392 THE ADULTERATION OF MILK 



the fat test is lower than normal, the sample has been skimmed ; 

 while if the lactometer reading is low and the fat is low the 

 sample has been watered, and again if the lactometer reading is 

 normal and fat is low, the sample has been both skimmed and 

 watered. Thus : 



Lactometer low 

 Fat low 



watered 



Lactometer high \ skimmpd 

 Fat low) sklmmed 



Lactometer normal j = skimmed ^ ^^ 



The total food solids of milk may also be determined by the 

 use of the lactometer and Babcock test by the application of 

 the formula : Lactometer reading, divided by 4, plus two-tenths 

 of the fat, equals solids-not-fat. This may be expressed thus : 



-r- + 0.2 f. = per cent solids-not-fat 

 and 



— + 1.2 f. = per cent total solids 



Example : If L = 31.9, temperature 56, corrected L = 31.5. 

 Then if the Babcock test for the sample reads 3.8 per cent fat 

 we have: ^ + .2 X 3.-8 = 8.64 per cent solids-not-fat, and 

 8.64 + 3.8 = 12.44 per cent total solids. 



QUESTIONS 



1. What is a lactometer? 



2. What influence on its reading has temperature? Air and preservatives? 



3. What preservative is most desirable when lactometer determinations are 



to be made? When fat only? 



4. How may skimming and watering be detected? 



5. How may the lactometer and fat test be used to determine the food con 



tent of milk? 



