TYOCYANINE. 165 



chloride must be digested with dilute hydrochloric acid, 

 filtered, and the filtrate carefully neutralised Yvdth 

 soda. A precipitate of pyine will appear (q.v.). 



6. Distil fresh pus carefully with dilute phosphoric 

 acid. To the distillate add some sodium carbonate to 

 very slight alkaline reaction, evaporate down and test 

 for volatile acids (q.v.). 



7. Evaporate pus to dryness at 100 C. and burn. 

 Examine the ask. 



Pyine. 1. Obtain from pus by the method 

 described under Pus, 5. 



2. Dissolve in dilute caustic potash, and add acetic 

 acid : a precipitate will appear, insoluble in excess of the 

 acid. 



3. To the solution in potash add hydrochloric acid: 

 a precipitate soluble in excess will be produced. 



4. To the solution in dilute hydrochloric acid add 

 potassium ferrocyanide : no precipitate. 



5. Treat with nitric acid : it will turn yellow and 

 dissolve. 



6. To a solution in very dilute nitric acid add lead 

 acetate or mercuric chloride : a white precipitate will 

 fall. 



7. Dissolve in weak hydrochloric acid or caustic 

 potash and boil: no precipitate will ensue. 



Pyocyanine. 1. Linen stained with "blue pus" 

 must be extracted with cold water containing a little 

 ammonia, and the evaporated and filtered extract 

 digested with chloroform. Shake the chloroform 



