42 CHEMICAL STATICS 



water in 6 successive washings, the precipitate, after each agi- 

 tation with distilled water, being allowed to settle for 24 hours 

 in the presence of toluol, after which the supernatant fluid is 

 drawn off and the globulin suspended in a fresh quantum of dis- 

 tilled water.* The thick suspension of globulin which is thus 

 obtained after the final washing is kept, in the presence of toluol, 

 in a stoppered bottle and used in this form, since globulin, if 

 washed with alcohol and ether and dried, is redissolved only with 

 difficulty. 



The suspension is well shaken before withdrawing a measured 

 sample. The globulin content of the suspension is determined to 

 within ±0.01 gram per 100 cc. by placing 25 cc. samples in small 

 and accurately weighed beakers, evaporating the fluid to dry- 

 ness on a water-bath, and then drying the residue over H2SO4 at 

 70° until its weight becomes constant. 



4. Fibrin. — The following is the method of preparing fibrin 

 which is employed by Bosworth (2). 



Fresh ox-blood is collected in a large bottle and, as soon as 

 possible, transferred to wide-mouthed precipitating jars and 

 allowed to coagulate. The clots are then removed, broken into 

 small pieces, and washed in running water to remove the serum 

 and blood corpuscles. The washed masses of fibrin are passed 

 through a mincing machine, placed in a large (8-litre) bottle, a 

 little toluol added, and the bottle filled with 0.2 per cent sodium 

 hydroxide solution. This solution causes the fibrin to swell and 

 after about 36 hours the whole content of the bottle resembles a 

 thin jelly. This jelly is broken up, one-half transferred to another 

 8-htre bottle, and after the two bottles are filled by the addition 

 of water they are allowed to stand for an additional 36 hours. 

 The jelly is by then almost completely dissolved and the contents 

 of both bottles are filtered, first through cheese-cloth, then linen 

 and finally paper. The clear filtrate is then diluted with an equal 

 volume of water and placed in tall wide-mouthed precipitating 

 jars. Dilute acetic acid (0.3 per cent) is then added cautiously. 

 At a certain point a flocculent precipitate of fibrin appears which 

 quickly settles to the bottom of the jars. 



* This suspension is, of course, equivalent to a prolonged dialysis of the 

 protein, the precipitate acting as a dialy'ser of enormously extended surface, 

 permitting the passage of associated diffusible impurities into the distilled 

 water and retaining the protein. 



