XX.J URIC ACID, ETC. 133 



11. Tests and Reactions of Kreatinin. 



(a.) Jaffe's Test. Examine the deposit of the zinc compound 

 microscopically. It forms round brownish balls, with radiating 

 lines (fig. 70). 



(b.) Weyl's Test. To urine add a very dilute solution of sodium 

 nitro-prusside, and very cautiously caustic soda = a ruby-red colour, 

 which k> evanescent, passing into a straw colour. 



(<:) A solution of kreatinin reduces an alkaline solution of cupric oxide, e.g., 

 Fehling's solution. 



Flo. 70. Kreatinin-zinc-chloride. a. Balls with radiating marks ; 6. Crystallised 

 from water ; c. Rarer forms from an alcoh"lic extract. 



12. Colouring-Matters of the Urine. (1.) Normal Urobilin, 



which is the principal colouring matter in normal urine. Add to 

 urine neutral and basic lead acetate = a precipitate of lead salts, 

 which carry down with them the colouring matter, leaving the 

 solution nearly colourless. Filter. Extract the pigment from the 

 filtrate by alcohol acidulated with H 2 S0 4 . Filter = alcoholic extract 

 of deep yellow colour, which can be extracted by chloroform. On 

 evaporation of the chloroform it is deposited as a yellow-brown 

 mass, which in an acid solution, shows with the spectroscope one 

 absorption band close to and inclosing F at the junction of the 

 blue and green. On adding an alkali the band disappears 

 (MacMunn). Its spectrum and composition are practically identical 

 with choletelin C 16 H lg N 2 3 , and it is regarded as an iron-free 

 derivative of haemoglobin on the supposition that it is modified 



