176 CHEMISTRY FOR AGRICULTURAL STUDENTS 



Fats and Soaps. 



47. What is meant by a '*fat" ? Name the three principal fats, give their 



composition, and mention some of their sources. What are the 

 general properties of fat ? 



48. What is the relation between the molecular weights of the fats and 



their physical properties, including the melting points and specific 

 gravities ? Do the boiling points and solubility of the free acids also 

 vary with the molecular weights ? 



49. What is meant by "saponification"? Show by an equation how 



stearin is saponified by caustic soda. Describe a method for the 

 preparation of soap, and state how the free fatty acid may be pre- 

 pared from it. 



50. Give two methods for the preparation of glycerine from fat. 



51. State the difference between hard and soft soaps, and explain the use 



of soap for washing purposes. 



52. To what is the curd produced by soap in hard water due ? By means 



of equations express the formation of these curds both with the con- 

 stituents which render water temporarily, and also those which 

 render it permanently, hard. 



53. Describe how the temporary and permanent hardness of water can be 



determined. 



54. What is the composition of butter, and how does it differ from all 



other kinds of animal fat ? By what two methods may the purity 



of butter be ascertained ? 

 *55. Accurately determine the melting point of the fat. 

 *56. From the pure Castile soap prepare a specimen of the fatty acid of 



which it is a glyceride. 

 *57. Determine the approximate temporary and permanent hardness of the 



tap water. 

 *58. Is the substance butter or oleo-margarine ? 



Ammonia Derivatives: Alkaloids and Amides. 



59. What is meant by a "substituted ammonia," and in what respects 



will such a compound resemble ammonia ? Give examples. 



60. Give examples of the alkaloids found in plants. How may the alkaloid 



quinine be prepared from its sulphate ? Illustrate the reactions by 

 equations. 



61. Name some amides, and state how the amides differ in their com- 



position from amines. 



62. Mow may urea in the form of nitrate be obtained from urine ? When 



