LESSON V 



THE PROTEINS (continued) 



1. Action of Acids and Alkalis on Albumin. Take three test-tubes and 

 label them A, B, and C. 



In each place an equal amount of diluted egg-white, similar to that used 

 in the last lesson. 



To A add a few drops of 0'1-per-cent. solution of caustic potash. 



To B add the same amount of 0'1-per-cent. solution of caustic potash. 



To C add a rather large amount of 0'1-per-cent. sulphuric acid. 



Put all three into the warm bath J at about the temperature of the body 

 (36-40 C.) ; 



After five minutes remove test-tube A, and boil. The protein is no 

 longer coagulated by heat, having been converted into alkali- albumin. After 



PIG. 6. Simple warm bath, as described iu footnote. 



cooling, colour with litmus solution and neutralise with 0'1-per-cent. acid. 

 At the neutral point a precipitate is formed which is soluble in excess of 

 either acid or alkali. 



Next remove B. This also now contains alkali- albumin. Add to it a few 

 drops of sodium phosphate, colour with litmus, and neutralise as before. 



1 A convenient form of warm bath suitable for class purposes may be made by 

 placing an ordinary tin pot half full of water over a bent piece of iron which 

 acts as a warm stage as in the figure. The stage is kept warm by a small gas 

 name. Such a warm bath may be placed between every two or three students. 



