~Effect of Varying Potassium Iodide.~--An excess of iodide is always
required to keep the iodine in solution; a larger excess has little
effect.
Iodide added -- 1 gram 20 grams
"Hypo" required 20.4 c.c. 20.5 c.c. 20.6 c.c.
The 20 c.c. of iodine used, itself contained 0.5 gram of potassium
iodide.
~Effect of Foreign Salts.~--
Bicarbonate of soda
added -- 0.5 gram 1.5 gram 5.0 grams
"Hypo" required 20.4 c.c. 18.2 c.c. 17.1 c.c. 16.0 c.c.
The solution obviously must be free from bicarbonate of soda. This
should be remembered, since when titrating arsenic assays with iodine it
must be present; and students must avoid confounding the two titrations.
In some other experiments, in which 10 grams each of the salts were
taken, the following results were obtained:--
Salt added -- AmCl AmNO_{3} Am_{2}SO_{4}
"Hypo" required 20.4 c.c. 20.5 c.c. 20.3 c.c. 20.2 c.c.
Salt added NaCl NaNO_{3} Na_{2}SO_{4}
"Hypo" required 20.3 c.c. 20.4 c.c. 20.4 c.c.
~Effect of Varying Iodine.~--
Iodine added 1.0 c.c. 10.0 c.c. 20.0 c.c. 50.0 c.c. 100.0 c.c.
"Hypo" required 1.3 " 10.2 " 20.4 " 51.0 " 102.0 "
~Determination of Dioxide in a Manganese Ore.
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