PRODIGIOSIN PIGMENTS. 67 



several pigments, present great variation. (See Schneider, 

 A. K. i, 201, regarding spectra and peculiarities.) They 

 are, however, closely related to the widely distributed lipo- 

 chromes (pigment substances of fats, yolk of egg, etc. ) and 

 the carotin of yellow carrots. (Compare Leisenberg and 

 Zopf, C. B. xn, 659.) 



(6) Prodigiosin pigments. By prodigiosin I designate 

 the beautiful pigment of the Bact. prodigiosum and its 

 nearest relatives. It is soluble in ether as yellowish- 

 brown and in alcohol as garnet-red. It is turned yellow 

 by alkalis, violet-red by acids, and brownish-red by con- 

 centrated sulphuric acid. Zinc and hydrochloric acid re- 

 duce the pigment to a colorless leuko-product. The spec- 

 troscopic behavior is very characteristic. 



Violet pigments. In connection with the bacterium 

 violaceum, and also the Bacterium janthinum, there is pro- 

 duced, according to Schneider (verified by myself), a violet 

 pigment (janthin) which is insoluble in water, readily 

 soluble in alcohol, but insoluble in ether, benzol, and chloro- 

 form. If dry, it becomes yellow when treated with con- 

 centrated sulphuric acid and emerald-green when treated 

 with caustic potash. In alcoholic solution all strong acids 

 and ammonia produce a green or bluish-green color. With 

 zinc and sulphuric acid the color is destroyed (Schneider, 

 I c.). 



The beautiful blue pigment of the Bact. indigonaceum 

 Claessen was very incompletely examined by Claessen and 

 Schneider (L c.). This pigment is not dissolved by ordi- 

 nary solvents. Hydrochloric acid gives a transitory blue, 

 turning to a yellowish-brown solution. Also, other acids 

 in dissolving it cause its decomposition. Caustic potash 

 turns the color bluish-green. I am unable to add any- 

 thing further. 



Different from these is the blue pigment produced by 

 the Bacterium syncyaneum (blue milk), which I propose 

 to call syncyanin. It is also entirely independent of the 

 bacterio-fluorescein forms (see below). This pigment was 

 pointed out by Thumm as very unstable ; acids turn it 

 steel-blue, in weaker acids it is blue-black, neutral it is 

 black, alkaline it is brownish-black. For details see the 

 special part. 



