Page:Encyclopædia Britannica, Ninth Edition, v. 19.djvu/98

Rh 88 P I K P I K commonly with alumina. Originally all lakes were red colours, the name being derived from the lac insect Coccus lacca, the colouring matter of which forms the lake now known as Lac Lake. But lakes of any colour or tint are now made. The most important lake pigment is Madder Lake, a compound of alumina and the tinctorial principle of madder root, Kulin officinalis, but now made with artificial alizarin. Scarlet or Carmine Lake has cochineal for its colour basis, and there are corresponding lakes from lac, kermcs, &c. Wood Lakes coloured with several of the red dycwoods have little durability, but they are nevertheless largely used by paper-stainers. C irminc, a colouring matter from cochineal, and Madder Carmine or Field s Carmine, from madder, arc exceedingly brilliant colours ; but the first of them is of a fugitive character. GREEN PIGMENTS form an extensive group embracing two sections: (1) simple greens, in which green is a primary inherent or natural colour ; and (2) compound greens, made up of intimate mixtures of blue and yellow pigments. The latter class it is obvious are capable of indefinite modification by simply varying the proportions of the compound ingredients. The following list embraces the principal commercial greens : Brunswick green, oxychloride of copper ; malachite green or mountain green, hydrated carbonate of copper ; verdigris, sub-acetate of copper ; verditer or Bremen green, hydrated oxide of copper ; Scheele s green, arsenite of copper ; Schweinfurt green, mixed acetate and arsenite of copper ; emerald green, a variety of Schweinfurt green ; mineral green, mixed copper oxide and arseuite ; chrome green, oxide of chromium ; Guignet green or veridian, hydrated oxide of chromium ; Cassel green, manganate of baryta ; cobalt green, oxides of cobalt and zinc ; ultramarine green, modified artificial ultramarine ; Veronese earth or terra verde, a form of ochre ; green lakes. The greater proportion of these greens are copper compounds the most brilliant of them containing also arsenic. They are all poisonous colours, the latter especially being dangerous poison ; and there can be no doubt that their free use in wall papers, the colour ing of toys, artificial flowers, &c., is frequently the source of dangerous disease and even death. Brunswick Green, the most important non-arsenical green, is an oxychloride of copper, but factitious Brunswick greens are not uncommon. Scheele s Green, the arsenite of copper, and Schu-einfurt Green, mixed arsenite and acetate of copper, are very powerful and brilliant colours. These copper greens all blacken in foul gases and when mixed with oil, and thus, although they possess great body, they are much more useful to the paper-stainer than the painter. The sesquioxide of chromium both water-free and hydrated, prepared in various ways, forms important stable green colours which resist atmospheric influences ; and chromium is further the basis of several other green colours, which, however, are not of importance. Cobalt Green, a mixed oxide of cobalt and zinc, discovered by the Swedish chemist liinman, is a valuable and durable but expensive colour. Cassel Green, called also RosenstiehVs Green, is a line innocuous pigment made by melting together sulphate of baryta and oxide of manganese, and carefully washing the resulting mass in water. Verona Green or Terra Verde, a natural celadon green highly valued by artists for permanence, is a mixed earthy body coloured by ferrous oxide, and Ultramarine Green, also a stable body, is an intermediate pro duct of the manufacture of ultramarine blue. BROWN PIGMENTS. Many of the painters browns are simply tints obtained by mixture. In the case of simple pigments the shades pass by fine gradations into yellows and reds, so that the limits of classification are not well defined. The following are generally classed as pure browns : umber, silicate of iron and man ganese ; brown ochres, called Mars brown, iron brown, &c., native and artificial earths ; Vandyke brown and Cologne or Cassel brown, peaty ochres ; purple brown, ferric oxide ; Spanish brown or tivcr, a brown iron ochre ; bistre, washed beechwood soot ; sepia, secre tion of cuttle-fish ; brown lake ; asphaltum, natural and artificial pitch. Iron and manganese, separately or combined, earthy or pure, are the sources of the principal brown pigments. Some of them are intermediate products between yellow ochres and red ochres by calcination of the yellow, and, as they are ochreous in their nature, their colours may be heightened or otherwise modified by calcining. Thus Umber, which properly is a hydrated silicate of manganese and iron, is brightened in colour by calcination into Burnt Umber. The finest umber comes from the island of Cyprus, and is known as Turkey umber. Large quantities also of &quot;English&quot; umber are mined in Devonshire and Cornwall. Real Vandyke Brown, a very celebrated pigment, ought to be a kind of bituminous peaty earth of a fine rich semi-transparent colour, allied to which are Cologne and Cassel Earth. But under the name Vandyke brown pure ferric oxide and ferruginous earths of a clear brown hue are also sold. Cappagh Brown is a peaty earth coloured by manganese, found at C appagh near Cork, Ireland, and is a valuable artists colour, as is also Bistre, a brown washed from the soot of beechwood. Sepia, a much valued warm brown, is a substance secreted by the cuttle fish, Sepia officinalis, which emits it to cloud the water for conceal ing its whereabouts when alarmed. BLACK PIGMENTS form a numerous class of bodies, though those in common use are easily enumerated. They appear in commerce principally under these names : vegetable black, carbonized vegetable matter ; lamp black, soot of oils and fats ; Indian ink, preparation of lampblack ; ivory black, carbonized ivory and bone ; bone black, carbonized bone ; blue black, washed wood charcoal ; charcoal black, carbonized wood ; black wad, a native oxide of manganese ; black lead, a form of carbon : tar, from distillation of organic substances. Most of these blacks owe their colour to carbon. From the charring of vegetable substances are prepared Charcoal Black, Blue Black, and Vegetable Black, but these take many names according as they are prepared from carbonized wood, twigs of the grape vine, peach and other fruit stones, cork, the lees of wine, &c. Bone and Ivory Blacks again are carbonized animal substances, principally bones, which when skilfully burned yield dense durable blacks. Lamp Black of the best quality is the soot deposited from the imperfect combustion of oils and fats, and the soots of resin and tar are also collected and used under this name. Indian Jnk (see vol. xiii. p. 80) is a form under which lamp black of the finest quality occupies an important position among pigments. Of the other blacks Tar is the most important owing to its extensive use as a preservative and antiseptic coating. Several pigments are prepared on account of special properties apart from the protective and decorative purposes for which ordinary paints are applied. Among such may be mentioned Balmain s luminous paint, a preparation in oil or water of certain of the phosphorescent sulphides. Objects coated with this material have the property of continuing to emit light in dark situations for some time after they have been exposed in daylight or to high artificial light. The luminous paint has been proposed for coating buoys, signals, public notice boards, clock and watch dials, playing balls, match boxes, &c. , but it has not come into extensive use. Powdered asbestos has been introduced as a fire-proof paint for wood ; but all common paints applied as distemper colour are equally fire-proof in the sense that they themselves are incombus tible, and when they coat wood thickly they offer great resistance to an incipient fire, and even retard combustion under very high heat. Numerous anti-fouling compositions for the painting of ships sides and bottoms and anti-corrosive, inoxidizable, damp-proof, and water-proof paints have been patented, some of which are in extensive use. ( J. PA. ) PIKE, freshwater fishes generally distributed over the rivers and lakes of Europe, northern Asia, and North America, and forming a small family (Esocidx) of Soft-rayed Fishes. They are readily recognized by their elongate compressed body covered with small scales, a long head, long and spatulate snout, and very large mouth armed with strong and long teeth in the jaws and broad bands of smaller teeth on the palate and tongue. The teeth point backwards or can be depressed so as to offer no obstruction to any object entering the gape, but prevent its withdrawal in the opposite direc tion. The dorsal and anal fins are placed far back on the European Pike (Esox lucius). tail, thus greatly increasing the propelling power of the fish, and, although pike are bad swimmers and lead rather a sedentary than a roving life, they are excelled by no other freshwater fish in rapidity of motion when, by a single stroke of the tail, they dash upon their prey or dart out of reach of danger. In the Old World one species only is known (E*ox lucius), which prefers lakes and sluggish reaches of rivers to strong currents or agitated waters. Its eastward range in northern Asia is not known ; it extends into Lapland in the north and into central Italy