URINE 423 



EXPERIMENTS 

 (The urine should be filtered before performing these tests.) 



Nitric Acid Ring Test (Heller.) Place 5 c.c. of concentrated HNO 3 in a test- 

 tube, incline the tube, and by means of a pipette allow the urine to flow slowly 

 down the side. The liquids should stratify with the formation of a white zone 

 of precipitated albumin at the point of juncture. 



If the albumin is present in very small amount the white zone may 

 not form until the tube has been allowed to stand for several minutes. 

 If the urine is quite concentrated a white zone, due to uric acid or urates, 

 will form upon treatment with nitric acid as indicated. This ring may 

 be easily differentiated from the albumin ring by repeating the test 

 after diluting the urine with 3 or 4 volumes of water, whereupon the 

 ring, if due to uric acid or urates, will not appear. It is ordinarily 

 possible to differentiate between the albumin ring and the uric acid ring 

 without diluting the urine, since the ring, when due to uric acid, has 

 ordinarily a less sharply defined upper border, is generally broader than 

 the albumin ring and frequently is situated in the urine above the point 

 of contact with the nitric acid. Concentrated urines also occasionally 

 exhibit the formation, at the point of contact, of a crystalline ring with 

 very sharply defined borders. This is urea nitrate and is easily dis- 

 tinguished from the "fluffy" ring of albumin. If there is any diffi- 

 culty in differentiation a simple dilution of the urine with water, as 

 above described, will remove the difficulty. Various colored zones, due 

 either to the presence of indican, bile pigments, or to the oxidation of 

 other organic urinary constituents, may form in this test under certain 

 conditions. These colored rings should never be confounded with the 

 white ring which alone denotes the presence of albumin. 



After the administration of certain drugs a white precipitate of 

 resin acids may form at the point of contact of the two fluids and may 

 cause the observer to draw wrong conclusions. This ring, if composed 

 of resin acids, will dissolve in alcohol, whereas the albumin ring will not 

 dissolve in this solvent. 



Weinberger has shown that a ring closely resembling the albumin 

 ring is often obtained in urines preserved for a considerable time by 

 thymol when subjected to the nitric acid test. The ring is due to the 

 formation of nitrosothymol and possibly nitrothymol. If the thymol 

 is removed from the urine by extraction with petroleum ether 1 previous 

 to adding nitric acid, the ring does not form. 



An instrument called the albumoscope (horismascope) has been de- 



1 Accomplished readily by gently agitating equal volumes of petroleum ether and the 

 urine under examination for t-wo minutes in a test-tube before applying the test. 



