A DAIRY LABORATORY GUIDE 29 



reading, making the corrected or true reading 32.6. 

 In this case the specific gravity would be 1.0326. 



Familiarity with the action of the lactometer may 

 be obtained by working theoretical problems, of 

 which the following is an illustration : If the 

 lactometer reading of a sample of milk is 31.5 at 

 62° F., what would be the reading at 57° F. ? In 

 this case 57° F. becomes our standard, because it is 

 the temperature to which we are going to lower the 

 sample. Since the sample is 5 degrees too warm, 

 •S (-iXS) of a lactometer degree must be added to 

 the lactometer reading, making the true or cor- 

 rected lactometer reading 32. 



When used in connection with theBabcock test the 

 lactometer 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: 



1. ^^j^i^S. N. F. Babcock's formulae. 



2. yf =S. N. F. Troy's formulae. 



3. Ya L+.2f+.i4=S. N. F. Babcock's modi- 



fied formula. 



Generally speaking, the first formula gives the 

 highest results, 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 formulae L stands for the lactometer 

 reading and F for the fat reading. 



In using these formulae, the following precautions 

 must be especially noted : Board of health readings 

 can never be used in these formulae, consequently 

 B. of H. readings must be changed to Q. ; specific 

 gravity readings cannot be used ; the per cent of 

 fat expressed in hundredths cannot be used. 



