Heat potassium chloride specified in
JIS K 8121 at 110 ºC ± 2 ºC for about 2 hours, let it stand to cool in a desiccator, and
then weigh 3.166 g into a weighing dish. Dissolve in a small amount of water, transfer
to a 1,000-mL volumetric flask, and add water up to the marked line