EXAMINATION OF NORMAL AND ABNORMAL URINE 473 



Picric acid test for sugar. It has been mentioned above that picric 

 acid serves as an excellent reagent for albumin ; in the presence of 

 alkalies it may also be used to advantage as a reagent for sugar. 

 Urine is mixed with a few drops of a saturated aqueous solution of 

 picric acid, a little caustic potash is added and gently heated; a 

 marked reddish or reddish-brown coloration, due to the formation of 

 picramic acid, H.C 6 H 2 .NH 2 .(NO 2 ) 2 O, indicates sugar. A reddish 

 color which appears without heating the mixture and which disap- 

 pears completely within twenty minutes indicates the presence of 

 kreatinin. A portion of the reddish liquid heated will turn more 

 intensely red if sugar is also present. 



Molisctis test. This is made by adding to urine a few drops of a 

 10 per cent, alcoholic solution of either thymol, menthol, or alpha- 

 naphthol. Into the inclined test-tube about 2 c.c. of concentrated 

 sulphuric acid are then poured so as to form a layer below the urine. 

 At the zone of contact a color is produced which is red with thymol 

 and menthol, violet with greenish borders with alpha-naphthol. 

 Traces of glucose are shown by these tests. 



Phenyt-hydrazine test is made by heating to boiling a mixture of 

 equal volumes of urine and potassium hydroxide solution, to which a 

 few drops of phenyl-hydrazine have been added. In the presence of 

 sugar the mixture assumes an intense yellow or orange color. Upon 

 supersaturating the cooled mixture with acetic acid a precipitate 

 of golden yellow, r needle-shaped crystals of phenyl-dextros-azon is 

 formed. The test has the advantage that glucose is the only sub- 

 stance likely to occur in urine, which forms these crystals. 



Quantitative estimation of sugar. By far the best method is 

 the decomposition of a copper solution of a known strength, and 

 Fehling's solution prepared as stated above, answers this purpose 

 well. 



1000 c.c. of Fehling's solution, containing 34.64 grammes of crys- 

 tallized cupric sulphate, CuSO 4 .5H 2 O, are decomposed by 5 grammes 

 of grape-sugar, or 1 c.c. of solution by 0.005 of grape-sugar. 



To make the quantitative determination, operate as follows : 10 c.c. 

 of Fehling's solution are poured into a porcelain dish of about 200 c.c. 

 capacity, placed over a flame. The copper solution is diluted with 

 about 40 c.c. of water, and heated to boiling ; to the boiling liquid, 

 urine (which has been previously diluted with 9 parts of water) is 

 added from a burette very gradually, until the blue color of the solu- 

 tion has disappeared, and there remains, upon subsidence of the 



