the tube a small piece of moist red litmus paper and a piece of 

 moist lead acetate paper (strip of filter paper soaked in 2 f -/ ( . lead ace- 

 tate and dried). Heat the lower end of the tube, and note the 

 characteristic odor of burned feathers. If ammonia is evolved 

 (showing the presence of X and H ), the litmus paper will turn blue ; 

 if sulphur, the lead acetate will turn black, through formation of lead 

 sulphide. If the albumen chars black, the presence of C may be 

 inferred. State the results of your conclusions as to the presence 

 of C, X, H, and S in proteid. 

 C. TESTS FOR PROTI-: IN. 



43. Xanthoproteic reaction. Dilute some of the \Q f /c egg-white 

 till it is about 2/r , and place in a test-tube. Add a few drops 

 of cone, nitric acid. \Yhat occurs? Boil. \Yhat occurs, as to 

 color and other changes? Cool the solution and add ammonia. 

 Be careful that the contents of the tube do not shoot out. X T ote 

 the color produced (this is the essential feature in xanthoproteic 

 reaction ). Describe and fix in mind this reaction. 



44. Does gelatin give the xanthoproteic reaction ? Try in the 

 same way a weak solution of gelatin. Does fibrin (obtained from 

 the blood ) ? Try this reaction also with a small piece of meat, and 

 a small piece of bone or cartilage. 



45. Millon's reaction. To a little of the dilute solution of albu- 

 min add a few drops of Millon's reagent. ( This has been made as 

 follows: dissolve one part of mercury in an equal weight of [cold] 

 nitric acid. Then add the solution to twice its volume of water, 

 allow to stand some hours, then decant off the liquor from the 

 sediment. ) Note the white precipitate formed when Millon's reagent 

 is added to the albumin. Boil two or three minutes, and observe 

 the result ? 



46. Does gelatin give Millon's reaction? Does meat? First 

 boil a small piece of meat to destroy the red color. Does bone? 



47. The binrct test. To a little of the dilute albumin solution 

 add an equal volume of io c /c potassium hydrate and add one or 

 two drops (or more is necessary) of l /2 c /c copper sulphate. Notice 

 the violet color. Try the biuret reaction with gelatin, caseinogen 

 and peptone solutions. 



48. Adamkiewics's reaction. Place in a dry test-tube ten drops 

 of strong sulphuric acid and 20 drops of glacial acetic acid 

 containing glyoxylic acid. To this mixture add a little dried albumin 

 and warm slightly. Notice the reddish violet color, due to trypto- 

 phane. Try this with some dry gelatin. 



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