26 



It is the solids-not-fat in milk that cause its specifii: gravity to ex- 

 ceed that of w.ater, and consequently its lactometer reading to be greater 

 than that of water. 



A number of different formulas have been prepared for the calcula- 

 tion of milk solids when the lactometer reading and percentage of fat 

 are known. As the percentage of solids-not-fat increases .25 per cent, 

 for each lactometer degree and .2 per cent, for each per cent, of fat, the 

 following formula has been very generally adopted : 



{% -{- .'I fttt. To find the total solids in a sample ot" milk, add % of the 

 lactometer rea ling to 1.2 times the percent of fat.) 



The following rule is sufficiently accurate for practical purposes and 

 has simplicity to recommend it: To determine the per cent. S.N.F., 

 add the correct lactometer reading and per cent, fat together, and divide 

 by 4. ^=% S.N.F. 



Adulterations. 



By the use of the Babcock test in conjunction with the lactometer, we 

 are enabled to determine both the nature and the extent of dii adulteration. 

 The percentage of fat in milk varies and can also be influenced by 

 skimming, therefore the lactometer alone is of little use in determining 

 adulterations. The solids-not-fat are fairly constant and thus afford a 

 means of detecting adulterations. 



Watered Milk. To find the per cent.- of pure milk in a watered sam- 

 ple, multiply the per cent. S.N.F. in it by 100, and divide by the per 

 per cent. S.N.F. in the pure milk. This subtracted from 100 will give 

 the per cent, of extraneous water in the watered sample. To take an 

 example : 



The per cent, of solids-not-fat in a sample of pure milk is 9 ; but 

 after being watered the per cent, of sollds-not-fat in the watered sample 

 is 7.2. Find the per cent, of pure milk in the watered sample. 



Per cent, of pure milk in watered sample '-"^ * = 80 per cent. 



Per cent, of extraneous water - 100-80=20 per cent. 



Note. When a sample of pure milk cannot be obtained, use 8.5 

 in the early part of the season, and 9 in the later part, for the per cent. 

 S.N.F. in pure milk. 



The per cent, of water added to the pure milk may be estimated a*, 

 follows: The per cent. S.N.F. in a pure sample, multiplied by 100, 

 divided by the per cent. S.N.F. in the watered sample, less 100. The 

 above may be worked as follows. 

 ^^^~^"- equals 25 per cent, water added, or 



To 80 lbs. pure milk, 20 lbs. water were added, then to 

 1 lb. pure milk, f^ lb«;. water were added. 



To 100 lbs. " '-'^^J'^" lbs. water were added. 



80 J 



equals 25 lbs. water added to 100 lbs. milk or 25 per cent. 



