QUESTIONS 339 



will give the amoimt of the rich cream required for the mixture. 

 The difference between the amount of cream desired and the 

 amount of rich cream required will indicate the amount of skim 

 milk required to be mixed with the rich cream to produce the 

 desired result. 



Weight of Cream Per Gallon — Since butter fat is only 

 about 8Y per cent as heavy as skim milk and since the lighter 

 substance varies greatly in amount in cream, it must be expected 

 that the Aveight of a given volume of cream will vary with its fat 

 content. When cream is sold by weight, and paid for by the gal- 

 lon, it is quite important to know the number of pounds in a 

 gallon of cream of varying grades. Below are shown the specific 

 gravity and weight per gallon of water, milk and cream of vari- 

 ous fat contents : 



Weight in Iba. 

 Specific Gravity per Gallon 



Water 1.000 8.34 



Skim milk 1.037 8.64 



4% milk 1.032 8.60 



10% milk 1.025 8.54 



15% cream 1.018 8.48 



20% cream 1.013 8.44 



22% cream 1.011 8.42 



24% cream 1.009 8.40 



~ 26% cream 1.008 8.40 



28% cream 1.006 8.38 



30% cream 1.004 8.36 



35% cream 999 8.32 



40% cream 995 8.29 



QUESTIONS 



1. How doe8 a separator separate? 



2. How much fat is lost in skim milk with gravity creaming? With mechan- 



ical creaming? 



3. What is the normal way of changing the fat content of cream? 



4. Explain reasons for fat variation in separator cream? 



5. How must a separator be set if it is to do good work? 



6. Explain on the board how to modify milk or eream to any given fat 



percentage ? 



7. What is the weight of a gallon of water, skim milk, milk, and 35 per 



cent cream? 



