URINE. 123 



and will appear as a white ring. As the HN0 3 upon standing 

 diffuses upwards into the urine the ring may become broader. 

 This test is delicate enough for ordinary clinical purposes, 

 but will not show the presence of traces. Urines containing 

 an excessive amount of urea may form a crystalline precip- 

 itate in this test, but such a precipitate cannot be confused 

 with albumin. Colored rings may also form, due to the 

 oxidation of the urinary pigments, and a blue coloration is 

 produced by indican. Substances mentioned under the heat 

 test, such as resins, etc., may form a cloud, but simple tests 

 such as those indicated will exclude them. 



(c) Roberts' Modification of Heller's Test This test is 

 performed similarly to the last by the stratification of a few 

 c.c. of the urine upon 5 c.c. of Roberts' reagent. It has 

 some optical advantages and colored rings never appear in its 

 use. 



(d) Acetic Acid and Potassium Ferrocyanide Test. Acidify 

 5 c.c. of urine with two drops of acetic acid and add, drop by 

 drop, a dilute solution of K 4 FeCN 6 . In the presence of 

 albumin a white precipitate occurs which dissolves in a 

 large excess of the reagent. Traces of albumin may be de- 

 tected with this reaction. Should the precipitate dissolve 

 upon heating, proteoses may be suspected. The presence of a 

 considerable amount of mucin or phosphoprotein in the urine 

 may sometimes give rise to a precipitate with acetic acid 

 alone. This must be removed by filtration before the ferro- 

 cyanide test can be completed. 



(e) Trichlor acetic Acid Test. Stratify a few c.c. of a con- 

 centrated aqueous solution of this reagent with 5 c.c. of 

 urine. A white ring sharply defined indicates the presence 

 of albumin. The precipitate may also be proteoses, but in 

 this case the ring dissolves with cautious warming. This test 

 is more delicate than Heller's, and by its use smaller quanti- 



