CH. II.] PROTEOSES AND PEPTONES. 55 



52. Add a little tannic acid : a white precipitate is formed. 



53. Add a little Esbach's or Briicke's solution : a yellow or 

 white precipitate is formed. 



54. Add a little lead acetate solution : a white precipitate is 

 formed. 



55. To 10 cc. of the 5 per cent, solution in a small beaker 

 add 10 cc. of a saturated solution of ammonium sulphate. A 

 white precipitate of the primary albumoses is formed. Stir the 

 mixture vigorously for a short time with a glass rod that has one 

 end covered with a small piece of rubber tubing : allow to stand for 

 a few minutes. The precipitate will usually gather together and 

 can be almost completely collected as a gummy mass on the end of 

 the rod. Transfer it to about 5 cc. of hot water. The precipitate 

 dissolves. Cool the solution and divide it into three portions. 



(a) Add a drop of strong acetic acid and two drops of potassium 



ferrocyanide. A white precipitate is formed, which dis- 

 appears on heating and reappears on cooling. 



(b) To another portion add a few drops of strong nitric acid. 



A white precipitate is formed, which disappears on 

 ' heating and reappears on cooling. 



(c) To the third portion add a drop of copper sulphate solution. 



A white precipitate is formed. 



56. The fluid from which the main mass of primary albumoses 

 has been removed is filtered and treated in a beaker with a single 

 drop of sulphuric acid, and then with ammonium sulphate that has 

 been finely powdered in a mortar. The mixture is stirred vigorously 

 till the fluid is saturated with the salt. A flocculent precipitate of 

 the secondary albumoses (deutero-albumoses) is formed. Collect 

 this ori the rod as before, dissolve in a little water, divide the solution 

 into three parts, and repeat the three tests already performed with 

 the primary albumoses. A precipitate is not formed by any of the 

 reagents. 



57. The fluid from which the secondary albumoses have been 

 removed contains peptone. Filter it, and treat a portion of the 



