URINE. 317 



(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 indicates 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 disap- 

 pear. 



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. 



6. 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 ferrocyanide 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 contain- 

 ing 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 collected from rabbits housed in zinc-lined cages possessed a 

 zinc content which was sufficient to yield a ready response to the 

 test. Zinc is the only interfering substance so far reported. 



7. 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 pre- 

 cipitate 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. 



8. 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 pro- 

 duction of a cloudiness or the formation of a precipitate indicates 



1 Tanret's reagent is prepared as follows: Dissolve 1.35 gram 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. 



