56 
LABORATORY MANUAL 
EXERCISE NO. 41 
(42 should be substituted at this point if the ether extraction test is to 
be made.) 
Object: To become acquainted with the salt test of butter. 
Procedure: In the average creamery where one man performs many 
duties, it is customary to make but one or two tests of butter; 
always the moisture and occasionally the salt test. It is as¬ 
sumed that average butter contains 1% of curd, hence the fat 
content of the butter is approximated by difference as follows: 
100—(% moisture + % salt -f 1) = % fat. 
A. If the moisture test has been made or if the ether extraction 
test (Exercise 42) has been made, the residue is used for the 
salt test. If neither has been made the sample is obtained 
and weighed out as for the moisture test. 
B. The fat, curd and salt mixture is transferred to a pint jar or 
bottle with 250 cc. of warm (110° F.) water, measured out in a 
250 cc. volumetric flask. Mix thoroughly with a rotary motion 
and allow a few seconds for the fat to rise. 
C. Transfer 17.6 cc. of the mixture to a white cup. Hold finger 
over upper end of pipette while it is being inserted to prevent 
the entrance of fat. 
D. Add two drops of potassium chromate indicator and titrate 
with the prepared silver nitrate solution. 1 cc. of the solution 
indicates 1% salt. 
Observations: 
Sample 
Weight 
cc. Ag No 3 Solution 
% Salt 
1 
2 
Conclusions: 
Questions: (1) Give the chemical reactions taking place in the salt test. 
Use equations. 
(2) Why should the silver nitrate solution be kept in brown glass 
bottles? 
(3) What is the purpose of adding salt to butter? 
(4) Why does the amount of salt that can be incorporated in butter 
depend upon the moisture content of the butter? 
References: F. & W. ^ 278; Van S. pp. 125-130. 
