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Mars Marrone








Under the heading of a New Marrone Pigment there appeared some months
back in a chemical journal the following:--"The blood-red compound
obtained by adding a soluble sulphocyanide to a salt of iron in solution
can be made (apparently at least) to combine with resin thus: To a
concentrated solution of sesquichloride of iron and sulphocyanide of
potassium in ether, an etherial solution of common resin is added, and
the whole well shaken together. There is then mixed with it a
sufficiency of water to cause a precipitate, when it will be found,
after the mixture has stood a few hours, that the whole or nearly the
whole of the red-coloured iron compound has united with the precipitated
resin, forming the marrone-coloured pigment in question. When this
coloured substance is finely powdered and mixed with water, the liquid
is not the least coloured; whence it is inferred that the red iron
compound has chemically united itself with the resin."

The foregoing account is rather to be regarded as of scientific interest
than of practical utility. The blood-red solution of sulphocyanide of
iron is in itself not stable: when the red solution of this salt is so
exposed to the sun, that the rays pass through the glass jar containing
it, it is rendered colourless, but the colour is retained or restored
when the rays pass directly from the air into the fluid; so that when a
properly diluted solution is placed in a cylindrical glass vessel in
direct sunshine, it loses colour in the morning till about eleven in the
forenoon, when the rays beginning to fall upon the surface exposed to
the air, gradually restore the colour, which attains its maximum about
two o'clock. Moreover, the solution is immediately decolourised by
sulphuretted hydrogen and other deoxidizing agents, as well as by
alkalies and many acids. It is scarcely probable that the union of the
red colouring matter with the resin would suffice to secure it from
change; and there is little doubt that the new marrone pigment would be
a chameleon colour.

* * * * *

Failures in the process of burning carmines, and preparing the purple of
gold, frequently afford good marrones. Compounds more or less of that
hue are likewise furnished by copper, mercury, &c. Some ochres incline
to marrone when calcined: indeed we have remarked in many instances that
the action of fire anticipates the effects of long continued time; and
that several of the primary and secondary colours may, by different
degrees of burning, be converted into their analogous secondary,
tertiary, or semi-neutral colours.

The one marrone or brown-marrone pigment at present employed, brown
madder, is permanent.






TTITLE SEMI NEUTRAL GRAY

Of the tribe of semi-neutral colours, GRAY is third and last, being
nearest in relation to black. In its common acceptation, and that in
which we here use it, gray, as was observed in the third chapter,
denotes a class of cool cinereous colours faint of hue; whence we have
blue grays, olive grays, green grays, purple grays, and grays of all
hues, in which blue predominates; but no yellow or red grays, the
prevalence of such hues carrying the compounds into the classes of brown
and marrone, of which gray is the natural opposite. In this sense the





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Previous: Madder Marrone



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