The blue colour gradually 

 decreased until, at a depth of three inches, the jelly was 

 colourless. 



(e) Experiments luith fenrous salts. 

 Dilute solutions of ammonium ferrous sulphate and 

 potassium feiTocyanide were separately mixed with varying 

 quantities of the white of egg solution, and allowed to stand 

 some minutes. On adding ammonia or sodium hydroxide to 

 the ferrous ammonium sulphate mixtures ferrous hydroxide 

 was invariably precipitated. When the concentration of the 

 white of egg was relatively large, the ferrous hydroxide pre- 

 cipitated somewhat slowly. The potassium ferrocyanide 

 mixtures were tested with solutions of iron alum and copper 

 sulphate. On the addition of a few drops of the alum solution 

 to the mixture a deep blue precipitate was always proauced, 

 while with the copper sulphate solution a brick red precipitate 

 of copper ferrocyanide was immediately formed. The same 

 results were obtained when gelatine was used instead of white 

 of egg. 



(f) Exp&riments ivith other organic suhstances. 

 Dilute solutions of all the iron salt previously used were 

 separately mixed with varying quantities of cane sugar, of 

 tartaric acid, and of glycerine. The mixtures containing 

 soluble Prussian blue were kept at 60° for an hour, while the 

 others were allowed to stand at room temperature for some 

 minutes. Apart from the prevention of the precipitation of 

 ferric hydroxide on the addition of ammonia or sodium 

 hydroxide to the mixtures containing ferric chloride, it was 

 found that neither sugar, tartaric acid, nor glycerine apparently 

 hindered the different iron salts from reacting with the various 

 reagents previously used for their denomstration. 



