UROMELANINE. 189 



calcined magnesia till a filtered sample is free from 

 phosphoric acid. Filter the whole, and to the solution 

 add some concentrated sulphuric acid drop by drop, 

 shaking well, until strongly acid. Filter and distil in 

 a retort for six hours, replacing the water as it evapo- 

 rates, and adding more sulphuric acid if necessary. 

 The distillate will contain volatile acids (q. v.) and 

 essential oil (q. v.) 



2. The residue in the retort must be mixed with two 

 volumes of water and allowed to stand. A brown-red 

 resinous precipitate will be formed. Filter. 



3. Evaporate down the nitrate, again precipitate 

 with water and filter, and again concentrate and 

 allow to stand ; crystals of hippuric acid will probably 

 be deposited (q. v.). 



4. The resinous precipitate is well washed with cold, 

 then with boiling, water, and boiled with 90% alcohol. 

 Omicholine, omicholic acid, and uropittine (q. v.) dissolve 

 in the alcohol, while uromelanine remains as an in- 

 soluble black powder. 



5. Wash the uromelanine with boiling alcohol, then 

 with water, dissolve in very weak caustic potash, filter, 

 acidify with dilute sulphuric acid, wash the precipitate 

 with water and hot alcohol, and dry. 



6. Uromelanine is insoluble in water and dilute 

 acids, very slightly soluble with a red colour in alcohol, 

 extremely soluble with a brown-black colour in 

 alkalies. 



7. Dissolve in acetic acid, and add to the solution 

 mercuric nitrate. A red precipitate will appear. 



8. Dissolve in concentrated sulphuric acid, mix the 



