724 PHYSIOLOGICAL CHEMISTRY. 



Proteins in urine. Albumin in urine is always serum-albumin, 

 and is usually associated with serum-globulin. The pathological con- 

 dition is termed albuminuria. While transient albuminuria may 

 follow severe muscular or mental strain, cold baths, etc., and leave 

 no permanent effect, it must always be regarded as a pathological 

 condition. The most common cause of continued albuminuria is or- 

 ganic disease of the kidneys, acute and chronic nephritis, or even 

 chronic passive congestion. It occurs in all severe febrile conditions, 

 in- blood diseases (pernicious anemia, leukemia), after chloroform and 

 ether anaesthesia, and after many poisons (cantharides, phenol, etc.). 

 Albumin is present in all urines containing blood or pus arising from 

 any portion of the urinary tract. 



Tests for albumin. 



1. Heat and acid. Heat to boiling the upper portion of urine in a 

 test-tube. If a cloud appears it is due to albumin or phosphates. 

 The lower cold urine serves as a guide for comparison. If no cloud 

 forms, albumin may or may not be present ; in any case add a few 

 drops of 5 per cent, acetic acid until the reaction is acid boiling 

 again after each drop. A cloud already present, due to phosphates, 

 will disappear; one due to albumin will become more distinct. In 

 case albumin is present, but has not already been coagulated, it will 

 form a cloud on the addition of the acid, showing that there was not 

 sufficient acid present originally, the urine being either neutral or 

 alkaline. The test is made more delicate by the addition of one-eighth 

 of the volume of the urine of saturated salt solution, which should 

 always be done with very dilute urines. It is important to avoid an 

 excess of the acid, as the coagulated albumin may go into solution 

 again. If the test is made with the addition of salt solution, it is 

 extremely delicate and rarely misleading. The acetic acid may be 

 replaced Ijy nitric acid, with which an excess of acid is less to be 

 feared, and fa to y 1 ^ volume of concentrated acid can be added. 

 With nitric acid the urine should not be boiled after the acid has 

 been added. 



2. Nitric acid test. About 20 c.c. of clear urine are placed in a 

 conical test-glass of about 50 c.c. capacity ; from 5 to 10 c.c. of nitric 

 acid are added by means of a pipette in such a manner that the acid 

 flows slowly from the pipette, which is carried to the bottom of the 

 vessel. Operating carefully, two distinct layers of liquid are obtained, 

 and in the presence of albumin a distinct white cloud will appear at 



