1902-3.] The Chemistry of Wheat Gluten. 509 



nuclein, also prepared, gave distinct reactions for iron, even after stand- 

 ing for several vveeks under dilute hydrochloric acid, a fact unnoticed 

 by Osborne, and showing that part at least of his nuclein had come from 

 the nuclei of the cells. If this nuclein had been derived from the 

 nuclei of the embryo cells, it must have contained iron, since, as above 

 demonstrated, its presence is invariable in the nucleus. Probably his 

 nuclein was derived both from nuclei and ground substance of the cells. 



It may then probably be admitted that the phosphorus and iron in- 

 variably found in gliadin and glutenin, no matter how carefully they 

 have been prepared, are present in the form of nuclein or nucleic acid, 

 which have been derived from the nuclei of the parenchymatous 

 endosperm cells chiefly, and carried with them in the purification pro- 

 cess. Perhaps aleuron and embryo cells imperfectly separated in the 

 milling process contribute part of them. 



III. — Properties of Gliadin. 



Gliadin extracted directly from raw flour b}' dilute alcohol is 

 always contaminated with fat, which gives to its solution a yellow 

 tinge. On diluting this solution with an equal volume of sodium 

 chloride solution, a snow-white precipitate separates, which, if the dilu- 

 tion is sufficient, collects into brownish flocculent masses, and either 

 rises or sinks, according to the strength of the salt solutions. Prepared 

 in this way gliadin is exceedingly viscid, adhering to everything with 

 which it comes in contact. When precipitated by water alone, gliadin 

 will not readily separate. Evaporation of the alcoholic solution and 

 cooling cause a considerable gummy mass of gliadin to separate, while 

 a few drops of sulphuric acid to the supernatant fluid throw down 

 almost all of the gliadin left in solution. 



A solution of gliadin evaporated to dryness forms a glue-like 

 brittle, opalescent, yellow mass ; hydrated gliadin, exhausted with abso- 

 lute alcohol and ether, and dried over sulphuric acid, forms a pure white 

 friable mass. Either variety will almost wholly go into solution on 

 warming in dilute alcohol. Gliadin is slightly soluble in distilled water, 

 and then gives the pink biuret reaction ; it is not entirely insoluble in 

 dilute salt solutions, as stated by Osborne and Voorhees. In dilute 

 alkalis it readily dissolves, and the greater part of that dissolved 

 separates on neutralizing. Its action with hydrochloric acid is peculiar ; 

 it may be extracted directly from flour by dilute acids, filtered per- 

 fectly clear, and yet an additional drop of acid throws down a cloudy 

 precipitate which increases in quantity with further addition of acid, 



