106 Testing Milk and Its Products. 



perature may be read without taking the lactometer out 

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

 facilitate the reading. 



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. 



The temperature correction for Board of Health lactometers 

 is as follows: for each degree of temperature above 60° F. .3 is 

 added to the reading, and for each degree below, .3 is subtracted.i 



115. Reading the lactometer. For determining the 

 specific gravity of milk in factories or private dairies, tin 

 or copper cylinders are recommended, II/2 inches in 

 diameter and 10 inches high, with a base about four 

 inches in diameter (see fig. 39) ; another form of speci- 

 fic-gravity cylinders, 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 



'A special form of lactometer tbat will allow of very accurate read- 

 ings has been constructed by Poetschke (see Jr. lud. and Eng. Chem., 

 1911, p. 405). 



