46 CHEMICAL STATICS 



vitellin is always associated and probably combined with lecithin 

 are attributable to inadequate extraction of the yolks with ether 

 and the consequent incomplete removal of the lecithin. 



It is extremely difficult to prepare homogeneous solutions of 

 ovovitellin. A five per cent solution in alkali (Ai^/10 KOH) is a 

 thick jelly, opalescent owing to the presence of a multitude of 

 air bubbles entangled in it while stirring. In endeavoring to 

 prepare more dilute solutions it is found very difficult to avoid 

 the formation of small lumps of jelly within the solutions, and 

 these are exceedingly difficult to break up, and dissolve with ex- 

 treme slowness. Although vitellin is soluble in dilute solutions 

 of the strong acids, yet when the powder is directly mixed with 

 an acid solution it will not dissolve or does so with extreme 

 slowness; it is soluble in acid solutions only when freshly pre- 

 cipitated and still wet.* 



It is possible to obtain clear, homogeneous 1 per cent solutions 

 of ovovitellin (not more concentrated) by gradually dropping 

 the vitellin from above into the solvent while undergoing violent 

 stirring, and maintaining the stirring for about an hour. 



8. The Vegetable Proteins. — The following methods of 

 preparing the globulin of flax-seed will serve as an illustration of 

 the general nature of the technique which is employed in pre- 

 paring the various vegetable proteins. For further information 

 concerning this subject the reader is referred to the monograph 

 by Osborne (22) in which he summarizes the result of his impor- 

 tant and extensive researches upon the preparation and properties 

 of the vegetable proteins. According to Osborne (20) flax-seed 

 globulin may be extracted from flax-seed meal in either of three 

 ways, namely by extraction with distilled water, or with sodium 

 chloride solution or with dilute KOH. The following are the 

 methods of preparation employed by him. 



(a) Extraction with distilled water. 



The ground flax-seed is freed from oil by extracting with ben- 

 zene and from the greater part of the outer coating of the seed 

 by sifting through a fine sieve. One hundred grams of this 

 meal are extracted for about 24 hours with distilled water at 

 temperatures between 20 and 40° C. The filtered extract has 

 a yellow color, is acid in reaction and very slightly turbid. 



* Exactly the same phenomenon is encountered with casein. Cf. Van 

 Slyke and Van Slyke (46), T. Brailsford Robertson (32). 



