88 
LABORATORY MANUAL 
EXERCISE NO. 11 
Object: To determine the effect of the richness of the milk on the efficiency 
of separation, on the relative quantity of cream and skimmilk, 
and the test. 
Procedure: Steadiness in running is one of the most important factors in 
efficiency of separation. Not only is there incomplete sepa¬ 
ration when a bowl vibrates, but there is danger in operating 
such a machine, since the bowl is likely to jump out and burst. 
The cause of a vibrating bowl may be a bent spindle, machine 
not level, changing covers of bowl, unbalanced bowl, unclean 
bowl, worn out bearings, dented bowl, machine not fastened 
down properly, excessive speed, bearings too tight, poor oil, 
or gummed bearing. 
A. Obtain 20 pounds of milk testing approximately 3%, and 20 
pounds of milk testing approximately 4 or 5%. Skim each lot 
separately at a temperature of 90° F. with the separator at 
normal speed. Follow instructions given in Exercise 8. 
Note: Students are to be shifted so that each one is in a new 
position. 
Observations: Machine.No.Capacity. 
(1) Weight of milk . 
(2) Test of milk . 
(3) Pounds of fat . 
(4) Pounds of cream . . . 
(5) Test of cream. 
(6) Pounds of fat in cream . 
(7) Pounds of skimmilk . 
(8) Test of skimmilk .,. 
(9) Pounds of fat in skimmilk .. 
(10) Fat unaccounted for . 
(11) Per cent cream is of milk .. 
(12) Length of test in minutes . . . . . 
(13) Capacity . 
(14) Speed of bowl. 
(15) Temperature of milk. 
Conclusions: 
Questions: (1) If we assume a loss of .04% of fat in the skimmilk and 
250 pounds of cream are obtained from 2200 pounds of 3.5% 
milk, what is the test of the cream? 
(2) W hat is the loss in butter fat if the test of 2520 pounds of 
skimmilk is .17%? 
(3) How many pounds of cream are obtained from 2820 pounds of 
milk testing 3.6% fat if 85% of the whole milk is skimmilk 
testing .03 %? What is the test of the cream? 
(4) Assuming that there are no losses in the skimmilk, how many 
pounds of 35% cream can be obtained from 450 pounds of 
3.2% milk? 
References: Jud. pp. 180-192; St. pp. 224-236. 
