The Lactometer and its Application. 97 



gravity of 1.029 (at 60 F. ); this is considered the lowest 

 limit for the specific gravity of normal cows' milk. The 

 zero mark on the scale shows the point to which the lac- 

 tometer will sink in water; the distance between these 

 two marks is divided into 100 equal parts, and the scale 

 is continued 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 lacto- 

 meter degrees by multiplying by .29. To further aid in 

 this transposition, table III is given in the Appendix, 

 showing the readings of the two scales between 60 and 

 120 on the Board of Health lactometer. 



112. Reading the lactometer. For determining the spe- 

 cific gravity of milk in factories or private dairies, tin 

 cylinders, 1^ inches in diameter and 10 inches 

 high, with a base about four inches in diame- 

 ter, are recommended (see Fig. 38); another 

 form of specific gravity cylinders, in use in 

 chemical laboratories, is shown in Fig. 39. 

 The cylinder is filled with milk of a tempera- 

 ture 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 readings are 

 taken, both to allow the escape of air which 

 has been mixed with the milk in pouring it 

 preparatory to the specific gravity determina- 

 tion, and to allow the thermometer to adjust cylinder. 



itself to the temperature of the milk. The lactometer 



7 



