166 THE URINE. 



When hippuric acid is heated with mineral acids or alka- 

 lies it decomposes again into glycocoll and benzoic acid. 



359. PREPARATION OF HIPPURIC ACID. Take inter- 

 nally 2 grammes of pure sodium benzoate and collect the 

 urine for the next twenty-four hours. Make it strongly 

 alkaline with milk of lime. Warm, filter, and evaporate 

 the filtrate to a syrup on the water-bath. After it has 

 cooled acidify strongly with concentrated hydrochloric acid. 

 Stir and filter, washing with a little very cold water. Dis- 

 solve the crystals in the smallest possible amount of boiling 

 water. To destroy the coloring matter pass chlorin gas 

 into the hot solution until it is light yellow. Then cool 

 it, filter, and wash the crystals with a very little cold water. 

 If they are still colored they can be still further purified 

 by dissolving in water and boiling with a little animal 

 charcoal. Filter, and let the acid crystallize from the 

 filtrate. Sketch the crystals and hand in sketches. 



360. Heat a few of the dry crystals in a glass tube. 

 They melt and turn red, then give, at first, a hay-like odor, 

 afterward the odor of bitter almonds, from the hydrocyanic 

 acid formed. On the cooler part of the tube is a sublimate 

 of benzoic acid. 



361. On a few crystals in a test-tube pour about a 

 cubic centimeter of concentrated nitric acid, and bring to 

 a boil. Evaporate to dryness in a porcelain dish on a 

 water-bath. The residue, when heated in a dry glass tube, 

 gives the odor of bitter almonds. This test can be used to 

 detect small quantities of hippuric acid. 



362. SEPARATION OF GLYCOCOLL, FROM HIPPURIC ACID. 

 Boil in a flask 1 part of the acid for ten to twelve hours with 4 

 parts of dilute sulphuric acid. Use an inverted condenser to pre- 

 vent evaporation. Let the liquid cool and filter out the benzoic 

 acid. Concentrate the nitrate and mix it in a separatory funnel 



