6 CHAPTER XXI. 



SOME POOD SUBSTANCES. 



Milk. Contains water 87, solids 13, consisting of casein 

 (ogen) 3, albumin 0-5, fat 3-6, sugar 5, salts 0'7. S.G. 1028 

 to 1034 which is raised by dilution with water. 



1. Reaction amphoteric. Fresh milk reddens blue litmus and 



turns red litmus blue. Due to acid and alkaline phos- 

 phates. Test with litmus paper. 



2. Boil 25 CC milk in a beaker. It does not coagulate. A 



scum forms upon the surface which returns as often as 

 it is removed. Due chiefly to caseinogen entangled in 

 proteid drying on exposure to the air. 



3. Add a few drops of dilute acetic acid to some milk in a 



tube, a floccular pp of caseinoyen and entangled fat 

 results. 



4. Rennet (Extract of calf's stomach). Add a few drops to 



two-thirds of a tubeful of milk, mix, digest at 40 C. in 

 the water-bath. It will curdle in five minutes. From 

 this clot Whey exudes on standing. 



5. To two-thirds of a tubeful of fresh milk add 3 or 4 drops of 



a saturated solution of ammonium oxalate ; mix ; add 5 

 drops of extract of rennet, digest at 40 C for at least 

 half an hour. There will be no coagulum. Then add a 

 few drops of a 2 1XC - solution of calcium chloride. The 

 milk will rapidly coagulate. 



