23 



40. What is the eifect of adding alcohol to the gelatin 

 solution ? 



41. Add a little solution of mercuric chloride to the gel- 

 atin solution. Note which tests serve to differentiate gelatin 

 from albumin. 



42. Bone. Organic basis obtained by decalcification. 

 Place a small thin dry bone in dilute hydrochloric acid (1 part 

 of the acid to 8 of water) for a few days. Its mineral matter 

 is dissolved out, and the bone, although retaining its original 

 form, loses its rigidity, and becomes pliable, and so soft as to 

 be capable of being cut with a knife. What remains is the 

 organic matrix of ossein. The experiment in the succeeding 

 paragraph may be carried out in a subsequent exercise after 

 the bone has become thoroughly softened. 



43. Wash the decalcified bone thoroughly with water, in 

 which it is insoluble, place it in a solution of sodium carbonate 

 and wash again. Boil it in water, and from it gelatin will be 

 obtained. Neutralize it with sodium carbonate. The solution 

 gelatinizes. Test the solution for gelatin. (31-39). 



Ill 

 CARBOHYDRATES 



44. The term carbohydrates includes an important group 

 of substances, occurring especially in plants. Starch and 

 sugar make up a large proportion of the parts of plants, while 

 cellulose forms tbe chief material from which many parts of 

 plants are constructed. Carbohydrates also occur to a less 

 extent in animals, where they are represented chiefly by gly- 

 cogen and some forms of sugars. 



In elementary composition they are non-nitrogenous and 

 the majority consist of CH and O with the H and O in the 

 same proportion as in water, that is, 2 atoms of H to 1 atom 

 of O. (This proportion is also obtained in other substances 

 not belonging to the carbohydrate group). 



Carbohydrates are indifferent bodies with a neutral reac- 

 tion and form only loose combinations with other bodies, 

 especially with bases. 



