658 THE: MOJONNIER TEST 



wide-mouthed bottle, or 'any other receptacle that permits of cover- 

 ing tightly to prevent evaporation. Allow sealed receptacle to stand 

 in warm room or in warm water until the butter is soft enough for 

 thorough stirring, with table knife, spatula or mechanical stirrer. 

 At 75 to 80 F. butter stirs into a waxy mass from which water or 

 casein will not separate. In this form it is put into boat or flask, to 

 be weighed. 



Butter Fat Determination 



(1). Transfer about one gram of butter sample to butter boat, 

 weigh quickly and insert boat into extraction flask. 



(2). Remove extraction flask from holder and add 9 c.c. hot 

 water. Shake vigorously so as to mix butter and water thoroughly. 



(3). Before replacing flask into holder add 1.5 c.c. C. P. am- 

 monia and shake thoroughly until mixture is complete. 



(4). Add 10 c.c. of 95 per cent alcohol. Insert cork. Re- 

 place flask into holder. Shake thoroughly. Use best quality cork. 



(5). Cool flask by running cold water over lower end of ex- 

 traction flask, if flask is very hot. Otherwise cooling is not neces- 

 sary. 



(6). Add 25 c.c. ethyl ether. Insert cork, shake vigorously 

 * until all butter is dissolved out of boat. Then add 25 c.c. petroleum 

 ether and repeat operation. 



(7). Centrifuge flask, turning handle thirty turns after a 

 speed of about 600 R. P. M. has been reached. 



(8). Pour off extractions into proper weighed 3j^-inch alum- 

 inum dishes. Repeat above extraction, adding successively 5 c.c. of 

 95 per cent alcohol, then 25 c.c. of each of the ethers. For extreme 

 accuracy repeat extraction for third time. The second extraction 

 will remove all but .10 to .15 per cent of the fat. For factory con- 

 trol work, therefore, the third extraction is not necessary. 



(9). Evaporate off ether at 135 C. on fat plate and when 

 all ether is off, dry fat in fat oven held at 135 C. for five minutes 

 after the vacuum has reached at least 22 inches. 



(10). Cool, weigh and calculate per cent butter fat by divid- 

 ing net weight of extracted fat by net weight of sample taken, and 

 multiplying quotient by 100. 



