490 APPENDIX 



(a) Fill a test tube one fourth full of the mixture and boil. 

 The albumen coagulates. 



(<) Prepare another tube and add a few drops of nitric acid. 

 The albumen coagulates. Boil. The coagulated mass turns 

 yellow. Cool the tube and add ammonia. The color deepens 

 to orange. 



(V) Prepare another tube and add a few drops of Millon's 

 reagent. The albumen is coagulated, and, on boiling, turns red- 

 dish. If only a little proteid is present no coagulation will occur, 

 but the mixture will redden when boiled. 



(d) Make the contents of another tube strongly acid with 

 acetic acid, then add a few drops of potassium ferrocyanide, 

 and a white precipitate will form. 



(2) Some of the chemical reactions of digested pro teids 

 {peptones} 



Make a peptone solution by dissolving some of Merck's pep- 

 tone in water. Repeat the experiments given for proteids. 

 Results similar to those in (b} and (c) will be obtained, but 

 the peptone does, not coagulate on boiling, nor does it give the 

 white precipitate with acetic acid and potassium ferrocyanide. 



(3) To show that peptones are diffusible through membranes, 

 while proteids are not 



Prepare the two dialyzers as for the experiments with starch 

 and grape sugar. Into the inner jar of one dialyzer put some 

 of the white-of-egg mixture, and into the other some peptone 

 solution. After a few hours test the water in the outer jar of 

 each dialyzer. It will be found that the peptone passes through 

 the membrane, while the proteid does not. 



(4) To show that the gastric juice digests proteids, i.e., 

 changes them to peptones 



Prepare some artificial gastric juice as follows : Make some .2 

 per cent hydrochloric acid by mixing 5.5 cubic centimeters 

 of hydrochloric acid (sp. gr. 1.16) with enough distilled water 



