136 MODERN METHODS OF TESTING MILK 



Corrections for temperature. In using the B. of 

 H. lactometer, correction is made for temperatures 

 above or below 60 F. For each degree of tempera- 

 ture of milk above 60 F., add .3 to the lactometer 

 reading, and for each degree below 60 F. subtract .3 

 from the reading. 



PRECAUTIONS IN TESTING SPECIFIC GRAVITY 

 OF MILK 



1. Milk should, for best results, not be examined 

 until i to 2 hours or more after milking, since the 

 specific gravity of milk is lower for a while after be- 

 ing drawn than it is later, due chiefly to the presence 

 of gases. 



2. The sample of milk must be completely mixed. 



3. The lactometer must be kept clean. 



4. In milk which has been preserved by potassium 

 bichromate, the specific gravity is about one degree 

 higher than in the normal milk, in case the usual 

 amount of bichromate has been added. (See p. 30). 



VALUE OF LACTOMETER IN DETECTING ADUL- 

 TERATED MILK 



The value of the lactometer in detecting adulterated, 

 especially watered, milk was formerly overestimated. 

 Taken alone, the results given by the lactometer may 

 be thoroughly unreliable and misleading. It has 

 come to be quite generally recognized that the proper 

 use of the lactometer in milk inspection is largely to 

 indicate whether a sample is suspicious and to furnish 

 a guide as to whether it is necessary to take a sam- 

 ple for further detailed investigation by chemical anal- 



