MILK AND ITS PRODUCTS 199 



24. Fat in First and Last Milk. Take a sample from a single 

 co^ by milking the first few streams of milk from each teat into a 

 jar or bottle. Take the last strippings from the same cow in the 

 san:e manner, and test both for fat. 



25. Fat in Milk Sold on the Local Market. Students from homes 

 win re milk is purchased should each bring a sample for testing, 

 tak ng special care to get a fair sample in order that injustice may 

 not be done the milk dealer. 



26. Modified Milk. Using one of the samples of milk pre- 

 vio isly tested, modify it by the addition of water and milk sugar 

 to make it suitable for infant feeding. Modify another sample to 

 maize it suitable for a colt. 



27. Milk of Different Animals. Obtain milk from as many 

 different kinds of animals as possible, mare, sheep, etc., and test 

 for fat. 



ESTIMATION OF TOTAL SOLIDS 



28. Total Solids. For this exercise a Quevenne lactometer and a 

 glass cylinder are required. Bring the milk sample to a temperature 

 of exactly 60 F., and place in the cylinder. Place the lactometer in 

 the milk slowly and carefully. When it comes to rest, note the read- 

 ing at the surface of the milk. By placing 1.0 before this reading we 

 have the specific gravity of the milk. For example, if the reading is 

 32, ohe specific gravity of the milk is 1.032, or that of average milk. 

 The solids not fat and the total solids may be estimated from this 

 and the Babcock reading by using Babcock's formula as follows, in 

 which I is the lactometer reading and / the per cent of fat. 



-r + .2 f . = solids not fat. 

 Solids not fat + fat = total solids. 



Now add one-fourth water to the milk, and repeat the test as 

 described. The results will illustrate one method of detecting 

 water in milk. No attempt should be made to use this method for 

 detecting water, except in an experimental way, unless the user is a 

 trained chemist. 



KEEPING QUALITY OF MILK 



29. Effect of Temperature. When practicable the following 

 experiment can be made advantageously. 



Obtain a quantity of fresh milk, preferably not more than 3 hours 

 after milking. Divide into two parts, cool one part to 50 F. at 



