570 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



5. PATHOLOGICAL URINES. 



(i) DIABETIC. 



Diabetic urine contains glucose ; /?-hydroxybutyric acid, aceto-acetic acid 

 and acetone are often present in diabetes mellitus. 



Glucose. 



The tests for glucose are given under carbohydrates. 



Nylanders Test. 



This reagent has the advantage over Fehling's by not being reduced by 

 creatinine or uric acid. It is reduced by glycuronic acid, i c.c. reagent is 

 added to 10 c.c. urine; on heating, the solution becomes yellow, brown, dark- 

 brown ; metallic bismuth finally separates out. If the quantity of sugar be 

 small, the urine darkens, and after standing for some time, a black de- 

 posit of metallic bismuth settles out. The test will indicate 0^05 per cent, of 

 glucose. 



The Fermentation Test. 



This succeeds well if the quantity of sugar be large, but if the quantity 

 be small as indicated by Nylander's test it may not succeed. The urine is 

 then allowed to ferment for 24-28 hours and is tested again with Nylander's 

 reagent. If Nylander's test is now negative, glucose was originally present ; 

 if positive, the reduction is probably due to other reducing substances, e.g* 

 glycuronic acid, lactose. 



The Phenylhydrazine Test. 



This test is carried out preferably as follows : to 5 c.c. of urine are added 

 2 c.c. of 50 per cent, acetic acid saturated with sodium acetate and 2 drops 

 of phenylhydrazine. The solution is evaporated down to 3 c.c., cooled 

 rapidly, again warmed and then allowed to cool slowly. Crystals separate 

 out even if there be a very small percentage of glucose (Neumann). 



The Polarisation Test. 



The polarimeter distinguishes between glucose, fructose and conjugated 

 glycuronic acid, which is laevo- rotatory. If the urine be highly coloured, it 

 is first precipitated with lead acetate (10 c.c. of a 25 per cent, solution for 

 every 50 c.c. of urine) and the fiitrate examined. The volumes must be 

 known if the glucose is to be estimated by the polarimeter. 



The estimation of glucose is most usually carried out by Pavy's method 

 or by Benedict's method ; the fermentation method (Lohnstein) is convenient. 



Aceto-Acetic Acid. 



Aceto-acetic acid is tested for as follows : 



(1) To some of the urine is added dilute ferric chloride as long as a 

 precipitate of ferric phosphate continues to form. This is filtered off and to 

 the filtrate a few more drops of ferric chloride are added. If aceto-acetic 

 acid be present, the colour becomes like claret. 



(2) Some urine is acidified with sulphuric acid and shaken up with ether. 

 The ether is poured off into another test tube and shaken with ferric chloride 

 solution. A red colour is produced if aceto-acetic acid be present. 



(3) On heating with dilute alkali or acid, the aceto-acetic acid is decom- 

 posed yielding acetone; this may be detected by its odour, but is more 

 certainly detected by distilling and examining for acetone the first 20 c.c. of 

 the distillate from 250 c.c. urine by the following tests: 



(a) lodoform test : NaOH -f I in KI. The precipitate should be ex- 

 amined with a microscope. 



(b) Alcoholic solution of I + NH 3 . lodoform and a black precipitate of 

 nitrogen iodide, which disappears gradually leaving the iodoform, are formed. 



(c) Legal's test. A few drops of freshly prepared sodium nitro-prusside 

 solution are added and it is rendered alkaline with caustic soda. A deep- 

 red colour is formed. If acidified with acetic acid, the colour becomes 

 reddish-purple. 



The estimation of aceto-acetic acid is given on p. 593. 



