66 MODERN METHODS OF TESTING MILK 



with the eye. Notice the divisions marking the high- 

 est and lowest limits of the fat-column. The differ- 

 ence between them gives directly the per cent, of fat 

 in the milk tested. The readings can be made accu- 

 rately to one-half of a division, that is, to one-tenth of 

 one per cent. Some test-bottles are provided with a 

 regulator which moves the bottom of the fat-column 

 to a level with the nearest numbered mark. 



In connection with the measuring of the fat-column, 

 the following points deserve attention : ( i ) Using divi- 

 ders to assist in reading, (2) the temperature of the 

 fat-column, (3) the upper and lower limits of the 

 fat-column, (4) the correct appearance of the fat- 

 column, (5) defects in appearance of the fat-column. 



(1) If one uses test-bottles not provided with a reg- 

 ulator for adjusting the level of the fat-column, the 

 reading of the percentage of fat on the scale may be 

 made with less liability of error by measuring the 

 length of the fat-column with a pair of dividers, one 

 point of which is placed at the bottom and the other 

 at the upper limit of the fat-column. The dividers 

 are then removed and one point is placed on the zero 

 mark of the scale on the bottle used, when the other 

 point will be at the exact per cent, of fat in the milk 

 tested. 



(2) The temperature of the fat, when it is read or 

 measured, should be above 120 F. and not above 

 140 R, preferably about 130 F. This will insure 

 sharply defined upper and lower limits of the fat-col- 

 umn. In case the contents of the bottles are below 

 120 F., the bottles should be placed for 15 or 20 min- 

 utes in water that has a temperature of 130 to 140 F., 



