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- Browns And The Cold Semi-neutral Grays Marrone Is Practically To
- Black Chalk
- Also Called Scarlet Chrome Is A Bright Chromate Of Lead Of An
- Composition Chemical Analysis Has Shown Several Of The Blues To Be
- Burnt Verdigris
- Less Known As English Red Prussian Red And Scarlet Ochre True
- Olive In Dark Green; Russet And Citrine In Dark Orange The
- Belong The Dutch And Flemish Schools; The Sensible Which Aims At
- Known Likewise As Raw Sienna Earth Terra Di Sienna &c Is A
- Root Of The Anchusa Tinctoria Commonly Known As Alkanet A Plant

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- Pigment The [greek: Kinnabari] Of The Greeks And The Minium--a Term
- Pitch And [greek: Kallos] Ornament The Blue Is Named Pittacal
- Semi-neutral Gray Is Distinguished From The Neutral Grey Which
- White And Pure Black; The Grays Known To The Palette As Mineral Grey
- Rubric Lakes Or Field's Lakes Are Derived From The Root Of Rubia
- Bole Almagra Sil Atticum Terra Sinopica &c They Are Rather
- Principle Under The Name Of Wongshy And Consisting Of The
- Requires Its Contrast Orange In Equal Proportion Whether Of Surface
- So On The Palette Of Nature Each Colour Is An Example Of Colouring:
- Is In Reality We Grant That In Certain Objects Blue Is A Sign Of

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.





Next: Zinc-cobalt Blue
Previous: Wood-tar Blue

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