360 THE FORMATION OF MELANINS 



With a view to the possible preparation of a melanin, 30 

 grams of pure dry antialbumid (the first sample analyzed) 

 were placed in a flask with 300 c.c. of 10 per cent sulphuric 

 acid, the flask connected with an inverted Liebig's condenser, 

 and the mixture boiled directly over a flame for 79 hours. 

 When first heated, the acid was almost colorless, but as 

 decomposition progressed the color changed first to purple 

 and finally to jet black. Early in the course of the heating a 

 light film, shown later to be composed of fatty acids, was 

 deposited on the sides of the condenser, and the odor of 

 volatile fatty acids was very distinct.* As the boiling pro- 

 gressed, bright yellow crystals hi rosettes were seen, both 

 within the condenser and clinging to the neck and sides of 

 the flask. These crystals were eventually collected and 

 tested. They burned with a blue flame, forming acid fumes ; 

 they were insoluble hi water, alcohol, and ether, but rapidly 

 soluble in carbon disulphide. From the latter fluid they 

 recrystallized in the characteristic rhombic octahedra of native 

 sulphur. 



At the conclusion of the 79 hours of heating, and after the 

 acid fluid had cooled, the mixture was filtered through paper, 

 leaving a residue of black amorphous matter, while the clear 

 filtrate was quite black in color. Obviously, the fluid con- 

 tained considerable black pigment in solution, but owing to 

 the large admixture of leucin, tyrosin, and other substances 

 present, attempts to isolate the pure pigment from the solution 

 were not very successful. Attention was therefore directed 

 to the insoluble pigment on the filter paper. This was washed 

 with water until free from acid, and then with alcohol and 

 ether, in all of which it was insoluble. As the pigment was 

 found to be extremely soluble in weak alkalies, the precipitate 

 was treated with a very little 0.2 per cent potassium hydroxide 

 solution, in which it quickly dissolved, leaving a small slate- 

 colored residue (too small to identify) which was readily 

 washed free from the melanin-like substance. Although the 

 volume of the weak alkaline fluid with the washings now 

 See R. Cohn, Zeitschr. f. physiol. Chem., 1896, xxii, p. 158. 



