16 



the addition of ammonia g-ives the final test with, perhaps, a 

 yellow instead of an orang-e 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, (also known as the biuret 

 reaction). Add excess of strong solution of caustic potash 

 and then a drop or two of very dilute solution of cupric sul- 

 phate, when a violet color results. The reaction occurs more 

 quickly if heat is applied, and the color deepens. Make a 

 check test by using some water instead of the albumin solu- 

 tion. (Peptones and albumoses give a pink color when only a 

 trace of copper sulphate is used.) 



7. Adamkiewicz's reaction. Dissolve a small quantity of 

 the proteid by boiling with glacial acetic acid, cool and hold 

 the test tube in an inclined position ; allow 2 cc. of concen- 

 trated sulphuric acid to flow down the side : a violet or purple 

 color develops where the liquids meet. 



8. Acidify another portion strongly with acetic acid and 

 add a few drops of potassium ferrocyanide. A white precipi- 

 tate is obtained. Peptones do not give this reaction. (Al- 

 bumin is also precipitated by lead acetate, mercuric chloride ; 

 picric acid; strong acid, e. g., nitric; tannin; and strong 

 alcohol). 



9. Make some of the albumin solution strongly acid with 

 acetic acid, add a few crystals of sodium sulphate and boil. 

 All proteids except peptones are precipitated in this manner. 

 The filtrate, after boiling, can be used for other tests, (pep- 

 tones) as the acid and sulphate do not decompose thfe solution. 



10. Indiffusibility of Albumin. Place some of the solu- 

 tion in a dialyzer. The salts (crystalloids) diffuse readily. 

 At the next exercise test for chlorides by adding a little silver 

 nitrate solution to a portion of the diffusate. Apply to 

 another portion of the diffusate any of the preceding tests for 

 albumin. None will be found. Albumin belongs to the 

 group of colloid bodies. 



,,\ I'l- '' ■ 11. Globulins are proteids insoluble in water, but are 

 soluble in dilute saline solutions. They are coagulated by 

 heat and are precipitated by saturating their solution with 

 magnesium sulphate or sodium chloride, and by the addition 



r 



