DAIRY HUSBANDRY 
43 
SERIES F. 
Acidity Determination of Dairy Products. 
Materials necessary for 10 students: 
30—Grams sodium hydroxide ( NaOH ). 
100 — cc. phenolphtalein solution ( indicator). 
1000—Farrington alkaline tablets. 
500 —cc.Vio normal oxalic acid solution {prepared by adding 500 
cc. of distilled water to 3.151 grams C. P. oxalic acid 
crystals {HiCfO\.2 H 2 0.) 
10—25 cc. pipettes. 
10—Small dippers {20 gauge shot gun shell size). 
5—5 gram weights. 
10 — 500-1000 cc. reagent bottles. 
5 — Kg. distilled water. 
EXERCISE NO. 32 
Object: To become acquainted with the preparation of a l /i 0 normal sodium 
hydroxide solution, and of a standard Farrington Alkaline Tablet 
Solution. 
Procedure: In preparing solutions for acidity testing, it is essential that 
there be a standard strength to work on. The standard 
adopted is the normal solution. 
A normal solution of an acid is one which, approximately 
speaking, contains 1.0 grams of replaceable hydrogen per liter 
of solution, and a normal solution of an alkali is one that will 
just neutralize a normal solution of an acid volume for volume. 
Another definition of a normal solution is as follows: A normal 
solution is one which contains the molecular weight of the ma¬ 
terial divided by the hydrogen equivalent of the active ele¬ 
ment, dissolved and diluted to a liter. Consequently a normal 
solution of an alkali is a solution that contains the chemical 
equivalent of 1.0 grams of replaceable hydrogen per liter. 
More accurate work can be done with weak solutions, hence 
it is customary to prepare n /i 0 solutions of an alkali for titrating 
the acidity of milk. 
A. To prepare a 1 /i 0 normal( n /i 0 )sodium hydroxide (NaOH) solution 
proceed as follows: 
(1) Carefully balance a clean dry stoppered test tube on an or¬ 
dinary butter or cheese moisture test scale. 
(2) Place a piece (2-4 grams) of NaOH in the test tube, stop¬ 
per tightly, and obtain the exact weight of the NaOH. 
Transfer the NaOH to a clean bottle. Calculate the vol¬ 
ume to which to dilute with distilled water to make an n /i 0 
solution as follows: 
grams NaOH X1000 
---= Total volume of solution 
4 
Rinse out the test tube into the bottle. 
