OVOMUCOID 49 



in 70 per cent alcohol and this solution is evaporated under re- 

 duced pressure, with the occasional addition of absolute alcohol, 

 until a thick syrup is again obtained. The gliadin is precipitated 

 from this syrup by the method just described, washed three times 

 with ether (distilled over sodium), partially dried over sulphuric 

 acid, ground up as finely as possible, and then completely dried 

 over sulphuric acid, in partial vacuum, at room temperature. 

 The conditions of the precipitation, of course, involve contami- 

 nation with NaCl. According to Osborne (21) there is only one 

 alcohol-soluble protein in flour; on standing in alcoholic solution, 

 however, a protein insoluble in alcohol or alcohol-water mixtures 

 is precipitated within a few hours. Kosutany (13) believes that 

 this substance is derived from gliadin by the splitting off of water 

 and is identical with glutenin, the alcohol-insoluble and water- 

 insoluble protein constituent of gluten. According to Osborne 

 (21), however, glutenin differs qualitatively from gliadin in that, 

 upon hydrolysis with hydrochloric acid, glutenin yields glycocoll 

 and lysin, while gliadin yields neither of these amino-acids. 



10. Ovomucoid. — The following method of preparing ovo- 

 mucoid is a modification of that originally employed by Morner 

 (17) (33) (36). 



The whites of eggs are beaten up to a froth and allowed to 

 stand in shallow vessels over night. The subnatant fluid is then 

 poured off, the froth being rejected. This fluid is diluted to five 

 times its volume with distilled water, and to every litre of the 

 diluted fluid is added 130 cc. of approximately A^/10 acetic acid 

 (made up by diluting 10 cc. of glacial acetic acid to 1750 cc). 

 This mixture is heated slowly to boiling point, being rapidly 

 and uniformly stirred meanwhile, and after being allowed to boil 

 for about 3 to 5 minutes, is put aside in rather shallow vessels 

 for about 12 hours. At the end of this time most of the coagulum 

 has floated to the top and the clear pale yellow subnatant fluid is 

 filtered through hardened filter paper. Filtration is very rapid, 

 and the filtered fluid, when boiled, either with or without further 

 addition of acetic acid, remains perfectly clear. The fluid which 

 is thus obtained is now slowly evaporated to one-fifth of its volume, 

 the temperature of the fluid never being allowed to rise above 

 55° C. After allowing this fluid to cool, the protein is precipitated 

 from it by the addition of ten volumes of 99.8 per cent alcohol 

 and is allowed to settle in tall glass cylinders. The supernatant 



