FROM PROTEID SUBSTANCES. 361 



amounted to full 500 c.c. the clear fluid was jet black in 

 color and absolutely opaque to light. On neutralization of 

 this fluid with dilute acetic acid the melanin was reprecipitated 

 in large dark flocks, leaving a colorless transparent fluid. 

 The pigment was filtered off, washed entirely free from salts 

 with water, and thoroughly extracted with alcohol and ether, 

 after which it was dried to a constant weight at 105 C. 

 When dry the preparation weighed 1.498 grams, equal to 

 practically 5 per cent of the original antialbumid. 

 On analysis this substance gave the following results : 



I. 0.3598 gram substance gave 0.2249 gram H 2 = 6.94 per cent H and 0.7168 



gram C0 2 = 64.26 per cent C. 



II. 0.2044 gram substance gave by the Kjeldahl method 0.02463 gram 

 N = 12.00 per cent N. 



III. 0.2273 gram substance gave 0.02733 gram N = 12.00 per cent N. 



IV. 0.3691 gram substance gave by fusion with NaOH and KN0 8 0.2063 gram 



BaS0 4 = 7.70 per cent S. 



PERCENTAGE COMPOSITION OF THE MELANIN.* 



I. H. HI. IV. Average. 



C 54.26 ... ... ... 64.26 



H 6.94 ... ... ... 6.94 



N ... 12.00 12.00 . . . 12.00 



S ... 7.7 7.70 



A second decomposition, using a larger amount of the same 

 antialbumid 61 grams was now attempted under exactly 

 the same conditions as before, except that the acid mixture 

 was boiled for 110 hours. Fatty acids and free sulphur were 

 detected as before, while the same separation of a black 

 pigment took place. The latter was collected on two filters 

 and the precipitates washed as already described, after which 

 the larger precipitate was dissolved in water containing a 

 little ammonia, the clear filtered solution precipitated by 

 neutralization with 0.2 per cent hydrochloric acid, and the 

 precipitate thoroughly washed with water, alcohol and ether. 



* The ash could not be determined with any accuracy owing to the 

 scarcity of substance, but the small amount of ash left in the platinum tray 

 in the determination of carbon made it quite clear that not more than a small 

 fraction of 1 per cent could be present. 



