3. Potassium oxalate. A 2 per cent solution.

4. Manganous sulfate. Dissolve 480 grams of the salt in water and dilute

the solution to 1 liter.

5. Alkaline potassium iodide. Dissolve 700 grams of potassium hydroxide

and 150 grams of potassium iodide in water and dilute the solution to 1

liter.