342 CHEMISTRY OF THE PROTEIDS CHAP. 



the acid stains." Albumin fixed in acetic acid alcohol combines at once 

 with the acid dyes in neutral solutions, probably because the acetic 

 acid radical, which had united with the albumin-molecule at the time 

 of fixation, becomes now replaced by the colour-acid of the staining 

 fluid (Mann). 1 



It is of great interest that alcohol is able to preserve the pseudo- 

 acid pseudo-basic nature of the amphoteric albumin-molecule. See 

 remarks of the author on p. 219. 



0. v. Fiirth 2 has noticed that different, alcohol-coagulated albumins 

 become denaturalised with different rapidities ; thus myosin (paramyo- 

 sinogen of Halliburton) and ovalbumin are denaturalised more quickly 

 than are myogen (myosinogen of Halliburton) and serum-albumin. 



St. Hilaire 3 has further pointed out that nucleo-histones are 

 decomposed by alcohol. 4 



Aceton behaves similarly to alcohol (Mann, 5 Spiro). The 

 coagulum is at first soluble, but then becomes denaturalised 

 secondarily. 



Alkaloidal Reagents and Dyes. When precipitated with 

 phosphotungstic acid or with aniline dyes according to the methods 

 of Mathews and Heidenhain (see p. 225), albumin remains for a time 

 soluble, but ultimately becomes coagulated (Cohnheim). 



Salts of Heavy Metals. Whether precipitation with the salts- 

 of the heavy metals produces denaturalisation at once is not known, 

 but that denaturalisation supervenes later has been shown by Billow ^ 

 and Werigo. 7 (See pp. 303-315.) 



Silver Oxide. Schadee van der Does 8 has described how solu- 

 tions of egg- and serum-albumin may be rendered uncoagulable by 

 being shaken up with freshly prepared metallic silver, or freshly pre- 

 pared or not too old silver oxide. Silver chloride and silver sulphide 

 do not act in this way. It is suggested by him that the silver may 

 possibly replace the sulphur of the albumin-molecule. The author 9 

 suggests that silver in the metallic state, especially when in fine sub- 

 division, being slightly oxidised, must act in the same way as does the 



1 Mann, Physiological Histology, 1902, p. 351. 



2 0. v. Fiirth, Arch.f. experiment. PathoL u. Pharmakol. 36. 231 (1895). 



3 Constantin Saiiit-Hilaire, Zeitschr. f. physiol. Chem. 26. 102 (1898). 



4 See Mann's Physiological Histology, p. 320. 



5 Mann, ibid. 1902, pp. 88, 104. 



6 K. Billow, Pfliiger'.s Arch. f. d. gesammte Physiol. 58. 207 (1894). 



7 B. Werigo, ibid. 48. 127 (1891). 



8 Schadee van der Does, Zeitschr. f. physiol. Chem. 24. 351 (1897) ; also F. Bayer 

 and Co., ' Patentschrift,' Chem. Zentralblatt, 1900, I. 524, and 1901, I. 652. 



9 Mann, Physiological Histology, 1902, p. 67. 



