PHYSIOLOGICAL CHEMISTRY. 



of butyric acid from the butyrin. This may be shown qualitatively by 

 means of the reaction with rosolic acid, a slightly alkaline solution with 

 red color changing to yellow on addition of some of the pancreas-fat 

 mixture. It may also be shown by adding a few drops of phenol-phthalein 

 to some of the mixture and then gradually very weak sodium hydroxide 

 until the alkaline reaction is secured. With a standard alkali solution 

 the volume used becomes a measure of the amount of acid set free. 



In this form of the experiment the butter fat is more readily decomposed 

 than are the more solid neutral fats. Indeed the lighter esters are fre- 

 quently used to detect vegetable lipase through the same general reaction. 

 If in the experiment the butter fat used is not neutral to begin with, it is 

 best to add a few drops of rosolic acid and then very weak alkali until 

 the color just changes to red. Lipase is destroyed by heat as are the 

 other enzymes. 



Ex. The emulsifying power of the pancreas may be shown also. Grind 

 some fresh pancreas to a thin paste with a little water. Add several 

 grams of this mixture to some perfectly neutral refined cotton-seed oil, 

 about 10 cc., in a warm mortar and rub thoroughly with a pestle. After 

 a considerable time an emulsion forms which will bear dilution with much 

 water. With common oil containing a little free fatty acid the emulsion 

 forms more rapidly, but in this case the reaction may be largely due to 

 the formation of soap first, from the combination of the fatty acid and 

 alkali of the pancreatic secretion. The experiment would therefore fail 

 to show the presence of an enzyme as fat splitter. For success here a 

 fresh pancreas is necessary. 



A pure neutral fat suitable for such experiments may be obtained by 

 adding a little caustic soda solution to some refined cotton-seed oil and 

 then ether. On shaking thoroughly the neutral fat dissolves in the ether, 

 leaving the soap formed and excess of alkali undissolved, practically. The 

 fat-ether layer is poured off, shaken several times with water for the 

 removal of traces of soap or alkali, and then slowly evaporated. Neutral 

 fat is left after the volatilization of the ether. 



In these emulsification reactions the pancreatic secretion is 

 assisted by the alkaline bile. According to the theory of the 

 formation of soaps, as a preliminary to absorption from the in- 

 testines, the bile must act as a very important factor, as its 

 alkali would be needed for the purpose. In addition the bile 

 has a distinct solvent action on fatty acids which may be of 

 help in the ultimate passage of the fat products from the 

 intestine. The general nature of the bile products will be 

 discussed later. 



