It is prepared by treating aniline oils successively with nitrous
acid and arsenic acid, and one of an alkaline nitrate at about 212°
Fah., for a short time. The product is extracted with boiling water,
neutralized with an alkali filtered, and the color precipitated with
common salt.
Pure hydrochloride forms thin reddish crystals, which are soluble
in water and in alcohol, yielding a yellowish red solution. The
most characteristic reaction of safranine is that when concentrated
sulphuric acid is gradually added to its solution, the color changes to
violet, then to blue, dark green and light green. Then, on diluting the
solution with water, the same changes of color take place, only in the
reverse order.
In feather dyeing safranine is used chiefly in making light colors of
a pinkish hue; such as pink, terra cotta, and to give a tint to ecru,
beige and such colors.