XX.J 



URIC ACID, ETC. 



133 



11. Tests and Reactions of Kreatinin. 



(a.) Jaffa'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 lb evanescent, passing into a straw colour. 



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

 Fehling's solution. 



FlO. 70. — Ereatlnin-zinc-chloride. a. Balls with radiating marks ; 6. Crystallised 

 from water ; e. Rarer forms from an alcoholic 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 H2SO4. 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 ])and disappears 

 {MacMunn). Its spectrum and composition are practically identical 

 with choletelin CigHjgN203, and it is regarded as an iron-free 

 derivative of haemoglobin on the supposition that it is modified 



