PAINTING MATERIALS
Para Red or Para Toner was one of the early synthetic diazo dyes tuff colors;
it is ^-nitrobenzene-azo-/3-naphthol, CisHnNsOa, and is derived from the dye
intermediate, paranitraniline (Colour Index, p. n). For pigment purposes, the dye
is usually precipitated on barytes. It is brilliant in hue, but darkens on exposure
to strong light and sometimes becomes brown; it has a tendency to bleed in oil
paints. Although Para red was formerly widely used in the manufacture of red
paints and enamels, it has been replaced in recent years by the more stable Lithol
Red and Toluidine Red. Para red has perhaps never been offered to the artists'
trade under this name, but it has no doubt occurred in pigments as a toner and
substitute in cheaper lines of paints. It was first made by Messrs Holliday and
Sons in England in 1880 ( Colour Index, p. n).
Paris Blue (see Prussian Blue).
Paris Green (see Emerald Green).
Permanent Blue is a name used by some artists' colormen for ultramarine (see
Ultramarine Blue, artificial). It is occasionally given to a pale variety of that
pigment.
Permanent Green is a name sometimes applied by artists' colormen to mix-
tures of viridian with a yellow pigment like cadmium yellow or zinc yellow; it may
also contain zinc oxide.
Permanent Violet (see Manganese Violet).
Permanent White (see Barium White).
Persian Berries Lake (yellow berries, buckthorn berries) is a yellow lake made
from the dried, unripe berries of various shrubs of the buckthorn family, Rhamnus,
found in the Near East and now imported from Smyrna and Aleppo ( Colour Index,
p. 293). The berries are also available from European members of the family.
The coloring principle is rhamnetin, CieH^O?, which is extracted by boiling water.
The lake is made by the addition of alum, followed by soda (op. cit., p. 301; see
also Perkin and Everest, p. 628). Other colors are produced with other mordants.
It is insoluble in water and in alcohol but is soluble in alkalis, forming a yellowish
brown solution; it is decomposed and decolorized by mineral acids, but is moder-
ately stable in light. Colors of this origin were popular in France and in England
in the XVIII century (Thompson, The Materials of Medieval Painting, p. 187),
but are no longer current.
Phosphotungstic Acid Bases are complex compounds of phosphorous pen-
toxide and tungstic acid combined approximately in the ratio, iP^Os: i^WOa.
These bases are now quite extensively employed with organic dyestuffs in making
lake pigments and toners of excellent strength and light-fastness. They were de-
veloped in Germany, and it appears that first patents were issued to the Badische
Anilin und Soda Fabrik (see British patent 15,951, 1914; French patent 474,706,
1914; also British patent 216,486, 1924).
Phthalocyaoine Blue CMonastraP blue) or copper phthalocyanine,
is an organic blue dyestuff that was recently developed by chemists