246 THE URINE. 



of the vessel. In pure form it crystallizes in fine needles, which 

 are commonly grouped in sheaves and stars. The salt is almost 

 insoluble in alcohol, and nearly so in water, while free mineral 

 acids dissolve it. 



Kreatinin is further precipitated by mercuric nitrate, notably in 

 the presence of sodium carbonate, by silver nitrate, platinum 

 chloride, stannous chloride, mercuric chloride, picric acid, phospho- 

 tungstic acid, etc. With all these substances it forms well-charac- 

 terized crystalline salts. In alkaline solution it reduces cupric 

 hydroxide, and it is for this reason that urines which contain much 

 kreatinin but no sugar give a positive reaction with Fehling's 

 solution. The separation of the cupric oxide, however, only occurs 

 on prolonged boiling. An alkaline solution of bismuth, on the 

 other hand, is not affected. 



Tests. WEYL'S TEST. A few cubic centimeters of urine are 

 treated with a few drops of a freshly prepared, very dilute solution 

 of sodium nitroprusside, and then drop by drop with a solution 

 of sodium hydrate, when in the presence of kreatinin a ruby-red 

 color develops, which is especially pronounced in the lower portion 

 of the tube. After a few minutes the color disappears. If now 

 acetic acid is added in excess and the mixture heated, it assumes a 

 greenish color, then turns blue, and on standing deposits a sediment 

 of Prussian blue. Acetone and diacetic acid give a similar reaction 

 if ammonia is added instead of sodium hydrate ; but with kreatinin 

 no red color is thus obtained. 



JAFFE'S TEST. If a few cubic centimeters of urine are treated 

 with a dilute aqueous solution of picric acid, the corresponding 

 compound of kreatinin is precipitated. On adding a few drops of 

 a dilute solution of sodium hydrate a red color develops, which per- 

 sists for several hours, and is changed to yellow upon the addition 

 of an acid. With glucose a red color also is obtained, but only on 

 heating, while the reaction in the case of kreatinin takes place only 

 at ordinary temperatures. Acetone gives a reddish-orange color. 



Synthesis of Kreatinin. Kreatinin can be formed synthetically 

 from methyl-glycocoll and cyanamide. Kreatin is first produced, 

 and then yields the anhydride, as shown in the equations : 



/NH 



(1) N=C NH 2 -f NH(CH 3 )CH 2 .COOH = NH=C< 



\N(CH,).CH 2 .COOH 

 Cyanamide. Methyl-glycocoll. Kreatin. 



/NH 2 /NH CO 



(2) NH=C< = NH=Or | +H 2 



X N(CH 3 ).CH 2 .COOH X N(CH 3 ).CH 2 



Kreatin. Kreatinin. 



Isolation and Quantitative Estimation. The quantitative estima- 

 tion of kreatinin in the urine is based upon the formation of the 

 chlorozincate, which is almost insoluble in alcohol : 240 c.c. of 

 urine, which should be free from albumin and sugar, are rendered 



