Prussian Black

: ON THE NEUTRAL, BLACK.

The same Prussian blue which gives a brown when burnt in the open air,

yields a black when calcined in a close crucible. Very intense, very

soft and velvety, and very agreeable to work, this bluish-black dries

much more promptly than most other blacks, and scarcely requires

grinding. On account of its extreme division, however, it would probably

be found more energetic as a decolourising agent in admixture with

organic pigments than most carbonaceous blacks.



Another Prussian black, containing copper, and made by a wet process, is

obtained when a dilute solution of cupric sulphate and ferrous sulphate,

in proper proportions, is mixed with a quantity of ferrocyanide of

potassium not in excess. A very bulky deep black precipitate is formed,

which is difficult to wash, and is deep black when dry. It is insoluble

in water, and appears to be a compound analogous to Prussian blue. As a

pigment, this black is inferior to the preceding.



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