II. DERIVED ALBUMINS OR ALBUMINATES OR META- 



PROTEINS. 



55. Acid albumin. To a iQ c /c> solution of egg-white 

 add an equal volume of 0.2% HC1 and heat in the water-bath to 

 about 40 C. for a few minutes. Acid albumin is formed. Heat 

 part of this solution. Any coagulation ? Color with litmus and 

 add o.2 f /c KOH from a pipette to neutralization. Result? Add 

 more KOH. Result? 



56. Alkali albumin. Add to io f /c egg-white solution an equal 

 volume of 0.2% KOH and warm at 40 as before. Heat a part of 

 solution. Any coagulation? Color with litmus and neutralize 

 carefully with o.2 f / c HC1. Result? Add more HC1. Result? 



57. Add io c /c KOH to undiluted egg-white in a test-tube. 

 Result? "Lieberkiihn's jelly" is formed which is solid alkali albu- 

 men and will dissolve on warming with water at 40 C. Try simi- 

 larly glacial acetic acid. Result? (Acid and alkali albumin are 

 the first products formed in the digestion of protein in the stomach 

 and in the intestine, respectively.) 



III. SIMPLER PROTEINS. ALBUMOSES OR PROTEOSES 



AND PEPTONES. 



Use a solution of U'itte's "peptone", prepared by dissolving the 

 products of a gastric digest (consisting chiefly of albumoses and 

 peptones) in distilled water. Note carefully the character of the 

 reaction in each case for comparison with the reactions of pure 

 peptones, to be prepared by salting out the proteose. Test as 

 follows : 



58. Heat a portion to boiling. Any coagulation? 



59. Acidulate with acetic acid and add a little K 4 Fe(CN) 6 . 

 Result? AVarm. Result? Cool as before. Result? 



60. Try precipitation with 2 c /c tannic acid, 95% alcohol, 

 saturated HgCl, solution, 3^ CuSO 4 , 2 C / C lead acetate, and picric 

 acid. Note in each case the effect of warming and cooling on the 

 precipitate. 



61. Try the Millon reaction and Adamkiewicz reaction on a 

 little dry peptone powder. 



62. Salting out of proteases and peptones. Saturate a portion 

 of the "Witte's Peptone" solution with solid (NH 4 ) 2 SO 4 and filter. 

 True peptones will be separated from proteoses and be found in the 

 filtrate. Use the filtrate for the following tests. 



1 7 



