No. VII.] APPENDIX. 177 



like a syphon, and at the bottom a piece of tow was thrust, in order that a 

 separation might so far be effected, that the solution on one side could not 

 readily pass to the solution on the other. Having thus completed the 

 arrangement, a galvanic circuit was passed through the fluid ; when at the 

 cathode, hydrogen was evolved, and at the anode no oxygen, on the con- 

 trary, was given off, but the solution became of a dark colour. The dark 

 solution was found to precipitate only the protosalts of iron, and on 

 evaporation deposited red crystals of the ferrosesquicyanuret, but at the 

 cathode potash was discovered. The rationale of this change may be 

 deduced from, circumstances attending slight alterations of arrangement : 

 for if on the zinc side of the bent tube a saturated solution of the ferro- 

 cyanate be placed, and on the platinum side distilled water, and then the 

 galvanic circuit be completed, potash will appear at the platinode, and red 

 ferrocyanate at the zincode. On the contrary, if the distilled water is 

 placed at the zinc side and the ferrocyanate at the platinum side, potash is 

 left at the platinode, whilst at the zincode no red ferrocyanate is found, 

 but a substance which does not redden litmus-paper, and which speedily 

 decomposes into Prussian blue : this is probably ferrocyanogen. Thus it 

 appears that one equivalent of the yellow ferrocyanate is decomposed, the 

 free potash travelling one way and the hydrof errocyanic acid the other ; 

 the oxygen unites with the hydrogen of the acid and sets ferrocyanogen at 

 liberty ; this again unites with an equivalent of f errocyanuret of potassium 

 to form the ferrosesquicyanuret. 



Various other attempts were made to form the red ferrocyanate 

 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 

 was 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 etherial solution 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 precipitate the persalts of iron. This change takes place 

 with a rapidity exactly proportionate to the wasting of the phosphorus ; 

 for if the temperature is below 45, 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 precipitate is produced of phosphate of iron ; but after it 

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



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