TESTING BUTTER AND CHEESE FOR FAT 



the test. Control of the stop-cock can be maintained 

 by giving it frequent and slight movements while the 

 water or acid is running through it.) 



(5) Dissolving the curd. Into the beaker pour 9 

 cc. of cold water; then add n cc. of sulphuric acid 

 (sp. gr. 1.82 to 1.83) and mix by gentle shaking. This 

 mixture is added at once, before cooling, to the con- 

 tents of the funnel and then this is given a rotary 

 motion, with the hand grasping the neck, until the curd 

 is completely dissolved. It is then whirled in the cen- 

 trifuge one minute, after which the acid solution is 

 drawn off until the layer of fat is within a quarter of 

 an inch of the stop-cock. The operation of treating 

 with a mixture of acid and water, whirling, etc., is 

 repeated. 



(6) Separation of fat. The fat now appears as a 

 clear, transparent layer, free from curd, and the solu- 

 tion below it is practically colorless. To separate these 

 two, draw off the latter until the fat nearly reaches 

 the stop-cock, and whirl again for one minute. Then 

 draw off the solution again until the fat just reaches 

 the end of the capillary stem, care being taken to 

 keep the working of the stop-cock under complete con- 

 trol. 



(7) Determination of percentage of fat. The out- 

 side of the separatory funnel is completely dried by 

 wiping with a dry cloth and the funnel is then weighed. 

 The weight of the funnel and fat, minus the weight of 

 the empty funnel, gives the weight of fat in the 20- 

 gram sample. This result, multiplied by 5 gives the 

 percentage of fat in the butter tested. 



(8) Cleaning funnels. After completing each test, 



