NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 217 



permanent yellow color; (2) a solution of mercury and 

 nitric acid, known as Millon's reagent, gives a brick-red 

 color with the acid if heated ; (3) a solution of copper 

 sulfate and potassium hydrate gives a violet- colored solu- 

 tion. The proteids, found in living cells, have different 

 properties from those in dead tissue. Proteids readily 

 undergo oxidation, and are chemically altered in the 

 preparation of many foods. When the protein molecule 

 is acted upon by heat, a large number of products are 

 formed, as fatty acids, amides, aromatic bodies, ammonia, 

 and carbohydrate-like bodies. The most common change 

 which the proteids undergo is the rearrangement of the 

 atoms and radicals in the molecule. The coagulation 

 of albumin by heat is a chemical reaction in which the 

 atoms and radicals in the albumin molecule are sim- 

 ply rearranged structurally. The fact that it is possi- 

 ble for such a large class of compounds as the proteids 

 to be composed of only a few common elements, and 

 for the various members to have different properties, 

 is accounted for by differences instructural composi- 

 tion. 



Experiment 57. Testing for nitrogenous organic compounds. 

 Mix 0.5 gram dry clover with enough soda lime to half fill a test- 

 tube. Connect the test-tube with a delivery tube, one end of 

 which leads into another test-tube containing water. Apply heat 

 for from five to seven minutes. Test the distillate with test paper. 

 (Soda lime has the power to decompose proteid material and 

 liberate the N as NHj. The C and O of the proteid unite and form 

 CO 2 and H 2 O.) 



Questions. ( i ) What reaction was obtained when the distillate 

 was tested with litmus ? (2) What compound was produced which 



