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Called When Levigated Body White Is An English White Lead In The








form of scales or plates, sometimes grey on the surface. It takes its
name from its figure, is occasionally equal to Crems white in colour,
and generally surpasses in body all other white leads. In composition,
it is a mixture of protocarbonate and hydrated oxide of lead, the latter
decreasing the opacity of the product according to the greater
proportion in which it is present.

TTITLE FLEMISH WHITE, OR SULPHATE OF LEAD

Is an exceedingly white precipitate from any solution of lead by
sulphuric acid, much resembling the blanc d'argent. It is inferior,
however, both in body and permanence to the ordinary carbonate. Hence,
white lead which has more or less been converted by sulphuretted
hydrogen into sulphide, and again been converted into sulphate by
oxidation, with a view to restoring its colour, becomes peculiarly
liable to the influence of impure air.

TTITLE LONDON AND NOTTINGHAM WHITES.

The best of these do not essentially differ from each other, nor from
the white leads of other manufactories. The latter variety, being
prepared from flake white, is usually the greyer of the two.

TTITLE PATTISON'S WHITE, OR OXYCHLORIDE OF LEAD

Is a mixture of chloride and oxide of lead, formed by precipitating a
solution of chloride of lead with soda, potash, lime, or baryta, in the
caustic or hydrated state. It would appear that when the oxychloride is
used as a paint, the oxide contained in it gives rise to an oleate of
lead, and, in consequence of this saponaceous matter, is capable of
spreading over an extended surface. The product has been described as
possessing properties which are superior to those of white lead,
inasmuch as it does not so readily blacken as the latter body. Dr. Ure,
however, found that water removes the chloride of lead from the paint
compounded of this article, and, consequently, that it is not so
effectual as the carbonate. As an artist's pigment, a partially soluble
compound of lead can decidedly not be eligible.

TTITLE ROMAN WHITE

Is of the purest white colour, and differs only from blanc d'argent in
the warm flesh tint of the external surface of the large square masses
in which it is commonly prepared.

Besides the foregoing, there are other white leads, generally foreign,
cheaper, and adulterated. Many of these are mixed with a small quantity
of charcoal, indigo, or Prussian blue, so that the dead yellowish shade
which they present may be enlivened to a brighter hue. Among them may be
named--

TTITLE CERUSE.

A French variety, not necessarily, but not unfrequently, mixed with
different chalky earths in various proportions; and the following
Belgian kinds:

TTITLE DUTCH WHITE,

Containing three fourths of sulphate of baryta.

TTITLE HAMBURGH WHITE.

A mixture of two parts of heavy spar and one of the plumbous compound.

TTITLE KREMSER WHITE,

Differing from the rest in being unadulterated.

TTITLE VENETIAN WHITE

Composed of heavy spar and the carbonate in equal proportions.


ZINC WHITES.

TTITLE CHINESE WHITE.

The introduction, in 1834, of this peculiar preparation of oxide of zinc
has proved an incalculable boon to water-colour painters, who formerly
had no white which combined perfect permanency with good body in
working. Its invention obviated the necessity for using white lead, a
pigment which, though it may be employed with comparative safety in oil,
is quite unfitted for water. Since the period of its production, Chinese
white has been generally preferred by water-colour artists, as being the
most eligible in their peculiar department. Previous to that period, the
complaints of whites changing were of constant occurrence; but in no
instance has any picture, in which this white has been used, suffered
from its employment. To the colour of oxide of zinc, sulphuretted
hydrogen is altogether harmless; sulphide of zinc being itself white.
The variety under notice works and washes well, possesses no pasty or
clogging properties, and is prepared beautifully white. Moreover, it has
the desirable quality of dense body; so much so, that, as the painter
works, his effects remain unaltered by the drying of the colour. It may
likewise be safely mixed with all other pigments, the following blending
very satisfactorily with the white for opaque lights--cadmium yellow,
orange, and red; gamboge; aureolin; yellow ochre; vermilion; and light
red. Without the artistic drawbacks of constant white or the chemical
defects of white lead, and retaining the advantages of both, Chinese
white cannot but be considered as a most important addition. It is a
matter of regret that this pigment is not equally efficacious in oil.

TTITLE ZINC WHITE

Is either the anhydrous oxide, the hydrate oxide, or hydrated basic
carbonate of zinc. It varies in opacity and colour according to the mode
of manufacture, and the purity of the compound, but may always be relied
upon as permanent. The whiteness of the best samples rivals that of
white lead, and it is not tarnished like the latter by sulphurous
vapours. In opacity it never equals white lead, and might perhaps serve
advantageously as a glaze over that pigment, either alone or compounded
with other colours; as well as act as a medium of interposition between
white lead and those colours which are injured by it, such as gamboge,
crimson lake, &c. When duly and skilfully prepared the colour and body
of this pigment are sufficient to qualify it for a general use upon the
palette in oil: in water it has been superseded by Chinese white.

Occasionally, starch, chalk, white clay, and carbonate of baryta, are
employed as adulterants; none of which, however, are inimical to
stability.

As a pigment, zinc white may be said to be innoxious. As oxide of zinc
does not readily form a saponaceous compound with fats or oil like white
lead, the paint prepared with it and ordinary linseed oil does not dry
or harden so rapidly. For the purpose of causing it to be more
siccative, the oil was boiled with a large quantity of litharge, but by
this method the white was liable to tarnish on meeting with foul air.
Instead of litharge, experiments have led to the choice of salts of
zinc, such as the chloride or sulphate, a small percentage of which, on
being mixed with the oil or oxide, confers upon it the property of
rapidly hardening. The same result is attained by employing an oil,
dried by boiling with about five per cent of peroxide of manganese. In
either case, a paint retaining its white colour permanently is produced.
These agents might, with advantage, be more generally used in the place
of litharge for rendering oils siccative. Many pigments which are not
naturally affected by sulphurous emanations are apt to suffer if mixed
with an oil made drying by means of lead.

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