Pitch And [greek: Kallos] Ornament The Blue Is Named Pittacal


The mode of separating pittacal has not been clearly described. Dumas

states, that when precipitated in a flocculent state from its solutions,

or obtained by evaporation, it closely resembles indigo, and, like it,

acquires a coppery hue when rubbed. It is inodorous, tasteless, and not

volatile; and is abundantly soluble in acetic acid, forming a red

liquid, which, when saturated by an alkali, becomes of a bright blue. It

> is represented as a more delicate test of acid and alkalis than litmus.

With acetate of lead, protochloride of tin, ammonio-sulphate of copper,

and acetate of alumina, it yields a fine blue colour with a tint of

violet, said not to be affected by air or light, and therefore

recommended for dyeing.

Like indigo, pittacal is believed to contain nitrogen, but its ultimate

composition has not been accurately determined. Dumas considers it

identical with a blue product obtained in 1827 from coal-tar by MM.

Barthe and Laurent. If this be the case, its greater stability over

coal-tar blues and colours generally admits of doubt. That, however, has

yet to be ascertained. Our object in noticing this blue has been

two-fold: first, to direct attention to wood-tar as a possible source of

colour; and secondly, to point to pittacal as a possible substitute for

indigo, possessing greater durability.