io8 



PHYSIOLOGICAL CHEMISTRY 



the protein tests thus far, whereas the globulin to be studied will be 

 prepared from a vegetable source. There being no essential difference 

 between animal and vegetable proteins, the vegetable globulin we shall 

 study may be taken as a true type of all globulins, both animal and 

 vegetable. 



EXPERIMENTS ON GLOBULIN 



Preparation of the Globulin. Extract 20-30 grams (a handful) of crushed 

 hemp seed with a 5 per cent solution of sodium chloride for one-half hour at 

 6oC. Filter while hot through a paper moistened with 5 per cent sodium chloride 

 solution. Place the filtrate in a water-bath at 6oC. and allow both to cool 

 spontaneously and stand for 24 hours hi order that the globulin may crystallize 

 slowly as the temperature of the bath falls. In case the filtrate is cloudy it should 

 be warmed to 6oC. in order to produce a clear solution. The globulin is soluble 



FIG. 37. EDESTIN. 



in hot 5 per cent sodium chloride solution and is thus extracted from the hemp 

 seed, but upon cooling this solution much of the globulin separates hi crystalline 

 form. This particular globulin is called edestin. It crystallizes in several 

 different forms, chiefly octahedra (see Fig. 37, above). (The crystalline form 

 of excelsin, a protein obtained from the Brazil nut, is shown hi Fig. 38, p. 109. 

 This vegetable protein crystallizes hi the form of hexagonal plates.) Filter 

 off the edestin and make the following tests on the crystalline body and on the 

 filtrate which still contains some of the extracted globulin. 



Tests on Crystallized Edestin. Microscopical examination (see Fig. 37). 



(2) Solubility. Try the solubility in the ordinary solvents (see page 22). 

 Keep these solubilities in mind for comparison with those of edestan, to be made 

 later (see page 114). 



(3) Millon's Reaction. 



(4) Coagulation Test. Place a small amount of the globulin hi a test-tube, add 

 a little water and boil. Now add dilute hydrochloric acid and note that the pro- 

 tein no longer dissolves. It has been coagulated. ' 



