A DAIRY LABORATORY GUIDE 37 



EXPLANATION. BOARD OF HEALTH 

 LACTOMETER 



The Board of Health lactometer (commonly called 

 B. of H. lactometer) is an instrument giving ar- 

 bitrary readings and it must be changed to equiv- 

 alent Quevenne readings in order to obtain the 

 specific gravity. It is of the same general shape 

 as the Quevenne, except that the thermometer 

 scale is usually on the opposite side of the stem 

 from the lactometer scale. The instrument is 

 graduated from o to 120, and one degree Board of 

 Health equals .29 of one degree Quevenne. In 

 order, therefore, to change from Board of 

 Health to Quevenne, the Board of Health 

 reading is multiplied by .29. Vice versa to 

 change from Quevenne to Board of Health reading, 

 the Quevenne reading is divided by .29. Like the 

 Quevenne, the Board of Health lactometer is gradu- 

 ated to be read at a temperature of 60° F., and if 

 the temperature is above or below the standard, 

 the correction factor is .3 of one lactometer degree 

 for every degree that the sample is above or below 

 the standard. The following example will illustrate 

 how correction is made: B. of H. reading 110.5 at 

 65° F., what would be the reading at 60° F. ? The 

 sample must be cooled down 5 degrees ; therefore, 

 we would add 1.5 (SX-S) to the reading (110.5), 

 making a corrected reading of 112.0. One of the 

 chief advantages of the B. of H. lactometer is that 

 a small adulteration of the milk will make a notice- 

 able change in the lactometer reading. This is be- 

 cause the instrument has so large a scale. Also, 

 when milk is watered, the number of lactometer 

 degrees recorded below 100 indicates roughly the 

 per cent of adulteration. 



