182 BUTTER-MAKING. 
lieve that the last few degrees the milk is being heated are the 
most expensive; but if the steam is properly guarded from 
being condensed, or wasted, it does not cost any more to heat 
the milk the last few degrees than it does to heat the first degrees. 
While the temperature on the milk side is low, much more 
steam is consumed, and it is also used more rapidly. During 
the last heating of the milk or cream less steam is being con- 
densed and the condensing proceeds more slowly. 
When the temperature on the steam side is 220° F. and on 
the milk side is 40° F. during the same time, twice as much 
heat will pass through the heating wall as if the temperature 
of the milk side were 130° F. In the first case the difference 
in temperature on both sides would be: 220—40=180° F. In 
the second instance it would be: 220—130=90°. F. 
(5) Proper Utilization of Steam Turned into the Pasteurizer. 
—The cost of pasteurization will evidently vary under different 
conditions and with different kinds of pasteurizers. In order 
to reduce the cost of pasteurization to the minimum, it is 
essential that all steam turned into the pasteurizer be properly 
utilized. The pasteurizer, as well as the steam-pipes, should 
be properly insulated in order to prevent unnecessary conden- 
sation of steam. According to experiments carried on by 
Dr. Storch, all steam contains more or less air. By making 
a device on the pasteurizer for the escape of this air better 
results were obtained. By the use of such a vent it was made 
possible to heat 1890 pounds of water from 52° F. to 185° F., 
while without this air device, and with the same amount of 
heat, only 1467 pounds of water were heated. That is, by 
this device he made a gain of 30% in the heating efficiency 
of the pasteurizer. The contrivance used was simply a pipe 
attached to the bottom of the pasteurizer and extending down 
below the pasteurizer about 2 feet, then turned or bent, and 
brought up vertically a few inches above the bottom of the 
pasteurizer. The mouth of the pipe was then turned over. 
This pipe accomplishes two purposes. It removes condensed 
water from the pasteurizer, and also the accumulated air. It 
