TESTING 339 



the space between the walls. Lard or tallow serves best 

 for use in this space; a readily inflammable oil should 

 not be employed. The thermometer may be permanently 

 held in place by passing it snugly through a hole bored 

 in a cork, the cork being then fitted into the hole through 

 the flange. A flat metal cover is placed on the cup 

 when making a test. This cover has a hole through 

 the center just large enough to permit the neck of the 

 drying flask to extend up through it. The cover assists 

 in keeping the body of the flask at a constant temperature 

 by preventing the entrance of cold air currents. The 

 thermometer should -register changes in temperature 

 between zero and 200 C. The alcohol lamp should yield 

 a flame about \ inch in diameter and f inch high. The 

 tripod should be about 6 inches high and of proper diam- 

 eter at the top to support the oil bath. 



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 2J 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 diam- 

 eter, with perpendicular walls, and its length should give 

 the flask a total height of 4f 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 



