CH. XII.] TOTAL NITROGEN. 313 



out. On dissolving this in strong alcohol, the alcoholic solution 

 shows the colour and absorption band of the original mixture. 



387. Bial's orcin test. To 2 - 3 cc. of urine add 4 - 5 cc. of 

 Bial's reagent and heat till boiling commences. A green colour or 

 the formation of a green precipitate indicates pentoses. The 

 solution shows two absorption bands, one in the red between B and 

 C and the other near the D line. 



NOTE. Bial's reagent consists of i to 1-5 gram, orcine, 500 cc. of concen- 

 trated hydrochloric acid, and 30 drops of a i per cent, solution of ferric 

 chloride. 



9. Lactose. 



Lactose is found in the urine of women during pregnancy, 

 during the nursing period, and soon after weaning. The 

 amount in the urine varies, but rarely exceeds i per cent. 

 The excretion usually reaches its maximum 2 to 4 days 

 after parturition. 



The only satisfactory method of demonstrating the 

 presence of lactose in urine is by the author's test. The 

 mucic acid test is inconvenient and not very reliable. 



388. Cole's test for lactose. To i gram, of good charcoal 

 add 25 cc. of the suspected urine, mix by shaking, boil for a few 

 seconds, cool thoroughly, and shake at intervals for 10 minutes. 

 Filter through a small paper or use a filter pump. When the char- 

 coal has completely drained transfer it to a porcelain dish containing 

 10 cc. of water and i cc. of glacial acetic acid. This is best done by 

 opening the paper, holding it by the clean half and moving it about 

 in the liquid. The greater part of the charcoal is thus removed from 

 the paper. Stir the charcoal with a glass rod and transfer the 

 mixture to a boiling tube. Heat to boiling for about 10 seconds and 

 filter the hot solution through a small paper into a test-tube contain- 

 ing as much solid phenyl-hydrazine-hydrochloride as will lie on a 

 shilling, and twice this amount of solid sodium acetate. Mix 

 thoroughly and filter from any insoluble oily residue. Place the 

 tube in a boiling water bath and leave it there for 45 minutes. 

 Remove the tube and allow it to stand at room temperature for at 

 least one hour. It is advisable to allow it to stand longer if possible. 



