564 CHEMISTRY OF THE PROTEIDS CHAP. 



ammonium sulphate solutions, and according to Morner also by sodium 

 sulphate. 



Gelatine and the gelatoses form, as do other albumins, salts with 

 acids and bases ; the salts of gelatoses and gelatin-peptones with HC1 

 have been investigated by Paal. 1 Gelatine is, however, essentially 

 acid in character, for according to Hofmeister, 2 Tatarinoff, 3 and Nasse 4 

 it possesses, when pure, an acid reaction and dissociates carbonates. 

 Hofmeister 2 has analysed the platinum and copper salts of the gelatoses, 

 without, however, obtaining constant values. Nasse 4 has investigated 

 the barium salts, and has found the amount of barium, i.e. the basic 

 equivalent, to rise in passing from gelatin to gelatin-peptones. 

 Halogen-derivatives of gelatine are unknown. 



Gelatine is insoluble in cold water, but swells up in it ; it is also, 

 generally speaking, insoluble in salt-solutions, acids, and alkalies, but 

 is readily converted into a soluble modification, 5 and then differs 

 somewhat from the original gelatine. In hot water gelatine is very 

 readily soluble and, according to the amount of water present, on 

 cooling gives rise either to a nearly solid mass, as employed for 

 carpentering purposes, or to a thin trembling jelly, as used for culinary 

 ends. The temperature for setting and the melting-points of gelatine 

 solutions have been recently reinvestigated by Pauli. 6 Pure gelatine, 

 according to its concentration, sets between 18 and 25, and when 

 heated melts between 26 and 29. The melting and setting tem- 

 peratures are, however, modified by salts and by organic crystalloids. 7 

 Sulphates, citrates, tartrates, acetates, glycerin, and sugar raise the 

 temperature at which gelatine sets, while chlorides, chlorates, nitrates, 

 bromides, iodides, alcohol, and urea diminish the same. Morner 8 has 

 shown that the presence of salts is not essential for the gelatinisation 

 of gelatine, for it sets in the absence of salts. By stronger concentra- 

 tions of salts gelatine is precipitated and gelatinisation is prevented. 8 

 Pauli and Rona have also investigated this question. 



The power of gelatinising is only possessed by unaltered gelatine, 

 but not by its dissociation-products : the gelatoses or glutoses or the 



1 C. Paal, Ber. d. deutsch. cJiem. Ges. 25. 1202 (1892). 

 a F. Hofmeister, ibid. 2. 299 (1878). 



3 P. Tatarinoff, Zentralbl. f. d. med. Wissensch. 1877, p. 275. 



4 0. Nasse, Naturf. GeseUschaft zu Rostock, Rostocker Ztg. 1889, No. 105. 



5 W. S. Sadikoff, Zeitschr. f. physiol. Chem. 39. 411 (1903). 



6 W. Pauli and P. Rona, Hofmeister s Beitr. 2. 1 (1902). Here the former papers 

 of Pauli are abstracted and also the other literature referred to. See also Pascheles 

 (or Pauli), Pfluger's Archiv, 71. 333 (1898). 



7 Levites, Journ. d. russ. phys. chem. Ges. 34. 110 and 439 ; W. S. Sadikoff, 

 Zeitschr. f. physiol. Chem. 39. 396 and 411 ; 41. 15 (1904). 



8 C. T. Morner, ibid. 28. 471 (1899). 



