TESTING 341 



or changing the oil. The copper drying cup can be made 

 by any tinsmith. The other parts may be ordered 

 through any dairy or chemical supply company. 



In operating the test, the alcohol lamp is first lighted, 

 so that the oil bath may be warming while the test sample 

 is under preparation. A representative sample of the 

 cheese, which may be taken with a cheese-trier and held 

 in a glass-stoppered sample jar, is then cut into particles 

 about the size of kernels of wheat without removing it 

 from the jar. This may be accomplished with an ordinary 

 table knife that has had the end squared and sharpened. 

 The clean dry flask is then accurately balanced on the 

 scales and a 5-gram weight is placed in the opposite scale 

 pan. Particles of cheese from the prepared sample are put 

 into the flask until the scales comes to an exact balance. 

 Great care should be taken to avoid loss of moisture 

 from the cheese in the preparation of the sample. 



With the thermometer in the oil bath registering 

 between 140 and 145 C. (or between 284 and 293 

 F.), the flask is placed in the cup of the oil bath and 

 the flat disk-shaped cover is adjusted over the ap- 

 paratus. The flask should remain in the bath for fifty 

 minutes, the temperature being kept between 140 and 

 145 C. all the time. The flask is then removed, covered 

 and allowed to cool to room temperature in a dry place. 

 It is then weighed, and the quotient obtained by dividing 

 the loss in weight by the original weight, multiplied by 

 100, gives the percentage of water in the cheese. The 

 following shows the method of computation : 



Problem : Five grams of cheese was heated until the 

 water contained in it was evaporated. The remaining 

 substance weighed 3.15 grams. What percentage of 

 water did the cheese contain? 



