296 METHODS OF ANALYSIS [Chap. 



51 Melted Fat Test.— Tentative. 



Melt 50-100 grams of butter or renovated butter at 50°C. The curd from butter 

 will settle, leaving a clear supernatant fat; in the case of renovated butter, the 

 supernatant fat remains more or less turbid. 



CHEESE. 



52 SELECTION AND PREPARATION OF THE SAMPLE.— OFFICIAL. 



When the cheese can be cut, take a narrow, wedge-shaped segment reaching 

 from the outer edge to the center of the cheese. Cut this into strips and pass 3 

 times through a sausage machine. When the cheese cannot be cut, take the sample 

 with a cheese trier. If only 1 plug can be obtained, take it perpendicular to the 

 surface of the cheese at a point one third the distance from the edge to the center 

 and extending either entirely or half way through it. When possible, draw 3 plugs, 

 1 from the center, 1 from a point near the outer edge, and 1 from a point half way 

 between the other 2. For inspection purposes reject the rind but for investigations 

 requiring the absolute amount of fat in the cheese include the rind in the sample. 

 Either grind the plugs in a sausage machine or cut them very finely and mix carefully, 

 preferably the former. 



53 MOISTURE.— TENTATIVE. 



Place 2-3 grams of very short fiber asbestos (the long fiber may be made suit- 

 able by rubbing it through a fine sieve) in a flat-bottomed platinum dish, 6-7 cm. 

 in diameter, and press the asbestos down firmly. Place in the dish a glass rod, 

 about 5 mm. in diameter and slightly longer than the diameter of the dish. Ignite, 

 cool and weigh the dish and contents. Then weigh into the dish 4-5 grams of the 

 sample, prepared as directed under 52, and mix the cheese and asbestos intimately 

 with the glass rod until the mass is homogeneous. Leave the mass in as loose a con- 

 dition as possible to facilitate the drying. Dry the mixture in an oven at 100°C. 

 and weigh at 1-1| hour intervals until the weight becomes constant (3 weighings are 

 usually sufficient). 



54 ASH AND SALT.-OFFICLAX. 



The dry residue from the moisture determination may be used for the determi- 

 nation of ash. If the cheese be rich in fat, the asbestos will be saturated with it. 

 Ignite cautiously to avoid spattering and remove the lamp while the fat is burn- 

 ing off. When the flame has died out, complete the burning in a muffle at low red- 

 ness. When desired, the salt may be determined in the ash, as directed in 43. 



55 NITROGEN.— OFFICIAL. 



Determine nitrogen as directed under I, 18, 21 or 23, using about 2 grams of 

 cheese, and multiply the percentage of nitrogen by 6.38 to obtain the per cent 

 of nitrogen compounds. 



55 ACIDITY.— TENTATIVE. 



To 10 grams of finely divided cheese add water at a temperature of 40°C. until 

 the volume equals 105 cc, shake vigorously and filter. Titrate 25 cc. portions of 

 the filtrate, representing 2.5 grams of the sample, with standard sodium hydroxid, 

 preferably N/10, using phenolphthalein as an indicator. Express the result in 

 terms of lactic acid. 



