72 HANDBOOK FOR BIO-CHEMICAL LABORATORY. 



and an equal volume concentrated sulphuric acid. A red 

 coloration is the result. 



EISELT'S Reaction (Melanin in Urine). Urine containing 

 melanin becomes dark-colored with oxidizing reagents, such 

 as concentrated nitric acid, potassium dichromate, and sulphu- 

 ric acid, as well as with free sulphuric acid. 



EHRLICH'S Reaction (BiliruUn). To a solution of biliru- 

 bin in chloroform add an equal volume or twice its volume of 

 a solution of sulpho-diazobenzol (1 grm. sulphanilic acid, 15 

 c.c. of hydrochloric acid, and 0.1 grm. sodium nitrite, diluted 

 to 1 litre with water). Then add as much alcohol as is 

 needed to render the solution clear. The liquid, which is of 

 a yellow color at first, assumes a beautiful red tint. On add- 

 ing HC1, drop by drop, the color changes first to violet and 

 then to an intense blue. On now carefully pouring into the 

 test-tube a solution of potassium or sodium hydrate three 

 zones of color are visible: near the alkaline solution, where 

 the reaction begins, the color is green; at the surface, where 

 the reaction is still acid, the original blue tint persists; 

 whilst intermediate betweent hese two zones is a red, neutral 

 zone. 



EWALD'S Test (Hydrochloric Acid in contents of stomach). 

 Dilute 2 c.c. of a 10$ solution of potassium sulpho-cyanide 

 and 0.5 c.c. of a neutral solution of iron acetate to 10 c.c. 

 with water. Place a few drops of this ruby-red solution in a 

 porcelain dish and allow 1-2 drops of the liquid to be tested 

 to flow gently thereon. In the presence of HC1 a faint violet 

 cloud is observed where the two liquids come in contact with 

 each other. On mixing the color becomes mahogany brown. 

 Peptones or salts do not interfere with this reaction. 



FEELING'S Reagent (Glucose). 1. Dissolve 34.65 grammes 

 pure copper sulphate in 1000 c.c. water. 



