104 Testing Milk and Its Products. 



perature may be read without taking the lactometer out 

 of the milk; this will give more correct results, will 

 facilitate the reading and save time. 



114. N. Y. Board of Health lactometer. In the East, and 

 among city milk inspectors generally, the so-called New York 

 Board of Health lactometer is often used. This does not give 

 the specific gravity of the milk directly, as is the case with the 

 Quevenne lactometer; but the scale is divided into 120 equal 

 parts, known as Board of Health degrees, the mark 100 being 

 placed at the point to which the lactometer sinks when lowered 

 into milk of a specific gravity of 1.029 (at 60 F.) ; this is con- 

 sidered the lowest limit for the specific gravity of normal cow's 

 milk. The zero mark on the scale shows the point to which the 

 lactometer will sink in water; the distance between these two 

 marks is divided into 100 equal parts, and the scale is contin- 

 ued below the 100 mark to 120. As 100 on the Board of Health 

 lactometer corresponds to 29 on the Quevenne lactometer, the 

 zero mark showing in either case a specific gravity of 1, the 

 degrees on the former lactometer may easily be changed into 

 Quevenne lactometer degrees by multiplying by .29. To fur- 

 ther aid in this transposition, Table III is given in the Appen- 

 dix, showing the readings of the two scales between 60 and 

 120 on the Board of Health lactometer. 



115. Reading the lactometer. For determining the 

 specific gravity of milk in factories or private dairies, 

 tin cylinders, l 1 /^ inches in diameter and 10 inches 

 high, with a base about four inches in diameter, are 

 recommended (see fig. 39) ; another form of specific- 

 gravity cylinder, in use in chemical laboratories, is 

 shown in fig. 40. The cylinder is filled with milk of a 

 temperature ranging between 50 and 70 F., to within 

 an inch of the top, and the lactometer is slowly lowered 

 therein until it floats; it is left in the milk for about 

 half a minute before lactometer and thermometer read- 



