44 
LABORATORY MANUAL 
(3) Allow the NaOH to dissolve, mix well and place at least 
20 cc. of the solution in a thoroughly cleaned graduated 
burette. 
(4) Measure out exactly 17.6 cc. of a prepared n /i 0 oxalic acid 
solution into a clean white cup. Add two drops of phenolph- 
talein indicator prepared according to F. & W. If 131. 
Titrate this against the NaOH solution in the burette. 
If exactly 17.6 cc. of NaOH solution produces a faint pink 
color, the NaOH solution is exactly n /i 0 . If more than 17.6 
cc. are required, it is too weak. If less is required, it is too 
strong. From the actual amount required, it is possible to 
calculate the amount of additional water or NaOH re¬ 
quired to make it the proper strength. 
B. To prepare an %<> Farrington alkali table solution. 
( 1 ) Measure out a definite quantity of distilled water into a 
clean bottle and calculate the number of Farrington alka¬ 
line tablets to add as follows: 
cc. water used X 25 
-= number of tablets necessary. 
97 
The rule for preparing an n /io solution is to use 25 tablets to 
97 cc. of water. 
Note: The Standard Farrington alkaline tablet solution 
is prepared by using 5 tablets to 97 cc. of water. An n /i 0 
Oxalic acid solution is prepared by weighing out 6.3 
grams of oxalic acid crystals (H 2 C 2 O 4 . 2 H 2 O) and add 
enough distilled water to make 1000 cc. 
Observations: 
Grams NaOH or 
cc. Water 
number of tablets 
NaOH solution 
Farrington’s 
Notes on preparation. 
Conclusion: 
Questions: (1) How should an n /i 0 KOH solution be prepared? 
(2) What is the strength of a Standard Farrington alkaline tablet 
Solution? 
(3) Explain in detail why 6.3 grams of C. P. oxalic acid crystals are 
used to make up an n / l0 solution? 
(4) Why is sulfuric acid not used for making n /i 0 solutions? 
References: F. & W. If 128-141, inclusive; Van S. 131-139; Jud. pp. 102- 
106; St. pp. 132-136. 
