74 HANDBOOK FOR BIO-CHEMICAL LABORATORY. 



drying. This yellow color becomes beautifully red on strongly 

 heating, but disappears on cooling, but reappears on gently 

 heating again. 



GENTELE'S Test (Glucose). If a glucose solution is added 

 to a solution of potassium ferricyanide made alkaline with 

 caustic soda or potash, it is decolorized with the formation of 

 potassium ferrocyanide on gently warming. Uric acid also 

 gives this same reaction even in the cold. 



GERHARDT'S Reaction (Aceto-acetic Acid). Aceto-acetic 

 acid gives a wine-red coloration with a dilute, not too acid, 

 ferric chloride solution. In testing urine treat 1-15 c.c. with 

 ferric chloride as long as it gives a precipitate, filter the pre- 

 cipitate of ferric phosphate, and add some more ferric chloride 

 to the filtrate. In the presence of the acid a claret-red color 

 is produced. The urine may also be acidified with sulphuric 

 acid and shaken with ether (which takes up the acid). Now 

 shake the removed ether with a very dilute watery solution of 

 ferric chloride and the watery layer becomes violet red or 

 claret red. The color disappears on warming. 



GERHARDT/S Test (Uroliliri). Extract the urobilin from the 

 solution by shaking with chloroform. Treat this chloroform 

 extract with iodine solution and then a solution of caustic 

 potash, when a beautiful green fluorescence is the result. 



GERRARD'S Test (Glucose). Add a 5$ solution of potassium 

 cyanide to Fehling's solution until the blue color just begins 

 to disappear. On heating this solution to boiling with a glu- 

 cose solution no precipitation of cuprous oxide is produced, 

 but the solution will be decolorized more or less. 



GLOBULIN. See Hammarsten, Polil. 



GLUCOSE. See Almen, Barfoed, Bdttger, Baumann, Baeyer, 

 Braun, Crismer, Felding, Gentele, Gerrard, Haines, v. 



