COOLING, STORING, AND SHIPPING MILK. 21 
of ice into the tank and using a thermometer to ascertain the tem- 
perature to which the milk is cooled. When milk is precooled by 
means of a surface cooler to between 52° and 62° F. and is placed 
in a cooling tank in which the temperature of the water is 45° F., 
from 14 to 2 pounds of ice for each gallon is necessary to cool milk 
to and to keep it at 50° F. for a day. When precooling is not prac- 
ticed and the tank water has a temperature of 45° F. about 4 pounds 
of ice per gallon will be necessary. 
EFFICIENCY OF DIFFERENT TYPES OF CANS FOR HOLDING 
MILK. 
In order to determine the relative value of different types of milk 
cans for maintaining low temperatures in milk held without agitation 
for a considerable period, a series of experiments was conducted. Six 
10-gallon cans were used, as follows: Nos. 1 and 2 were insulated; No. 
3 had an ice compartment; No. 4 was an ordinary can covered with 
1-inch felt jacket; No. 5 was an ordinary can covered with a 4-inch 
jacket; and No. 6 was an ordinary milk can. The cans were placed 
in a room in which the temperature was maintained at 744° F. 
The initial temperature of the milk in cans Nos. 1, 2, 3, and 4 was 
35° F.; in No. 5 it was 36° F., and in No. 6 it was 37° F.—The milk 
was not stirred in any of the cans during the test, the temperature 
reading being taken by removing the top and inserting a long- 
stemmed thermometer into the center of the can. In each case for- 
maldehyde enough was added to the milk to prevent premature 
souring. 
The results of the test are shown in figure 16. It will be noted that 
the time required for the temperature of the milk to rise to 50° F. 
was as follows: 
Hours. Hours. 
vm INON PSE ire EE Ae th UE i isso ADMIN Os eT Paps 
GREW O UNS Coy alba tn On| SCAN Vokes sh aa ea ok Me 18 
NT NO ee ET STS Sag NSD a NTE Pl OAT INO Gis ees SE See 11 
It should be kept in mind of course that the initial temperature of 
the milk in can No. 5 was 36° F. and in can No. 6 37° F. Comparing 
the various cans with No. 6 (the bare, unprotected can) it will be 
neted that No. 1 took 2.18 times as long; No. 2 required 2.73 times as 
long; Nos. 3 and 4 required twice as long; and No. 5 required 1.63 
times as long as No. 6 for the temperature of the milk to rise to 50° 
¥’. The results indicate the efficiency of the various methods of pro- 
tecting cans in keeping milk at low temperatures. 
In test No. 2 the conditions were similar to those in the first test 
except that the room temperature was 99.5° F’., or 25 degrees higher, 
and the initial temperature of the milk in each can was 44°. F. The 
