12 TEXT-BOOK OF PHYSIOLOGY 



Palmitic acid occurs in the form of white, glistening scales or needles, 

 melting at 62C. 



Oleic acid is a clear, colorless liquid, tasteless and odorless when pure. 

 It crystallizes in white needles at oC. 



If this saponification takes place in the presence of an alkali e.g., 

 potassium hydroxid or sodium hydroxid the acid produced combines 

 at once with the alkali to form a salt known as a soap, while the glycerin 

 remains in solution. The reaction is as follows: 



' 3 KHO + 3C 18 H 34 2 = 3 KC 18 H 33 2 + 3 H 2 O 

 Potassium Hydroxid. Oleic Acid. Potassium Oleate. Water. 



All soaps are, therefore, salts formed by the union of alkalies and fat 

 acids. The sodium soaps are generally hard, while the potassium soaps 

 are soft. Those made with stearin and palmitin are harder than those 

 made with olein. If the soap is composed of lead, zinc, copper, etc., it is 

 insoluble in water. 



Emulsification. When a neutral oil is vigorously shaken with water 

 or other fluid, it is broken up into minute globules that are more or less 

 permanently suspended; the permanency depending on the nature of the 

 liquid. The most permanent emulsions are those made with soap solutions. 

 The process of emulsification and the part played by soap can be readily 

 observed by placing on a few cubic centimeters of a solution of sodium 

 carbonate (0.25 per cent.) a small quantity of a perfectly neutral oil to which 

 has been added 2 or 3 per cent, of a fat acid. The combination of the acid 

 and the alkali at once forms a soap. The energy set free by this combination 

 rapidly divides the oil into extremely minute globules. A spontaneous 

 emulsion is thus formed. 



THE PROTEINS 



The proteins constitute a group of organic bodies which are found in both 

 vegetable and animal tissues. Though present in all animal tissues, they 

 are especially abundant in muscles and bones, where they constitute 20 

 per cent, and 30 per cent, respectively. Though genetically related, and 

 possessing many features in common, the different members of the protein 

 group are distinguished by characteristic physical and chemic properties 

 which serve not only for their identification, but for their classification into 

 more or less well-defined groups. 



Chemic Composition. A chemic analysis of proteins shows that 

 they consist of carbon, hydrogen, oxygen, nitrogen and sulphur, though 

 the percentage of each of these elements varies somewhat in the different 

 proteins. 



A certain number of proteins contain phosphorus while almost all 

 of them contain different inorganic salts in varying amounts. The average 

 percentage composition of several proteins is shown in the following analyses: 



C. H. N. O. S. 



Egg-albumin 5 2 -9 7- 2 I 5 -6 2 3-9 -4 (Wiirtz). 



Serum-albumin 53 .o 6.8 16.0 22.29 1.77 (Hammers ten). 



Casein.. 52.3 7.07 15.91 22.03 0.82 (Chittenden and Painter). 



Myosin . 52.82 7.11 16.77 21.90 i .27 (Chittenden and Cummins). 



