53^ Bulletin 281. 



rately balanced. The alcohol lamp is then placed under the iron stand 

 and the asbestos sheet placed on the stand. The lamp is lighted and 

 the cup placed on the asbestos sheet. It is well to light the lamp at 

 least two or three minutes before placing the cup on the asbestos in 

 order to heat the asbestos and save time. The heat of the flame may be 

 increased or diminished by raising or lowering the wick. The cup 

 should always be handled with the hot pan lifter, as by so doing it will 

 be kept clean and errors in weight due to dirt on the cup will be 

 avoided. 



While the sample is heating it should be shaken from time to time, 

 as this breaks up the blanket of casein on the surface and hastens the 

 escape of moisture. As soon as the casein has lost its snow-white color 

 the cup should be removed from the flame. When the moisture has 

 all been driven from the sample, a slightly pungent odor may be noticed. 

 This may also be used as a guide to tell when the sample has been heated 

 enough. The foam begins to subside at this point. Often one or 

 two small pieces of casein are slow to give up their moisture. This is 

 indicated by the snow-white color of the pieces. Evaporation can be 

 hastened by shaking the sample with a rotary motion and thoroughly 

 mixing these pieces with the hot liquid. If this is not done, one might 

 have to heat the sample so long that some of the fat, which had 

 already given up its moisture, would volatilize. 



After all the moisture is driven off, the sample is allowed to cool 

 to room temperature. While cooling, the cup should be covered with 

 something (a sheet of paper will do) to prevent the sample taking up 

 moisture from the atmosphere. After cooling, the cup is placed "on the 

 scales. The sample is lighter than before heating, because it has lost 

 its moisture. The bar of the scales will therefore remain down. The 

 weights are then reversed until the scales just balance. 



Each notch that the larger weight is reversed has a value of 1% 

 (reading on the upper scale), and each notch that the smaller weight 

 is reversed has a value of .1%. If, for example, after heating the scales 

 just balance when the larger weight rests on 15 (upper scale) and the 

 smaller weight rests on .2, it would mean that the sample contained 

 15.2% moisture. 



It may be thought by those using the Cornell test for the first time 

 that the use of the asbestos sheet is unnecessary. It is true that any 

 one who is very familiar with moisture work may heat butter in a direct 

 flame and get fairly accurate results. But the heat of a flame is so intense 

 and butter volatilizes so easily that the use of the asbestos sheet is 

 always advisable. 



