250 CHEMISTRY OF THE PROTEIDS CHAP. 



FORMALDEHYDE COMPOUNDS 



The action of formaldehyde on albumin was first studied by 

 Trikat 1 in 1892. Blum 2 noticed that the addition of formaldehyde 

 makes albumin non-coagulable, and called the new compound * methyl- 

 ene- albumin.' Benedicenti, 3 Bach, 4 "Weigle, and Merkel, 4 Alsberg 

 and Goldschmith, 5 and Lepierre 5 have investigated these methylene 

 albumins, the fullest account published being that of Schwarz, 5 who 

 worked in Hofmeister's laboratory. He also studied the action of 

 acet-, benz-, and other aldehydes. 



A few drops of formalin (i.e. 40 per cent formaldehyde) added to 

 several cubic centimetres of a solution of crystallised serum-albumin 

 will prevent its coagulation by heat. Part of the formaldehyde dis- 

 appears at once, while another part combines only gradually ; the 

 maximum amount is absorbed after two months, when 43 molecules 

 of aldehyde are taken up for 100 molecules of the albumin-nitrogen. 

 The methylene -albumin does not coagulate on heating ; it is not 

 precipitated by alcohol in the absence of salts, but is precipitated from 

 salt solutions ; it gives most of the albumin-reactions. The ethylene- 

 albumin resulting from acetaldehyde is very soluble in acids and 

 alkalies, but insoluble if the reaction be neutral. It behaves like 

 denaturalised albumin. Methylene-albumin is not precipitated, how- 

 ever, by salts. The higher aldehydes precipitate albumins and have 

 but little action. Concentrated solutions of albumins are converted 

 by formaldehyde into jellies. 



According to Schiff 6 and Schwarz, the aldehyde radical probably 

 combines with the NH 2 -groups, thereby converting the proteid into 

 an acid and simultaneously denaturalising it. Schwarz points out, 

 however, that there are other ways in which aldehyde may act. 

 Special attention is drawn to the observations of Schwarz that 

 halogen -albumins do not unite with formaldehyde, that no albumin- 

 radicals are given off by bringing formaldehyde and albumins together, 

 and that methylene -albumins are digested by pepsin, but not by 

 trypsin * perhaps,' because the trypsin becomes destroyed. 



According to Spiro, 7 albumins combine also with esters, ke tones, 



1 Trikat, Compt. Rend. 114. 1278 (1892). 



2 F. Blum, ibid. 22. 127 (1896). 



8 A. Benedicenti, Arch. f. (Anat. u.) Physiol. 1897, p. 217. 



4 According to Schwarz. 



5 L. Schwarz, Zeitschr.f.physiol. Chem. 31. 460 (1900). (Here the older literature.) 



6 H. Schiff, Liebig's Annalen, 319. 287 (1901). 



7 K. Spiro, Hofmeister's Beitrage, 4. 300 (1903). 



