CHEMICAL PHYSIOLOGY. 



CLASSIFICATION AND PROPERTIES OF THE 

 CHIEF PROTEIDS. 



5. I. Native Albumins are soluble in water, and are not 

 precipitated by alkaline carbonates, sodic chloride, or very dilute 

 acids. They are coagulated by heat at 65 to 73 0. When 

 dried at 40 C. they yield a clear yellow, amber-coloured, friable 

 mass " soluble albumin," which is soluble in water. 



(1.) Egg-Albumin. Prepare a solution as directed in Lesson 

 L, 1. In addition, perform the following experiments : 



(a.) Evaporate some of the fluid to dry ness at 40 0. over a 

 water-bath to obtain " soluble albumin." Study its charac- 

 ters, notably its solubility in water. This solution gives all 

 the tests of egg-albumin. It is more convenient to purchase 

 this substance. 



(b.) Precipitate portions of the fluid with strong mineral 

 acids, including sulphuric and hydrochloric acids. 



(c.) Precipitate other portions by each of the following : 

 Mercuric chloride ; basic lead acetate ; tannic acid ; alcohol ; 

 picric acid (see Lesson XVIII.) 



(d.) Take 5 cc. of the fluid ; add twice its volume of (H 

 per cent, sulphuric acid, and then add ether. Shake briskly 

 = coagulation after a time, at the line of junction of the 

 fluids. 



(e.) The solution is not precipitated on saturation with 

 sodic chloride or magnesic sulphate (compare " Globulins "). 



(2.) Serum- Albumin. Dilute blood serum until it has the same 

 specific gravity as the egg-albumin solution. Neutralise the 

 solution with very dilute acid until a faint haziness is obtained. 



Repeat all the tests for egg-albumin, but, in addition, note 

 that the two solutions differ in the following respects : 



