60 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



sulphate adhering to it. If we subject the solution to dialysis, 

 part of the globulin 1 separates. This is washed with water. 



Suspended in water it dissolves on the addition of a trace 

 of caustic soda solution and separates again when the solu- 

 tion is exactly neutralized with dilute hydrochloric acid. 

 If the quantity of caustic soda used to dissolve the globulin 

 was too great, then the globulin is not reprecipitated on neu- 

 tralization, as it is kept in solution by the sodium chloride 

 formed. 



III. Reactions Common to Serum Albumin and 

 Serum Globulin. 



For all these reactions use blood-serum which has been 

 diluted with four times its volume of water (20 cc. of blood- 

 serum diluted to 100 cc. 2 ). 



1. A small portion of the solution when heated to boiling 

 changes but little; it becomes somewhat opaque and white 

 by reflected light, but remains transparent by transmitted 

 light. Coagulation does not take place until the fluid is neu- 

 tralized by cautiously adding dilute acetic acid; a slight 

 excess of acetic acid redissolves the precipitate. The solu- 

 tion becomes quite clear on warming. On the addition of a 

 few drops of concentrated salt solution a flocculent precipi- 

 tate of albumin is formed. 



2. To a little of the solution in a test-tube add about one- 

 half the volume of a concentrated solution of salt and divide 

 into two approximately equal parts. One-half is heated 

 to boiling: coagulation takes place. To the other half add 

 acetic acid to distinctly acid reaction : it becomes cloudy even 



1 The quantity of the insoluble globulin which separates is always very 

 small; according to recent investigations (Freund, Marcus: Zeitschr. f. 

 physiol. Chem. 28, 559), this is due to the fact that globulin is for the 

 most part soluble in water. 



2 Correspondingly diluted pathological transudates (ascitic or dropsi- 

 cal fluids) may also be used. 



