138 MANUAL OF MILK PRODUCTS 



the Board of Health lactometer is graduated 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 correc- 

 tion 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 (5 X .3) 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 noticeable change in the 

 lactometer reading. This is because the instrument has so 

 large a scale. Also, when milk is watered, the number of 

 lactometer degrees recorded below 100 indicates roughly the 

 percentage of adulteration. 



When used in connection with the Babcock test, the lactom- 

 eter reading is important in obtaining the total solids and 

 solids not fat of milk. There are several of these formulae in 

 use, and while they do not give quite as accurate results as the 

 chemical method, they give results which are accurate enough 

 for all practical purposes. They are as follows : 



n = ^ N F Babcock > s formul8e . 



3.8 



2. LJ? = s. N. F. Troy's formulae. 



4 



3. J L + .2 f + .14 = S. N. F. Babcock's modified formula. 



Generally speaking, the first formula gives the highest re- 

 sults, the second next highest, and the third the lowest results. 

 One can find the total solids by adding the fat reading to the 

 solids not fat. In these formulse L stands for the lactometer 

 reading and F for the fat reading. 



In using these formulae, the following precautions must be 



