Hydrochloric acid present 0.0 c.c. 1.0 c.c. 2.0 c.c. 5.0 c.c.
"Baric chloride" required 20.0 " 20.0 " 19.7 " 12.5 "
Nitric acid present 0.0 c.c. 1.0 c.c. 2.0 c.c. 5.0 c.c.
"Baric chloride" required 20.0 " 19.5 " 18.0 " 10.0 "
These show clearly the interference of free mineral acids, although very
dilute hydrochloric acid (1 c.c. in 500 of water) has no effect.
~Effect of Acetic and Citric Acids.~--A similar series of experiments
with these acids gave the following results:--
Acetic acid present 0.0 c.c. 5.0 c.c. 50.0 c.c. 100.0 c.c.
"Baric chloride" required 20.0 " 20.0 " 20.0 " 20.0 "
Citric acid present 0 gram 1 gram 5 grams
"Baric chloride" required 20.0 c.c. 20.0 c.c. 20.0 c.c.
These acids do not interfere.
~Effect of Sodic Acetate and Acetic Acid.~--In each of these experiments
5 c.c. of acetic acid was present.
Sodium acetate added 0 gram 1 gram 10 grams 50 grams
"Baric chloride" required 20.0 c.c. 20.0 c.c. 20.0 c.c. 20.0 c.c.
As sodic acetate and acetic acid did not interfere, it became desirable
to make some experiments on the _finishing point_. The first object
sought for was the smallest amount of the standard baric chloride in 500
c.c. of water, required to give an indication when tested in the manner
already described.
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