Yes, I am; it is much used in painting, both in oil and in water colours; but it is not reckoned a permanent oil-colour.
MRS. B.
That defect arises, I believe, in general, from its being badly prepared, which is the case when the iron is not so fully oxydated as to form a red oxyd. For a solution of green oxyd of iron (in which the metal is more slightly oxydated), makes only a pale green, or even a white precipitate, with prussiat of potash; and this gradually changes to blue by being exposed to the air, as I can immediately show you.
CAROLINE.
It already begins to assume a pale blue colour. But how does the air produce this change?
MRS. B.
By oxydating the iron more perfectly. If we pour some nitrous acid on it, the prussian blue colour will be immediately produced, as the acid will yield its oxygen to the precipitate, and fully saturate it with this principle, as you shall see.
CAROLINE.
It is very curious to see a colour change so instantaneously.
MRS. B.