in SEPARATION OF BACTERIAL PIGMENTS 149 



(6) Bacillus prodigiosus. 



(1) Prepare twenty potato or agar-agar streak cultures 

 of the Bacillus prodigiosus, which must be kept at 22 C., 

 till the dark red pigment has been formed copiously. 



(2) To each tube add 5 to 10 cc. of pure ether and shake 

 vigorously, till all the red pigment has been dissolved out. 



(3) Collect the ethereal extracts and pour them into a 

 separating funnel : the red ethereal extract will rise to the 

 surface. 



(4) Allow it to stand in the dark for twenty-four hours, 

 and then separate the coloured ethereal extract. 



(5) Filter this, if necessary, through paper moistened 

 with ether. 



A clear red solution is thus obtained, which may be 

 concentrated by slow evaporation in the dark at 

 38-5 C. 



Reactions 



(1) Evaporate a little in a porcelain dish at 38*5 C. : a 

 crystalline residue is obtained. 



(2) Add a few drops of hydrochloric acid : no change 

 in colour. 



(3) Add a few drops of caustic soda or caustic potash : 

 the red colour is discharged on shaking, the upper or 

 ethereal layer turning yellow. 



Now add, drop by drop, hydrochloric acid : the red 

 colour will gradually reappear in the upper ethereal 

 layer. 



(4) Allow the ethereal red extract to stand in the 

 light : the red colour disappears. 



