_Reagents._—1. Nitric acid. Dilute concentrated nitric acid with an
equal volume of distilled water. Free the diluted acid from brown oxides
of nitrogen by aeration.
2. Silver nitrate. Dissolve 20 grams of silver nitrate in 1 liter of
distilled water.
3. Standard manganous sulfate. Dissolve 0.288 gram of purest potassium
permanganate in about 100 cc. of distilled water. Acidify the solution
with sulfuric acid and heat to boiling. Add slowly a sufficient quantity
of dilute solution of oxalic acid to discharge the color. Cool and
dilute to 1 liter. One cc. of this solution contains 0.1 mg. of
manganese.