144 MILK. 



The method of obtaining the milk-sugar has been 

 given. (Experiment 34.) 



323. Test the reaction of fresh milk to red and blue 

 litmus-paper. 



324. Determine the specific gravity with an accurate 

 urinometer. 



325. Eemove the fat from milk by a centrifuge, or 

 after standing, and determine the specific gravity again. 



326. Try the same test after adding from 10 to 25 

 per cent, of water to the milk. 



327. In a weighed porcelain or platinum crucible evaporate 

 10 cubic centimeters of milk to dryness on a water-bath and weigh 

 quickly to find the amount of the total solid matter. The drying 

 will take place much more rapidly if a weighed quantity (about 20 

 grammes) of dried sand is added, but the residue cannot be used 

 for the next experiment. 



328. Heat the dried substance in the crucible, at first gently, 

 then until no black remains. The residue is the mineral matter, 

 or ash. There should not be over 1 per cent, of the weight of the 

 milk. 



329. Compare the action of rennin upon cows' and 

 human milk. Try the rennin in cows' milk to which 50 

 per cent, of water and a few drops of ammonium oxalate 

 have been added to remove the calcium salts. 



330. To separate the nitrogenous constituents of 

 milk first precipitate the casein by saturating the milk 

 (skimmed milk can be used) with sodium chlorid. Filter 

 and to filtrate add powdered magnesium sulphate as long as 

 it dissolves, stirring meanwhile. This precipitate is para- 

 globulin, the same compound that is found in the blood. 

 Filter and apply the globulin tests (Experiments 98 to 

 101). Acidify the filtrate with a few drops of dilute acetic 

 acid and boil. The albumin of milk lactalbumin is co- 



