PANCREATIC DIGESTION. 99 



washed out by the water, leaving the fat neutral.) If the oil is 

 neutral it will form no emulsion with the carbonate. Add now 

 a drop of a fatty acid like oleic acid and shake. A fine emulsion is 

 formed immediately. 



214. If a bottle of rancid oil is at hand, shake it with a weak 

 solution of sodium carbonate, and notice that it contains enough 

 of the fre'e acids to form an emulsion at once. 



The third ferment of the pancreas, amylopsin, con- 

 verts starch into maltose as the ptyalin does, except that 

 its action is more energetic. Thus it acts upon raw starch, 

 which the ptyalin will not do, or at most only slowly. 



215. Treat boiled and unboiled starch with a small 

 amount of the watery solution of the pancreatic ferments 

 made as before. Test for maltose by Trommels or Feh- 

 ling's test. Notice that it is found with the boiled starch 

 in a few seconds; after a longer time with the unboiled. 



216. To prepare leucin and tyrosin in larger quantities, take 

 of white horn-shavings 2 parts and boil for twenty-four hours with 

 13 parts water and 5 parts of concentrated sulphuric acid, adding 

 water as it evaporates. Dilute with water, and while warm neu- 

 tralize with milk of lime. Filter, boil the precipitate several times 

 with water, and filter in order to remove all the leucin and tyrosin. 

 Unite these filtrates, and, after concentrating them by boiling, pre- 

 cipitate the calcium by the addition of oxalic acid without using 

 an excess. Filter, extract the precipitate with boiling water, 

 unite the filtrates, and evaporate until it becomes a thin syrup. 

 The last of the evaporation should be performed on a water-bath, 

 to avoid burning. Allow it to stand and crystallize. Tyrosin at 

 first crystallizes out, mixed with a little leucin. Filter, concen- 

 trate the filtrate, and allow the leucin to crystallize. 



Another better way to separate the mixed substances is to 

 dissolve them in a large quantity of boiling water to which am- 

 monia has been added. To the boiling solution add basic lead 

 acetate solution until the precipitate formed is nearly white. 

 Filter, heat the filtrate to boiling, neutralize with sulphuric acid, 

 and filter while hot. After cooling, the tyrosin crystallizes and 



