The Lactometer and Its Application. 105 





 ings are taken, both to allow the escape of air which 



has been mixed with the milk in pouring it, prepara- 

 tory to the specific-gravity determination, and to allow 

 the thermometer to adjust itself to the tem- 

 perature of the milk. The lactometer should 

 not be left in the milk more than a minute 

 before reading is taken, as cream will soon 

 begin to rise on the milk, and the reading, 

 if taken later, will be too high, as the bulb 

 of the lactometer will be floating in partially 

 skimmed milk (23). In reading the lacto- 

 meter degree, the mark on the scale plainly 

 visible through the upper portion of the 

 meniscus of the milk should be noted. Ow- 

 ing to surface tension the milk in immediate 

 contact, with the lactometer stem will rise 

 above the level of the surface in the cylinder, c y linder - 

 and this must be taken into consideration in reading 

 the degrees. It is not necessary to read closer than one- 

 half of a lactometer degree in the practical work of a 

 factory or a dairy. 



116. Time of taking lactometer readings. The spe- 

 cific gravity of milk should not be determined until an 

 hour or two after the milk has been drawn from the 

 udder, as too low results are otherwise obtained (Reck- 

 nagel's phenomenon). 1 The cause of this phenomenon 

 is not definitely understood; it may come from the es- 

 cape of gases in the milk, or from changes occurring in 

 the mechanical condition of the nitrogenous compo- 



1 Milchztg. 1883, 419; bull. 43,Ohem. Div., U.S. Dept. of Agriculture, 

 p. 191; Analyst, 1894, p. 76. 



