URINE 425 



fluid must be acid to secure the complete precipitation of the albumin by this 

 coagulation process. 



Too much acid should be avoided since it will cause the albumin to 

 go into solution. Certain resin acids may be precipitated by the 

 acid, but the precipitate due to this cause may be easily differentiated 

 from the albumin precipitate by reason of its solubility in alcohol. 



(b) A modification of this test in quite general use is as follows : Fill a test- 

 tube two -thirds full of urine and gently heat the upper half of the fluid to boiling, 

 being careful that this fluid does not mix with the lower half. A turbidity indi- 

 cates albumin or phosphates. Acidify the urine slightly by the addition of 3-5 

 drops of dilute acetic acid, when the turbidity, if due to phosphates, will disappear. 



Nitric acid is often used in place of acetic acid in these tests. In 

 case nitric acid is used ordinarily 1-2 drops is sufficient. 



5. Acetic Acid and Potassium Ferrocyanide Test. To 5 c.c. of urine in a 

 test-tube add 5-10 drops of acetic acid. Mix well and add potassium ferro- 

 cyanide drop by drop, until a precipitate forms. 



This is a very delicate test. Schmiedl claims that a precipitate of 

 Fe(Cn) 6 K 2 Zn or Fe(Cn) 6 Zn 2 is formed when urines containing zinc 

 are subjected to this test and that this precipitate resembles the 

 precipitate secured with protein solutions. In the case of human 

 urine a reaction was obtained when 0.000022 gram of zinc per cubic 

 centimeter was present. Schmiedl further found that the urine col- 

 lected from rabbits housed in zinc-lined cages possessed a zinc content 

 which was sufficient to yield a ready response to the test. 



Proteoses may also be detected by this test. To differentiate 

 albumin from proteose perform the coagulation test (see page 424). 



6. Tanret's Test. To 5 c.c. of urine in a test-tube add Tanret's reagent 1 drop 

 by drop until a turbidity or precipitate forms. This is an exceedingly delicate test. 

 Sometimes the urine is stratified upon the reagent as in Heller's or Roberts' ring 

 test. According to Repiton, urates interfere with the delicacy of this test. Tanret, 

 however, claims that urates do not interfere inasmuch as any precipitate due to 

 urates may be brought into solution by heat, whereas an albumin precipitate under 

 the same conditions will persist. Tanret further states that mucin interferes with 

 the delicacy of the test and that it should therefore be removed from the urine 

 under examination by acidification with acetic acid and filtration before testing for 

 albumin. This test also serves to detect proteoses. 



7. Sodium Chloride and Acetic Acid Test. Mix two volumes of urine and one 

 volume of a saturated solution of sodium chloride in a test-tube, acidify with acetic 

 acid, and heat to boiling. The production of a cloudiness or the formation of a 

 precipitate indicates the presence of albumin. The resin acids may interfere here 



1 Tanret's reagent is prepared as follows: Dissolve 1.35 grams of mercuric chloride in 

 25 c.c. of water, add to this solution 3.32 grams of potassium iodide dissolved in 25 c.c. of 

 water, then make the total solution up to 60 c.c. with water and add 20 c.c. of glacial acetic 

 acid to the mixture. 



