148 PROTEINS AND AMINO- ACIDS [ch. 



saturate the filtrate with solid ammonium sulphate. The globulins, legumin and 

 vicilin, are precipitated out. Filter off" the precipitate, and then take up in dilute 

 ammonium sulphate (y^Q saturated) and add saturated ammonium sulphate in the 

 proportion of 150 c.c. to every 100 c.c. of the solution {^jj saturation). The legumin 

 is precipitated and can be filtered off". Saturate the filtrate with ammonium sulphate : 

 the vicilin is precipitated and can be filtered off. Dissolve up a little of each preci- 

 pitate in 10 °/o sodium chloride, and boil. The vicilin is coagulated, but the legumin is 

 not. Then dissolve up the remainder of the precipitates in dilute ammonium sulphate, 

 and test both the solutions for protein by the usual reactions [Expt. 127, {a)-{d)]. 



The albumin, legumelin, which occurs only in small quantities in the seeds, can 

 be obtained by dialyzing a water extract of the ground peas until all the globulin is 

 precipitated. On filtering and heating the filtrate, a coagulum of legumelin is formed. 



Proteins of Fat- containing Seeds. 



Of the seeds which contain fat as a reserve material, those investi- 

 gated have been found, in contrast to the cereals, to contain largely 

 globulin as reserve protein. In many cases these globulins have been 

 obtained in crystalline form after extraction from the plant. 



The Hemp-seed (Cannabis sativa) contains one of the best-known 

 crystalline globulins, namely edestin. Pure neutral edestin is insoluble 

 in water but soluble in salt solutions. In the presence of acid, however^ 

 edestin forms salts which are insoluble in salt solutions. Hence a solution 

 of edestin in sodium chloride is precipitated by even small quantities of 

 acids, and, conversely, a solution of edestin in acid is precipitated by 

 small quantities of salt (Osborne, 10). 



Expt. 139. Extraction and crystallization of edestin from Hemp-seed. Take 50 gms. 

 of hemp*seed and grind in a cofiee-mill. Put the ground seed in a large evaporating 

 dish and add 200 c.c. of 5 ''/o sodium chloride solution. Heat with a small flame and 

 stir constantly. A thermometer should be kept in the dish, and the liquid must not 

 rise above 60° C. Filter oflf, in small quantities at a time, keeping the solution in the 

 dish warm. On cooling, the edestin separates out from the filtrate more or less in 

 crystals. To obtain better crystals, filter off the edestin that has been deposited, and 

 pour the filtrate into a dialyzer; add a little toluol, and suspend the dialyzer in 

 running water. As soon as it is cloudy, examine the dialyzed solution for crystals 

 under the microscope. Add a little 5% sodium chloride solution to the original 

 precipitate of edestin in the filter. Make with the filtrate the following tests: 

 (i) The tests for proteins [Expt. 127, {a)-{d\ except Millon's]. (ii) Boil a little of the 

 solution: it is imperfectly coagulated, (iii) Add a little acid: edestin chloride i& 

 precipitated. 



In the Castor- oil seed {Ricinus communis) there is also present a 

 globulin which can be obtained in a crystalline form by the method of 

 Expt. 139. In addition, there is present an albumin, ricin, which has- 

 peculiar toxic properties (Osborne, 10). 



