51 



established as the lowest specific gravity of the milk from a 

 healthy and ordinarily well-fed cow. 



The averagfe lactometer reading- of normal milk is 110, 

 and all milk testing- below 106 must be regarded as doubtful. 



Whenever milk shows less than 106, one of two things 

 may be suspected : First, that the milk contains an unusual 

 amount of cream ; Second, that the milk has been watered and 

 perhaps skimmed. 



It must not be assumed that milk of a low specific gravity 

 is impure, for it may be rich in cream ; nor that milk of a high 

 specific gravity is pure, for it may have been skimmed and its 

 density increased by the removal of the fats. Color, taste and 

 odor will indicate to some extent the quality, but, by the use 

 of the creamometer the percentag-e of cream, in a sample of 

 milk can be determined. 



The thermometer is required to determine the temperature 

 of the milk, since the lactometer is correct only when the milk 

 is at 60° Fahrenheit. The following rule for the correction of 

 lactometer readings is sufficiently accurate for ordinary pur- 

 poses : For each 2J^ degrees of temperature above 6o°, add one 

 to the reading of the lactometer ; example : Lactometer 114, 

 thermometer 70°, or 10° above standard ; add 4 to lactometer 

 reading, making it 118. 



For each 2>^ degrees below 6o°, subtract one from the read- 

 ing of the lactometer ; example : Lactometer 114, thermom- 

 eter 55°, or 5° below standard ; subtract 2 from the lactometer 

 reading, making it li2. 



In testing milk, the following directions should be ob- 

 served : Fill the creamometer nearly full with the milk ; insert 

 the lactometer and note carefully the point on the stem to 

 which it sinks ; take the temperature of the milk and correct 

 the reading of the lactometer according to the rule given above. 

 If the corrected lactometer reading is less than 106, or if it is 

 suspected that the milk has been skimmed, fill the creamometer 

 to the point marked and place it in a cool place, where it 

 will not be disturbed for twelve hours ; in the summer it can 

 be kept in the refrigerator. At the end of that time the cream 

 will have risen and the percentage can easily be read from the 

 scale on the jar. The lowest safe proportion of cream is 15%, 

 and a percentage lower than that will surely indicate that the 

 milk was poor originally, or has been partly skimmed. 



