An ordinary flat-bottom glass Erlenmeyer flask, of such a diameter as to fit neatly into the oil-bath cup, may be used to hold the cheese during the drying operation; but a special glass flask serves better. It is made with a flat bottom 2½ inches in diameter, which will fit into the cup of the drying apparatus. The side walls of this flask should be perpendicular for about 1 inch, when they should begin to slope in toward the base of the neck, which should be located about 2 inches above the bottom. The neck of the flask should be 1 inch in diameter, with perpendicular walls, and its length should give the flask a total height of 4¾ inches. When the apparatus (Fig. 73) is put together for the first time, the melted fat or oil may be placed in the outer jacket and the inner cup may then be fitted into position, or the parts may be put together first and the oil then poured into the space between the cup walls through the opening where the thermometer is to be placed. The oil should fill the space to within an inch of the top. The cork through which the thermometer has been passed is then fitted into the opening. The thermometer bulb should be placed in the oil about half an inch above the bottom of the outer jacket. The apparatus is then placed on the tripod over the alcohol lamp. A flame ½ inch in diameter and ¾ inch high will give sufficient heat to hold the bath at the proper temperature. The temperature may be regulated by raising or lowering the lamp or by changing the size of the flame by adjusting the wick. Hundreds of tests may be run without taking the apparatus apart 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. [Illustration: FIG. 73.--Apparatus necessary to test cheese for moisture.] 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.