II 



14- After washing^ it carefully, stir up the yolk that was 

 saved (2). Put 2 or 3 cc. of the stirred yolk in a test-tube 

 and fill it from ^ to ^ full of ether, and shake several 

 times. The ether soon becomes yellow ; transfer it to an 

 evaporating dish. I,et the ether evaporate at the room 

 temperature, which will not take long, and note that a 

 yellow oil remains. Pour a drop or two of the oil in .some 

 water and notice the globules of fat that are formed. To 

 the remainder of the oil add a few drops of nitric acid. 

 The mixture turns bluish green and finally becomes color- 

 less. Add a few drops oi a I'fo solution of potassium 

 sulphocyanide solution. A reddish color indicates the 

 pre.sence of iron. 



15. The fatty portions of the yolk were dissolved in the 

 ether, and impure vitellin remains in the test-tube. Re- 

 move some of this to a watch gla.ss so that the ether may 

 evaporate. When the substance is free from ether remove 

 it to a test-tube, add some distilled water and note that the 

 vitellin does not dissolve, now add a .small pinch of .salt and 

 .shake ; a milky solution of vitellin is formed. Filter and 

 to portions of the filtrate apply the xanthoproteic, Millon's 

 and Piowtrowski's tests. 



III. 



DERIVED ALBUMINS. 



16. Albuminates. — Action of acids and alkalis on albumin. 

 Take three te.st-tubes and label then A, B, C. In each, place 

 an equal amount of diluted egg-white, like that used at the 

 last exercise. To A add a few drops of o.i % solution of 

 caustic potash. To B add the same amount of 0.1% solu- 

 tion of caustic potash. To C add a rather larger amount of 

 0.1% .sulphuric acid, (i part H^SO, to 1000 of water.) 



