DAIRY HUSBANDRY 
EXERCISE NO. 17 
Object: To become, acquainted with the Rose-Gottlieb method for the de¬ 
termination of fat in milk. 
Procedure: The Mojonnier tester, largely used in milk condensing fac¬ 
tories and ice cream factories, is based on the Rose-Gottlieb. 
A. Make a duplicate test of the milk, provided, by the Babcock test. 
B. Pipette 10 grams of the milk provided into a specially con¬ 
structed Rohrig extraction tube, and proceed as follows: 
(1) Add 1 cc. of concentrated ammonia and mix thoroughly. 
(2) Add 10 cc. of 92% ethyl alcohol and mix thoroughly. 
(3) Add 25 cc. of washed ethyl ether and mix thoroughly. 
(4) Add 25 cc. of petroleum ether and mix thoroughly. 
(5) close the tube with a moist stopper and allow to stand for 
6 hours. 
(6) Read at the base of the clear liquid and at the top and 
drain off an aliquot portion of the clear liquid into a clean 
carefully weighed aluminum evaporating dish. 
(7) Evaporate the ether from the dish under a hood, until all 
ether has evaporated. Cool the dish and carefully weigh 
again. The increase in wieght represents the fat in that 
portion of the solution drawn off. The total weight of the 
fat can be calculated and since a 10 gram sample of milk 
was used, it is easy to determine the per cent of fat present. 
Note: The temperature of the hot plate should be in the 
neighborhood of 135° C. (275°F.). 
Observations: 
Sample 
Grams 
milk 
% of ether 
solution 
used 
Weight of 
empty dish 
Weight of 
contents after 
evaporation 
Amt. 
of fat 
present 
1 
a 
b 
2 
a 
b 
Conclusions: 
Questions: (1) How would the Rose-Gottlieb procedure differ, if a sub¬ 
stance high in fat were tested? 
(2) If a patron delivers 525 pounds of milk testing 3.8% and the 
price of butter fat were 42c, what would he receive for the 
milk? 
(3) If the farmer in problem 2 were paid at the rate of 1.80 for 
100 pounds of 3.5% milk and 5c for each .1% above or below 
this test, what would he receive for the milk? 
(4) What would he get for the milk at the rate of $1.50 per 10 gal¬ 
lon can? 
References: F. & W. If 254; Van S. 253-254. 
