THE PROTEIN SUBSTANCES. 91 



Alkali Albuminates. Strong alkali solutions act very ener- 

 getically on white of egg and the reaction is always accom- 

 panied by some decomposition of the latter. There is a loss 

 of nitrogen in the form of ammonia, and of sulphur as hydro- 

 gen sulphide. The reaction with lead solution, production 

 of lead sulphide, disappears after the alkali treatment. The 

 most characteristic product of alkali action on native albumin 

 is a thick jelly-like mass and is known as " Lieberkuehn's jelly." 

 It may be obtained as follows : 



Ex. Add strong sodium hydroxide solution to white of egg, with 

 constant stirring, until a thick jelly is formed. Too much alkali must 

 not be added here, but just enough to make the maximum of jelly. This 

 is next cut into small pieces and washed in distilled water several times 

 until the lumps are white throughout. They are then heated with fresh 

 pure water, but very gently, until they go into solution. This is then 

 filtered and the filtrate precipitated by acetic acid, avoiding any excess. 

 The precipitate is washed with pure water. 



The alkali albuminates are nearly insoluble in water and 

 dilute salt solutions. The treatment in the above experiment 

 yields finally a moderately pure albuminate which may be dis- 

 solved by addition of excess of weak acid or alkali. 



Ex. Use some of the albuminate of the experiment to test other prop- 

 erties. Dissolve a portion in weak hydrochloric or sulphuric acid and 

 observe that the solution does not coagulate on boiling. An acid solution 

 is precipitated by addition of sodium chloride to saturation, and it is also 

 precipitated by adding weak alkali to the point of neutrality. When this 

 neutral point is reached more alkali brings about solution again. 



The formation of Lieberkuehn's jelly illustrates the produc- 

 tion of the alkali albumin at once in the cold. A similar 

 result is obtained by heating some white of egg solution for a 

 time with very weak alkali. A clear solution is finally obtained. 



Ex. Dilute white of egg with water and add a small amount of N/io 

 alkali solution. A few cubic centimeters will suffice. Keep the mixture 

 at a temperature of about 40 to 45 on the water-bath through an hour, 

 and then test some of it by boiling in a test-tube. It should not coagulate. 

 To a portion of the clear solution add a few drops of phenol-phthalein 

 indicator and then run in dilute sulphuric acid to neutralization. A pre- 

 cipitate forms as shown above. 



