DAIRY HUSBANDRY 
47 
EXERCISE NO. 34 
Object: 7 o compare Mann’s and theFarrington Alkaline Tablet acidity tests. 
Procedure: A Standard Farrington Alkaline tablet solution is prepared 
by dissolving 5 tablets in 97 cc. of water. The strength of this 
solution should be such that if an 18 gram (17.6 cc.) sample of 
milk is used, 1 cc. of the solution will indicate exactly .01% 
acidity. If 97 cc. of the solution were necessary to produce a 
faint pink color in an 18 gram sample, there would then be 
present .97% lactic acid or 18X.0097 =.1746grams of lactic 
acid would be present in the 18 gram sample. Since 5 tablets 
were used in preparing the 97 cc. each tablet will neutralize 
.1746 -T- 5 = .03492 grams of lactic acid. Since there is one 
tablet in 19.4 cc. of water, each cc. of the Standard solution 
will neutralize .0018 grams of lactic acid. Therefore .0018 -5- 
.09 = .02 = 2 /ioo or the solution is 1 / 60 normal. This illustration 
shows how it is possible to prepare a solution of any desired 
strength. 
A. Use any of the three methods outlined in Exercise 33, Series F, 
and test in duplicate by the Mann’s test each of the lots of 
milk provided. 
B. With a pipette measure out 17.6 cc. of the milk to be tested 
into a white cup. Use a 100 cc. graduate containing the 
Standard Farrington Alkaline tablet solution, and continue add¬ 
ing small quantities of the solution to the milk until a faint 
pink color develops. Record the number of cc. of the solution 
used. The milk in the cup should be stirred continuously while 
the Farrington alkaline tablet solution is being added. 
C. Test each of the lots of milk provided by both of the above 
methods. All tests should be made in duplicate. 
Observations: 
Test 
cc. sample 
cc. solution 
% acidity 
Mann’s 
a 
b 
Farrington’s 
a 
b 
Conclusions: 
Questions: (1) What are the advantages and disadvantages of the Far¬ 
rington Alkaline tablet solution and the NaOH solutions? 
(2) What influence has the richness of cream on the acidity test? 
(3) If a 40% fat cream contains .20% acidity, what is the acidity 
of the serum? 
(4) If cream testing 25% fat has an acidity of .5%, what will be the 
“corresponding” acidity of cream testing 40% fat? 
References: F. & W. If 135-151, inclusive; Van S. pp. 131-151; Jud. pp. 
102-111; St. pp. 132-136. 
