96 MANUAL OF GENEKAL AGBICULTUB^. 



wet precipitate to a small dry beaker and add 30 c.c. of 

 alcohol and stir. Filter a second time and squeeze filter 

 paper as dry as possible. Transfer the precipitate to an- 

 other small beaker ai(id add 50 c.c. ether. Heat on a 

 water bath a little warmer than milk warm, ten minutes, 

 stirring constantly. Filter and save both precipitate and 

 nitrate. The precipitate is the casein. Spread open the 

 paper in order for the ether to evaporate and allow it to 

 dry. Place the dried casein in a weighed dish and weigh. 

 The difference in weights equals the weight of casein. 



To get the per cent of casein in the milk, divide the 

 weight of the casein multiplied by 100 by the weight of 

 milk taken in the beginning, thus: 



grams casein 1AA _ . . ... 



- x 100=% casein in milk, 

 grams milk 



The nitrate contains the fat dissolved in ether. Evap- 

 orate the ether by placing the beaker over a heated water 

 bath and the fat will be left. Weigh and the difference 

 between weight of beaker plus fat and weight of beaker, 

 equals the weight of fat. Get per cent of fat in milk 

 by dividing the weight of fat multiplied by 100 by the 

 weight of milk taken in the beginning, thus: 

 grams fat z 100e=% fat 

 grams milk 



The ether dissolved the fat out of the casein. Casein 

 is not soluble in ether. 



Go back to the first filtrate (after you filtered off the 

 acetic acid from the casein.) Throw away half the solu- 

 tion or save for a second trial and evaporate the other 

 half over a flame. This contains the water, milk sugar, 

 lactic acid, and albumen. As you heat the solution, note 

 the coagulation of the albumen. When the albumen has 

 coagulated, filter. Evaporate the filtrate to dryness, but 

 do not burn it. Sugar will be left. Test with Fehling's 

 solution. (See Exercise 37, a.) Does the milk sugar crys- 

 talize readily? 



(b) To find per cent of solids and ash in milk. 

 Weigh 5 c.c. milk in an evaporating dish. Evaporate it 

 over the flame carefully, taking care not to blacken it, as 



