COLORADO EXPERIMENT STATION 
7 
the color and body of the test appears to be uniform. The bottles may 
then be let stand from one to three minutes, given another gentle, 
rotary motion, and they are then ready for the tester. 
Whirling .—The test bottles, with the acid and milk properly 
mixed, are now placed in the tester. 
The bottles should be arranged in pairs at opposite sides of the 
center so that they will balance when rotating. 
First, whirl four minutes, at speed of machine indicated on the 
cover, then fill with soft, hot water to the bottom of the neck and 
whirl two minutes, fill the neck of the bottle with hot water of 170 
degrees F. to within two or three per cent of the top, and whirl 
one minute. The periods of whirling given means the time during 
which the tester is run at full speed and does not include the time 
of starting and stopping. 
Reading the Tests .—Milk tests should be read at a temperature 
between 120 degrees and 130 degrees F. This temperature may be 
best obtained by use of a five minute hot water bath before reading. 
In reading the tests, hold the bottles perpendicular and on a 
level with the eye. Place one point of the dividers at the lower end 
of the fat column and the other point at the top of the 
meniscus or upper curved surface of the fat column. 
Then lower the dividers until the lower point 
is on the zero mark of the test bottle, the upper point 
will indicate the per cent of fat. Care must be taken 
to hold the dividers rigid while lowering. 
The following are a few precautions in making milk 
tests: 
1. Always make tests in duplicate. 
2. Make sure that the sample is a representative one. 
3. Have the temperature of the milk and acid at 
65 degrees to 70 degrees F. before mixing. 
4. Use only acid of right strength, specifc gravity 
1.82 to 1.83. 
5. Mix milk and acid thoroughly as soon as acid is 
added, by gentle rotary motion. 
6. Mix a second time after a short interval. 
7. Make'sure that tester does not jar. Showing 
8. Set bottles in water of 120 to 130 degrees F. five SSmtobe 
minutes before reading. test^A-ToB 
9. Read each test twice to make sure no mistakes have been 
marie. 
a—= 
.id 
Testing Skim Milk 
The following changes should be made in testing skim milk from 
methods used in testing whole milk: 
Skim milk bottles must be used; these bottles are graduated to be 
read to one one-hundredth of one per cent. More acid is needed than 
