218 AGRICULTURAL CHEMISTRY 



gave this reaction ? (3) What does this indicate that clover con- 

 tains? (4) Why was this compound liberated? 



299. Classification of Proteids. For purposes of 

 study, the proteids may be divided into five classes : (i) 

 Albumins, (2) globulins, (3) albuminates (casein), (4) 

 peptones and proteoses, and (5) insoluble proteids. 



There are some proteids that do not belong to any of 

 the above divisions. The albumin, albuminate (casein), 

 and the insoluble proteids are those found most abun- 

 dantly in plant and animal bodies. 



300. Albumins. The albumins are proteids soluble 

 in water and easily coagulated by heat. Bgg albumin, 

 serum albumin and lactalbumin, are examples of animal 

 albumins. Wheat, oats, rye and nearly all vegetables, 

 when extracted with water, yield some albumin which 

 can be coagulated by heat or precipitation with chemicals. 

 In many vegetables, the albumin is lost when the mate- 

 rial is soaked in water for any length of time. Potatoes, 

 for example, lose a large amount of their albumin if 

 soaked in cold water before boiling. 



Experiment 58. Tests for albumin. In each of four separate test- 

 tubes, place a 3 cc. portion of a solution of egg albumin. To No. i 

 add 3 cc. strong alcohol. To No. 2, add 2 cc. HNO 3 and heat ; 

 when cool, add NH 4 OH. To No. 3, apply heat. To No. 4, add a 

 few drops of lead acetate. 



Questions . ( i ) What change occurred when the solution was 

 heated? (2) When alcohol was added? (3) When HNO 3 was 

 used and heat applied ? (4) What did the Pb(C 2 H 3 O 2 ) 2 do? (5) 

 What do these tests show in regard to the properties of albumin. 



Experiment 59. Albumin and allied proteids from oats. Place 

 in a flask 10 grams of ground oats and 50 cc. of water. Cork and 



