70 THE GELATIN FROM WHITE 



of gelatination is not to be ascribed to extensive conversion 

 into gelatoses, but is more probably connected with the greater 

 purity of the products. Thus O. Nasse * observed that the 

 more nearly free from ash his gelatin was, the less the tendency 

 to gelatinize, diminution in the percentage of ash leading to 

 loss of the power of gelatination. This being the case, freedom 

 from inorganic constituents might naturally be expected to 

 result in greater solubility in cold water. Hammarsten f 

 mentions the well-known fact that gelatin is more easily 

 precipitated by alcohol in the presence of neutral salts, and he 

 further mentions that " it is precipitated by tannic acid in the 

 presence of salt." Salts unquestionably do exert a very 

 marked influence in rendering precipitation of gelatin more 

 complete, from which it might be argued that their absence 

 from or diminution in gelatin would enhance its solubility in 

 water and decrease its power of gelatinizing. On the other 

 hand, it is of course possible that the long-continued process 

 of preparation may have resulted in the formation of some 

 gelatose, although great care was exercised to avoid such an 

 occurrence, the heating with water in the conversion of 

 collagen into gelatin having been of comparatively short 

 duration. 



In the precipitation of pure gelatin with most reagents 

 there is noticeable a tendency toward incompleteness of 

 separation and a dependence of the reaction upon the attendant 

 conditions, especially the concentration of the fluid. Upon 

 this fact, no doubt, many of the conflicting statements in 

 regard to the reactions of gelatin depend, although some of 

 the differences noted by various writers are due to the lack of 

 purity of the gelatin employed, and possibly also to the 

 source from which it was derived. Further, the fact that with 

 certain reagents only slight precipitates are obtained has led 

 to the belief that these reactions are due to the presence of 

 albumin and not to gelatin itself, whereas the correct explana- 

 tion in many cases is to be found in the solubility of the 



* Jahresbericht d. Thierchemie, 1889, p. 31. 

 t Lehrbuch d. physiol. Chem., 1895, p. 47. 



