(c) Lact-albumin, the proteid found in milk. 



2. Preparation of Egg- Albumin Solution. Break a small 

 hole in the end of a fresh egg ; carefully pour out the white 

 of the egg into a beaker. Let the yolk remain in the shell 

 and reserve for later use. Add about twenty volumes of dis- 

 tilled water to the beaker containing the egg-white. Stir 

 thoroughly with a glass rod to break up the membranes and 

 thus liberate the albumin. Filter through a piece of muslin. 

 Any opalescence is due to the precipitation of globulins. 

 Egg-white contains about ii%-i2% of egg-albumin, to- 

 gether with small quantities of globulins, grape-sugar, and 

 mineral matter. 



A good solution for laboratory use maj' also be prepared 

 by dissolving i gram of dry albumin in 200 cc. of distilled 

 water. 



3. Heat 5 cc. of the albumin solution in a test-tube to boil- 

 ing. Notice the coagulation. Add a little nitric acid, the 

 coagulum may turn yellow but it does not di.ssolve. 



4. Xanthoproteic reaction. To a little of the albumin so- 

 lution in a test-tube, add some .strong nitric acid; a precipi- 

 tate is formed, white in color, which on being boiled, turns 

 yellow. After cooling, add ammonia ; the yellow color 

 changes to orange. ■ With weak solutions there may be no 

 precipitate at all. If only traces of albumin are present, the 

 yellow color with the nitric acid may fail to appear, but the 

 addition of ammonia gives the final test with, perhaps, a 

 yellow instead of an orange color. 



5. To another portion of the solution add some of Millon's 

 reagent ; a white precipitate is formed, which on boiling, be- 

 comes brick-red in color. 



6. Piowtrowski's reaction. Add excess of strong solution 

 of caustic potash and then a drop or two of very dilute solu- 

 tion of cupric sulphate, when a violet color results. The re- 

 action occurs more quickly if heat is applied, and the. color 

 deepens. (Peptones and albumoses give a pink color when 

 only a trace of copper sulphate is used.) 



