8 



DAIRY ANALYSIS 



to do this, and the reading may be obtained by ob- 

 serving the point on the stem to which the milk 

 reaches, and adding a constant amount for the height 

 of the meniscus, usually \ degree ; thus in the 

 figure the true reading of the 

 lactometer is 32.5, the apparent 

 reading is 32, and with \ degree 

 added on the true reading is 

 obtained. 



Immerse the bulb of a ther- 

 mometer in the milk, and stir the 

 milk till the temperature is con- 

 stant ; correct the reading to 60 

 F. by means of the table given 

 on p. 88 or by the milk scale 

 (p. 40). To use the table, find 

 in the top line column the 

 specific gravity (or the nearest 

 figure to the left), and in the 

 left-hand column the tempera- 

 ture ; where the lines intersect 

 the corrected specific gravity is 

 given (adding on, if the specific 

 gravity found is not an exact 

 degree, the decimals). 



A thermo - lactometer, i.e. a 

 lactometer which contains a 

 thermometer, may be used, and 

 the temperature can then be read 

 off from the upper scale at the 

 same time as the specific gravity 

 (Fig. 6). 



Never take a specific gravity reading without also 

 noting the temperature and correcting to 60 F. 



The lactometer should be checked by the gravi- 

 metric method, to make sure that the scale is 

 correct. 



A lactometer does not give accurate results if a film 

 of milk is allowed to dry on it ; if a sample has been 



]? IG . 5. Lactometer 

 in Milk. 



The jar in the figure 

 has been filled to the 

 brim with milk in 

 order to show clearly 

 the effect of capil- 

 lary attraction ; it is 

 neither necessary nor 

 advisable to do this 

 when testing milk. 



