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To Test Prussian Blue

Pure ter, when cold, through coarse filtering paper; Prussian blue feels light in the hand; adheres add 1 ounce mucilage; boil for a few minutes, to the tongue; has a lively dark blue color, adding sufficient finely-powdered indigo and and gives a smooth deep trace. It should not lampblack to color it. Leave the mixture effervesce with acids, as when adulterated for 2 or 3 hours for the coarser particles to with chalk; nor become pasty with boiling subside; pour it off from the dregs, and bottle water, as when adulterated with starch. it for use.

Prussian blue, rendered inferior in its color by an admixture of free oxide of iron, may be improved by digestion in dilute sulphuric or muriatic acid, washing and drying. Its relative richness in the real ferroprussiate of iron may be estimated by the quantity of potash or soda which a given quantity of it requires to destroy its blue color.