358 THE FORMATION OF MELANINS 



less closely with the earlier data obtained by Kiihne and Chit- 

 tenden.* Also noticeable is the somewhat larger percentage 

 of sulphur present in antialbumid. A large amount of this 

 sulphur exists loosely combined in the antialbumid molecule, 

 and the question at once arises whether this loosely combined 

 sulphur can be driven off by continued hydrolysis with dilute 

 sulphuric acid. This point was tested by taking a portion 

 of the antialbumid prepared as above and heating it further 

 with 3 per cent sulphuric acid. After exposure at 100 C. 

 in the sterilizer for 6 hours the acid fluid was found to yield 

 a strong reaction for loosely combined sulphur, while the 

 residue of antialbumid gave an equally marked reaction for 

 loosely combined sulphur. The acid fluid was therefore 

 filtered off, the antialbumid washed with water, and again 

 heated for some hours with fresh 3 per cent sulphuric acid. 

 This process was repeated until the aggregate period of heat- 

 ing had reached 38 hours, at the end of which time the last 

 acid fluid was found free from loosely combined sulphur. 

 The antialbumid remaining, however, still gave a striking 

 reaction for sulphur with potassium hydroxide and plumbic 

 acetate, thus showing that the loosely combined sulphur con- 

 tained in the antialbumid molecule cannot be removed entirely 

 by this method of hydrolysis. Especially noteworthy was 

 the continued shrinkage of the antialbumid during this long 

 process of heating with the dilute acid, until at the termina- 

 tion of the treatment the substance was greatly diminished in 

 bulk, a fact which accords with .Schutzenberger's f original 

 observations that this substance, when heated continuously 

 with dilute acid, slowly but progressively disappears. Some- 

 what noticeable, however, is the fact that such portion of the 

 antialbumid as does resist this long continued action of the 

 dilute sulphuric acid is not widely different in composition 

 from the original antialbumid. Thus, analysis of the product 

 remaining after the 38 hours' heating gave the following 

 results : 



* Kiihne and Chittenden, Zeitschrift fur Biologic, 1883, xix, p. 176. 

 t Schtitzenberger, Bulletin de la socie'te chimique de Paris, 1875, xxiii, 

 p. 161. 



