234 Testing Milk and Its Products. 



A few points .need special attention in using this 

 method: First, care must be taken not to heat the 

 beaker too fast so that spattering occurs ; there is not so 

 much danger from this source when an alcohol lamp is 

 used as with a gas burner, which easily raises the tem- 

 perature too high, causing a fine spray of material to 

 be thrown about, and thus giving too high results for 

 water content. Second, it is important to discontinue 

 the heating at the exact point when all the water has 

 been driven oft' and before burning of the non-fatty 

 solids (casein, milk sugar, and organic acids) occurs, 

 as indicated by a slight darkening in color. It is not 

 necessary to cool the beakers in water, but they can be 

 left to cool in the air. The determination of water in 

 butter by this method can be finished in ten minutes 

 or less by an experienced operator. The Irish test is 

 similar to the method described in the preceding, dif- 

 fering from the same mainly in the shape of the alumi- 

 num dishes used. 



276. Dean's method. Three cc. of a melted sample 

 of butter are placed in an ordinary "patty-pan" tin 

 dish (about 2y 2 inches in diameter and y 2 inch deep) 

 and accurately weighed; the dish is then placed in a 

 steam oven provided with a pop safety valve, a steam 

 pressure gauge, and a thermometer. The oven used 

 by Professor Dean, of Guelph (Ont.) Dairy School, the 

 originator of this method, was 6x8 inches. It was made 

 of galvanized iron by a local tin-smith at a cost of 

 about $5.00, exclusive of safety valve and steam gauge, 

 and was made to withstand a pressure of about 10 

 pounds. After five or six hours' drying in the oven, 



