BY JAMES M. PETRIE. 813 



have obtained by successive extraction with (1) dilute salt solution, 



(2) 70 % alcohol, (3) 0-2 % alkali, the following :— 



Edestin 0*6 % globulin / sol. in j separated by dialysis. 



Leucosin. ... 0*3 albumin j salt > separated by heat-coagulation. 

 Proteose.... 0'6 ' solutions ) remains in solution. 



Gliadin 4*2 sol. in 70% alcohol I rl , 



Glutelin 4M) sol. in dil. alkali ) umten - 



97 %. Total proteins in wheat flour. 



In a similar manner they have obtained from maize three 

 globulins, two albumins, and the alcohol-soluble protein, zein(37). 

 From the pea (Pisum sativum) three proteins were isolated, (38) 

 viz., two globulins — legumin and vicilin, and tho albumiu 

 legumelin. 



The legumin of peas and beans, and the gluten of wheat were 

 the earliest known of the plant-proteins, having been discovered 

 more than a hundred years ago. They were classed with the 

 " sanguigenous compounds" of the early chemistry. On this 

 heterogeneous group the first light dawned with the classical 

 researches of Ritthausen in 1872. which are summarised in his 

 book " Die Eiweisskorper der Getreidearten." For the extraction 

 of proteins he used dilute acids and alkalies as solvents, but these 

 have since been proved to alter the proteins and are now given up. 



Osborne in obtaining legumin from the garden-pea, first made 

 an extract with 10 % sodium chloride solution, from which the 

 total proteins were precipitated by salting out with ammonium 

 sulphate. The proteins were redissolved and dialysed free from 

 salt, when the globulins were rendered insoluble and the albumins 

 remained in solution. The precipitate of globulins was next 

 dissolved in dilute salt solution and fractionally precipitated by 

 different concentrations of ammonium sulphate. He found that 

 up to six-tenths saturation precipitated legumin, while above this 

 strength up to complete saturation precipitated the vicilin. The 

 legumin thus obtained was purified, and hydrolysed by boiling 

 with acid, the product esterified by Fischer's new method,(39) and 

 the esters separated by fractional distillation; from the various 

 fractions the amino-acids were obtained. A second part was 

 then hydrolysed, and the hexone bases separated by the method 

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