48 CHEMICAL STATICS 



their solutions in sodium chloride by dilution and the passage of 

 CO2. It is stated by Osborne, however, that the separation which 

 is secured in this manner is rarely so complete as that which is 

 accomplished by dialysis (22). The plant globulins are, accord- 

 ing to Osborne, very readily "denatured" by strong acids, even 

 when diluted. 



For the preparation of some of the seed-proteins it is sufficient 

 to extract the crushed seeds with hot sodium chloride solution; 

 on cooling, the protein crystallizes out spontaneously (6) (19) 

 (29). 



Osborne inclines to the view that the majority of the vegetable 

 globulins, instead of being predominantly acid substances, as they 

 are generally believed to be, are, in reality, predominantly basic. 

 This question will be commented upon in a later chapter (Chap. V). 



9. The Alcohol Soluble Vegetable Proteins (Gliadin, Zein, 

 etc.). — The following method of preparing gliadin, based upon 

 that employed by Osborne and Harris (24), has been communi- 

 cated to me by Dr. J. E. Greaves: 



Gluten is prepared by kneading dough, made from wheat flour, 

 in a stream of cold water until all of the starch has been washed 

 out; it is then partially dried and a moisture determination is 

 made. The moist gluten thus obtained is finely chopped and 

 mixed with twenty times its weight of alcohol of such a strength 

 that with the water in the gluten it forms an alcoholic solution 

 containing 70 per cent of alcohol by volume. The mixture of gluten 

 and 70 per cent alcohol is then allowed to stand, with frequent 

 shaking, for 48 hours. After allowing the mixture to stand for 

 10 hours the supernatant alcoholic solution of gliadin is syphoned 

 off and filtered through very finely shredded and well-washed and 

 dried asbestos until a perfectly clear filtrate is obtained. The fil- 

 trate is then evaporated, under a pressure of about ^ atmosphere 

 until frothing prevents further concentration. It is then cooled and 

 very slowly poured, with constant stirring, into about one hundred 

 times its volume of ice-cold distilled water, containing 10 grams 

 of sodium chloride per litre. The gummy mass, which usually 

 collects on the stirring-rod, is dissolved by the addition of the 

 least possible amount of absolute alcohol, and this solution is 

 evaporated, under reduced pressure, to a thick syrup; the sjo-up 

 is then cooled and poured, in a very fine stream, with constant 

 stirring, into hot absolute alcohol. The precipitate is dissolved 



