PHYSIOLOGICAL CHEMISTRY. 



the presence of albumin. The resin acids may interfere here as in 

 the ordinary coagulation test (page 316) but they may be easily 

 differentiated from albumin by means of their solubility in alcohol. 



GLOBULIN. 



Serum globulin is not a constituent of normal urine but fre- 

 quently occurs in the urine under pathological conditions and is 

 ordinarily associated with serum albumin. In albuminuria globulin 

 in varying amounts often accompanies the albumin, and the clinical 

 significance of the two is very similar. Under certain conditions 

 globulin may occur in the urine unaccompanied by albumin. 



EXPERIMENTS. 



Globulin will respond to all the tests just outlined under Albumin. 

 If it is desirable to differentiate between albumin and globulin in 

 any urine the following processes may be employed : 



1. Saturation With Magnesium Sulphate. Place 25 c.c. of 

 neutral urine in a small beaker and add pulverized magnesium sul- 

 phate in substance to the point of saturation. If the protein present 

 is globulin it will precipitate at this point. If no precipitate is pro- 

 duced acidify the saturated solution with acetic acid and warm 

 gently. Albumin will be precipitated if present. 



The above procedure may be used to separate globulin and albu- 

 min if present in the same urine. To do this filter off the globulin 

 after it has been precipitated by the magnesium sulphate, then 

 acidify the clear solution and warm gently as directed. Note the 

 formation of the albumin precipitate. 



2. Half-Saturation With Ammonium Sulphate. Place 25 c.c. 

 of neutral urine in a small beaker and add an equal volume of a 

 saturated solution of ammonium sulphate. Globulin, if present, 

 will be precipitated. If no precipitate forms add ammonium sul- 

 phate in substance to the point of saturation. If albumin is present 

 it will be precipitated upon saturation of the solution as just indi- 

 cated. This method may also be used to separate globulin and 

 albumin when they occur in the same urine. 



Frequently in urine which contains a large amount of urates a 

 precipitate of ammonium urate may occur when the ammonium 

 sulphate solution is added to the urine. This urate precipitate 

 should not be confounded with the precipitate due to globulin. 

 The two precipitates may be differentiated by means of the fact that 

 the urate precipitate ordinarily appears only after the lapse of sev- 

 eral minutes whereas the globulin generally precipitates at once. 



