414 PHYSIOLOGICAL CHEMISTRY 



passages. It is probably slightly soluble in the urine. Some investiga- 

 tors believe that the body forming the nubecula of normal urine is 

 nucleoprotein and not a mucin or mucoid as stated above. A discussion 

 of nucleoprotein and related bodies occurring in the urine under patho- 

 logical conditions will be found on page 444. 



NH CO 



I 

 OXALURIC ACID, CO 



I 



NH 2 COOH. 



Oxaluric acid is not a constant constituent of normal human urine, 

 and when found occurs only in traces as the ammonium salt. Upon 

 boiling oxaluric acid it splits into oxalic acid and urea. 



GLUCOSE 



This sugar occurs in traces in normal urine. 1 It is, however, not 

 present in sufficient concentration to be detected by any of the ordinary 

 tests used in urine analysis. In certain pathological conditions (pp. 

 430 and 539) the sugar in the urine is notably increased. Folin has 

 modified Benedict's sugar test (see Chapter XXIV) so it may be used 

 to demonstrate the sugar content of normal urine. 2 



Since glucose is constantly present in urine Benedict 3 has proposed 

 that the term "glycosuria" be discarded and "glycuresis" be used 

 to indicate the presence of an abnormal amount of sugar in the urine. 

 It is believed that 1.5 gram daily is the maximum normal excretion. 



Folin's Test for Sugar in Normal Urine. To about 10 c.c. of urine in a test- 

 tube or small flask add about 2 grams of picric acid and about 2 grams of good 

 quality bone-black (Kahlbaum's or Merck's blood charcoal), shake for five minutes, 

 and filter.* Add i or 2 c.c. of the creatinine-free filtrate to about 10 c.c. of the 

 freshly mixed sugar reagent 5 in a large test-tube (together with a pebble or two to 



: Lancet, 2, 859, 1913. 

 1 Folin: Jour. Biol. Chem., 22, 327, 1915. 

 3 Benedict, Osterberg and Neuwirth: Jour. Biol. Chem., 34, 217, 1918. 



4 Concentrated urines, which give the most trouble in testing for sugar, contain from 3 

 to 5 mg. creatinine per c.c. By the above procedure the creatinine content is reduced to 

 practically nothing at the most a few hundredths mg. per c.c. being left in the nitrate. 

 Bone-black has very strong adsorbing properties for the picrates of creatinine. By allowing 

 the urine and picric acid to stand for a longer time (half an hour or over night) the addition 

 of bone-black may be omitted if desired. The nitrate in that case will contain about o.i 

 mg. per c.c., a quantity too small to interfere with the test for sugar. 



5 Folin's Sugar Reagent. The reagent is made up in two solutions: 



A. Five grams of crystallized copper sulphate are dissolved in 100 c.c. of hot water and 

 to the cooled solution are added 60-70 c.c. of pure glycerol. 



B. One hundred and twenty-five grams of anhydrous potassium carbonate are dis- 

 solved in -400 c.c. of water. 



One part of the glycerol-copper solution (A) is mixed with two parts of potassium car- 

 bonate solution (B). Only small portions should be mixed at a time as the reagent (after 

 mixing) does not keep but undergoes gradual reduction. 



