Mr. Smee on the Ferrosesqnicyanurct of Potassium. 197 



Various other attempts were made to form the red ferro- 

 cyanate by oxygen, such as heating it with nitrate of potassa, 

 but the mixture exploded at a temperature below redness. 



When a mixture of powdered ferrocyanate and peroxide 

 of manganese were heated together no ferrosesquicyanuret 

 was formed. Several other oxides, as those of mercury, silver, 

 tin, iron, &c. &c, were digested with ferrocyanate of potassa, 

 but none that were tried, except the peroxide of manganese, 

 formed the red ferrocyanate ; many of them were converted 

 into cyanurets. 



A current of oxygen gas passed through the solution of 

 the salt produces no alteration, showing that the gas must be 

 in a nascent state to cause the change. 



The next substance we have to examine is phosphorus, 

 and its action is somewhat remarkable ; for little or no change 

 is effected by the addition of an alcoholic or aetherial solu- 

 tion of phosphorus. When a piece of phosphorus is also 

 placed in a solution of the ferrocyanate, or when phosphorus 

 is heated with powdered ferrocyanate, the sesquicyanuret 

 is not produced ; but if a stick of phosphorus is placed in a 

 bottle containing a solution of the salt, and only a portion of 

 it is covered with the liquor, the phosphorus gradually burns 

 away, the solution becomes sour and red, and ceases to preci- 

 pitate the persalts of iron. This change takes place with a 

 rapidity exactly proportionate to the wasting of the phospho- 

 rus ; for if the temperature is below 4-5°, but little action takes 

 place, but above 60° the reddening is very speedily produced. 

 The red solution is not to be tested with the salt of iron 

 whilst it is acid, for in that case a copious greenish-white pre- 

 cipitate is produced of phosphate of iron ; but after it has been 

 neutralized with potassa a solution of baryta is to be added, 

 to throw down the phosphate, and a drop of dilute sulphuric 

 acid may then be added to remove any excess of baryta. 



The solution will now be found not to precipitate persalts 

 of iron, but, on the contrary, a large quantity of Prussian blue 

 is produced with the protosalts. The actual combustion of 

 the phosphorus seems essential to this change ; for if the water 

 in which phosphorus has been allowed to burn, be added to 

 the solution of the ferrocyanate, a similar change will not be 

 produced. The cause of this change appears paradoxical, 

 for phosphorus has in other instances a deoxidizing agency, 

 so that a piece placed in a solution of either gold, silver, pla- 

 tinum, or copper, has the metal precipitated upon it. Per- 

 haps it depends upon decomposition of water and the forma- 

 tion of phosphuretted hydrogen ; for a narrow bottle, to which 

 air has but limited access, is more favourable to the change 



