PAKT L CHEMICAL PHYSIOLOai. 



LESSON I. 



THE PROTEIDS AND ALBUMENOIDS. 



The White of Egg may be taken as the Type. 



1. Preparation of a Solution. Place the white of an egg in a 

 porcelain capsule (taking care that none of the yolk escapes), 

 and cut it freely many times with scissors to disintegrate the 

 membranes, and thus liberate the albumin. Add twenty volumes 

 of distilled water, and place the mixture in a flask. Shake well 

 until it froths freely. Cork the flask, and invert it, mouth 

 downwards, over a porcelain capsule ; the membranes will rise 

 to the surface, and, after a time, if the cork be gently withdrawn 

 to allow the fluid to escape, a comparatively clear, or slightly 

 opalescent, fluid will be obtained. If the fluid be too opalescent, 

 strain through flannel or several folds of muslin. Such a 

 solution niters slowly, so that it is better to employ several 

 small filters if a clearer solution be required. If the fluid 

 be alkaline, neutralise it. This solution contains about 5 per 

 cent, of albumin, and diffuses slowly through animal membranes. 



(a.) To some of the fluid in a test-tube add strong nitric 

 acid = a precipitate, which on being boiled turns yellow. 

 Allow the liquid to cool, and add strong ammonia = an 

 orange precipitate or colour (Xanthoproteic Reaction). 



(b.) To another portion add Millon's Reagent = a preci- 

 pitate which becomes reddish on boiling. A red colour of 

 the fluid is obtained if only a trace of proteid be present. 



1 



