296 DETECTION OF ADULTERANTS AND PRESERVATIVES 



cock test. The samples should have a temperature of 55 to 65 de- 

 grees F. In summer and at any other time when the temperature 

 naturally is much higher or lower, place the sample jars into a tank 

 or tub of water at the desired temperature, from one-half hour to 

 an hour before testing. For directions for the use of the lactom- 

 eter and the Babcock tester, see "Milk," Chapter XXXI, page 262. 

 If the milk contains corrosive sublimate, deduct one-half point from 

 the lactometer reading for each tablet in one pint of sample. 



INTERPRETATION OF RESULTS. The lactometer reading and the 

 per cent fat alone furnish a pretty safe index to the freedom from, 

 or presence of adulteration of the milk. From these two factors 

 other guides, such as the specific gravity, per cent of total solids 

 and per cent of solids not fat of milk, and specific gravity of the 

 milk solids may be calculated. These are of additional assistance to 

 the inspector. All of these factors vary considerably with the indi- 

 viduality, breed, period of lactation and feed of the cows, so that 

 considerable latitude must be allowed in determining whether or not 

 any given sample of milk has been adulterated. These variations 

 are greatest between individual cows and between different breeds, 

 but they also are quite striking in milk of the same cows from day 

 to day and at different stages of the period of lactation. In mixed 

 herd milk, such as the condensery largely receives, the composition 

 is comparatively uniform on consecutive days. Whenever possible, 

 in the case of suspicious milk received at the factory, samples 

 should be secured direct from the stable for comparison. 



The following may be considered reasonable limits of compo- 

 sition beyond which normal milk seldom trespasses, and milk not 

 falling within these limits may be regarded with suspicion. 



