REVIEW OF THE LITERATURE. 9 



2 to 3 per cent of the gluten was obtained, which corresponds to 0.25 to 0.35 

 per cent of the flour. The actual quantity he considered to be much more, 

 and that in different varieties of wheat the proportion of gluten-fibrin varied 

 greatly. 



Ritthaiisen described gluten-fibrin as insoluble in water, but by boiling 

 with water it was decomposed and rendered insoluble in alcohol. In 

 alcohol of 30 to 70 per cent it dissolved readily when heated, and sepa- 

 rated again on cooling, more completely from the more dilute alcohol. 

 From dilute solutions on concentration and from concentrated solutions on 

 cooling the gluten-fibrin separated on the surface of the liquid as a thick, 

 soft skin, which was renewed as often as it was removed, which property 

 Ritthausen considered distinguished it from mucedin and plant-gelatin. In 

 cold alcohol of 80 to 90 per cent the gluten-fibrin was soluble to a consider- 

 able degree. Dilute acids and alkalis dissolved this protein freely, yielding 

 solutions from which it was precipitated on neutralizing to a slight acid 

 reaction. 



The composition of gluten-fibrin is shown in the table on page 8. 



Plant-gelatin or gliadin formed the fraction of the alcohol-soluble protein 

 that dissolved freely in alcohol of 60 to 70 per cent. The solubility of this 

 protein decreased rapidly when the proportion of alcohol to water fell below 

 or above this strength. It was very slightly soluble in cold water, more 

 so in hot water. By boiling with water it was gradually rendered insol- 

 uble in alcohol. Extremely dilute acids and alkalis dissolved plant-gelatin 

 readily. 



The amount of plant-gelatin which different wheats contain was not deter- 

 mined, owing to the impossibility of separating it from the other proteins. 

 The composition of this protein is shown in the preceding table. 



Mucedin formed the fraction of the alcohol- soluble proteins which was 

 soluble in the most dilute alcohol. Except for its greater solubility in water 

 and in very dilute alcohol, mucedin does not appear to differ greatly in its 

 properties from plant-gelatin. Its composition is given in the table on 

 page 8. 



Mucedin yielded 25 per cent of glutaminic acid when boiled with sul- 

 phuric acid, but other decomposition products were not determined. Only 

 a very small quantity of mucedin was obtained in a pure state, and no 

 estimate of its total amount was made. The relative proportion, however, 

 Ritthausen considered to vary greatly in different sorts of wheat. 



Albumin was obtained by heating the acidified wash- waters of the gluten. 

 This, however, he considered as possibly derived from the soluble part of 

 the gluten-proteins. The composition of this albumin is given in the table 

 on page 8. 



