methyl group (CH,) generally increases the violet tendency; the phenyl group (CH) produces bluish tints; the naphthyl group (CH) a tendency toward brown-red, etc. The relative position of the groups likewise plays a large part in the determination of color. But, as we have already observed, a definite and all-embracing rule does not exist. Frequently compounds must enter into combination with a base or an acid before they will fix themselves upon the fibre, and then the tints are frequently affected by the different bases or acids to a varying degree. For example, alizarin dyes red with the hydroxide of aluminum, and black with the hy droxide of iron.

For the purposes of the present sketch, the coal-tar colors may be grouped in five classes: viz. the azo-colors; triphenyl-carbinol derivatives; quinone derivatives; diphenyl-amine derivatives; and indigo dyes.

Azo-COLORS. The characteristic compound of this class is azo-benzene, C.H,N = NCH, al ready mentioned above. We have seen that the introduction of either NH, or OH in place of a hydrogen atom produces a coloring matter-yellow in the former, orange in the latter instance. Replacing either or both of the phenyl groups (CH) by more complex hydrocarbon groups deepens the tone (with a tendency toward the redder tints), increases the affinity for fibres, and diminishes the liability to fade. The earlier dyes of this class, such as 'aniline yellow,' 'Bismarck brown,' chrysoidin, etc., were singularly brilliant, but were not fast; whereas the browns and the many reds, ranging from scarlet to purple, which are now produced under the names of ponceaux or bordeaux, congos, quinoline red, etc., are exceedingly permanent. In manufacturing this class of dyes, nitrous acid is allowed to act upon an ice-cold solution of the salt of any primary base (like aniline), and the 'diazo-salt' formed is allowed to act on another base or a phenol; an endless variety of combinations is thus possible.

TRIPHENYL-CARBINOL DERIVATIVES. These represent the first discoveries in the aniline dyes, and some of them are still produced on the larg est possible scale. The fundamental compound of the class is triphenyl-carbinol (CH),COH, and its derivatives are properly subdivided into rosanilines, rosolic acids, and phthaleïns.

In the rosaniline group. two or three amidogroups (NH2) are introduced in place of hydrogen atoms of the phenyls (C,H,). The di-amidocompounds are green; the tri-amido-compounds are red, violet, or blue. Strictly speaking, the compounds thus obtained are not themselves dyes, but are bases which must first be combined with suitable acids, and thus brought into a soluble form. Their salts are beautifully crystalline bodies in the solid condition, showing colors quite different from those of the solutions, and having peculiar lustres like those of beetles' wings. The solutions have very intense colorations and stain animal fibres readily and permanently, although they do not fix themselves easily upon cotton or linen. They are the most brilliant and lively dyes, but are strongly affected by sunlight, and are consequently less useful than some dyes of other classes. They are generally manufactured by oxidizing processes at a comparatively high temperature, whereby two or three simpler compounds are welded, as it

VOL. V.-6.

were, into compounds of complex molecular structure. Thus, in the manufacture of the wellknown magenta dye (a tri-amido-compound) approximately equal quantities of aniline, orthotoluidine, and para-toluidine are heated from 8 to 10 hours with arsenic oxide to 190° C., in large iron kettles. A very thick mass results, which can be extracted with hot water, and the compound thus obtained is found to be made up of molecular quantities of aniline, ortho-toluidine, and para-toluidine, chemically combined.

Rosolic acid and its derivatives are made by the condensation of various phenols, three phenols being condensed into one compound of the rosolic acid group, just as three bases are condensed into one compound of the rosaniline group. The comparatively few dyes of this group give various shades of red. The hydroxyl groups, and hence the acid character of the phenols, remain unchanged in the products of condensation; the latter therefore combine with bases, and then they readily go into solution.

The phthaleïns differ from the rosolic acids in so far as one of the three phenyls of the triphenyl-carbinol is connected in them with a carboxyl group (COOH), the other two phenyls having one or more hydroxyls apiece, as in the rosolic acids. The phthaleïns were discovered by Adolph Baeyer, and are chiefly remarkable for the fluorescence of their alkali salts in solution. They are prepared by heating phenols with phthalic anhydride and a little sulphuric acid; when resorcin is taken as the phenol, a very well-known compound is obtained, which has been called fluoresceïn, while its sodium salt is known as uranin. Solutions of the latter are yellow by transmitted light, but bright green by reflected light. This fluorescence is so intense that it is distinctly noticeable in extremely dilute solutions; so that this salt has been used to trace subterranean watercourses supposed to connect two neighboring bodies of water, the dye being thrown into one of these and fluorescence being subsequently noticed in the other. potassium salt of a brominated fluorescein is eosin, CH,O,Bг.K2, with a magnificent red and yellow fluorescence. These fluorescences disappear on the fibre, but eosin and analogous substances impart very brilliant flesh-tints to silk and wool.

The

THE QUINONE DERIVATIVES. These contain the characteristic nucleus

and are almost invariably colored, although they become suitable for dyes only when they also contain several hydroxyl groups. By far the most important substance of this class is alizarin (q.v.), which was already mentioned as identical with the active principle of madder. Anthracene (q.v.), a coal-tar hydrocarbon, is converted into anthraquinone by heating with potassium bichromate and sulphuric acid; the anthraquinone is acted upon by fuming sulphuric

acid, and the resulting compound is melted with caustic soda, yielding a sodium salt of alizarin. This is soluble in water with a fine red color, but does not fasten upon any kind of fibre. If, how ever, cotton is previously impregnated with salts of aluminum, iron, or chromium, the alizarin will form insoluble salts ('lakes') with these metals; and as the precipitation occurs within the pores of the fibre, subsequent washing cannot remove it. Colors of this class of dyes are not suitable for silk and wool, but are very intense and permanent when properly applied to cotton.

THE DIPHENYL-AMINE DERIVATIVES. These include many varieties of dyes, such as the indulins, indophenols, thiagins, etc. Their chemistry is too involved to be disposed of in a few words. It may, however, be mentioned that their characteristic groups are similar to anthraquinone, excepting that the oxygen of the latter is replaced by sulphur, imido-groups, etc. The more important dyes of this class include 'methylene blue' and 'aniline black.'

INDIGO DYES. By far the most important of these is indigo itself, a vegetable dye obtained from a tropical plant cultivated in India since the earliest times. The sap of this plant, when fermented under conditions excluding oxygen, yields indigo white, a soluble material having the formula C1HN2O2; if the fermentation proceeds in the open air, indigo blue, CH10NO2, is produced. This substance is a derivative of the base called indol, C,H,N, which occurs ready formed, in small quantities, in many animal and vegetable secretions. It can be prepared artificially from aniline and chloraldehyde. When

indigo was found to consist of two indol molecules joined together and oxidized, the clue for the production of artificial indigo was at hand. It has since been found that any benzene derivative having a nitrogenous group and a twocarbon group in the 'ortho' position may give rise to the formation of indigo. The first practical method, devised by Baeyer in 1880, involved the action of potassium hydroxide on orthonitropropiolic acid; but many other methods have been devised since then, such as the action of melted potassium hydroxide on bromacetanilid, the action of halogenated acetone on aniline, etc. Indigo is one of the most reliable dyestuffs, both as to brilliancy and permanency, and there is little difference in these respects between the natural and artificial products. The finished compound can, however, only be applied after reduction to the soluble indigo-white, and this makes its use in dyeing and printing somewhat cumbersome. In some of the methods for preparing artificial indigo, the fibre can be impregnated with one ingredient and the other applied either in the dye-vat or from the printing rolls; consequently, indigo can be and is often directly prepared in the quantities and in the places in which it is needed. See INDIGO.

LIST OF COLORS. The following are some of the best known commercial coal-tar colors, their molecular formulas, and the principal methods employed in their manufacture.

Aldehyde Green.-See Aniline Green below. Aniline Black, CH2N3, made by the oxidation of aniline with mineral salts.

Aniline Blue (triphenyl- rosaniline hydrochloride), CHNCI, made by heating rosaniline, benzoic acid, and aniline, and subsequently adding hydrochloric acid.

Aniline Brown, Bismarck Brown, or Phenylene Brown (triamido-azobenzene), C12H1N, made by the action of nitrous acid on metaphenylenediamine.

Aniline Green, or Aldehyde Green, C2HNS2O, made by the action of ordinary aldehyde on an acid solution of rosaniline sulphate and the subsequent addition of sodium hyposulphite.

Aniline Orange. This name is applied to various compounds made by the action of amidosulphonic acids on phenols. The name is often applied to the so-called Victoria Orange, CH.NO.

Aniline Red.-See Fuchsin below.

Aniline Scarlet, C1H1N2O,SNa, made by the action of diazoxylene on naphthosulphonic acid. Aniline Violet.-See Mauveïn below.

Aniline Yellow (hydrochloride), C12H12N,Cl, made by the action of nitrous acid on an excess of aniline.

Alizarin, CH,O,, made artificially by successive treatments of anthracene with chromic acid and fuming sulphuric acid, and melting the product with potassium hydroxide. Among the dyes allied to alizarin are: Alizarin Black, CHO,.NaHSO,; Alizarin Blue, C,H,NO,; Alizarin Orange, C1H,NO.; and Alizarin Violet, or Galleïn, C20H1007.

Auramin (hydrochloride), C1H2N ̧OC], made by the successive action of phosgene gas (carbon oxychloride) and ammonia upon dimethyl-aniline.

Aurantia (ammonium salt of hexanitro-diphenylamine), CH,NO12.NH,, made by the action of nitric acid on methyl-diphenylamine.

Aurin, CHO,, made by the action of oxalic and sulphuric acids on phenol. Benzaldehyde Green.-See Malachite Green be

low.

Benzidine Red.-See Congo Red below.

Benzopurpurins, dyes of various scarlet shades. They are chemically allied to Congo Red (which see below), and are made by treating salts of toluidine (which is made from nitrotoluene, and is analogous to benzidine) with nitrous acid, and combining the resulting salts with a- and B-naphthylamine sulphonic acids.

Bismarck Brown.-See Aniline Brown above. Blackley Blue.-See Indulin below. Bordeaux.-See Ponceaux below. Chrysoïdin (hydrochloride), C12H1N,Cl, made by the action of diazo-benzene chloride on metaphenylene diamine in aqueous solution.

Congo Red, or Benzidine Red, CHNS2O,Na2 made by the action of nitrous acid and then of sodium naphthionate on benzidine hydrochloride.

Eosin, CH,O,BгK2, or СHOBг,Na2, made by the action of bromine on fluoresceïn.

Erythrosin, CH,O,I,Na2, made by the action of iodine on fluoresceïn.

Fluorescein, C20H12O5, made by the action of phthalic acid anhydride on resorcin.

Fuchsin, Rosaniline Hydrochloride, Magenta, or Aniline Red, CHNCI, made by the oxidation of toluidine and aniline in the presence of acids. Galleïn.-See Alizarin above. Helianthin.-See Methyl Orange below. Indigo. See text of the article above. Indulin, or Blackley Blue, CHIN, made by heating aniline salts with amidoazobenzene. Magenta.-See Fuchsin above.

Malachite Green, Benzaldehyde Green, or Victoria Green, 3CH ̧N2C1.2ZnCl2+H2O, made by the condensation of benzaldehyde with dimethylaniline, and the subsequent addition of hydrochloric acid and zinc chloride.

Martius's Yellow, C1H,N,O,SNa, made by the action of nitric acid on a-naphthol-monosulphonic acid.

Mauvein (hydrochloride), or Aniline Violet, CHAN,Cl, made by the action of chromic acid on aniline containing some toluidine.

Methyl Orange, C1H12N,SO,Na, made by the successive action of nitrous acid and methylaniline upon para-amidobenzene-sulphonic acid; it is the sodium salt of helianthin.

Methyl Violet, C2HN,Cl, made by oxidizing dimethyl-aniline with metallic salts.

18

Methylene Blue, C1H1N,SCI, made by heating amido-dimethylaniline with sulphide of iron. Naphthol Yellow, CH,N2O,SK, made by the action of nitric acid on a-naphthol-trisulphonic acid.

Nigrosin, CsH1N3, made by heating aniline salts with nitrobenzene.

Night Blue, CHNO (the hydrochloride of this is the commercial dye), made by heating pararosaniline with aniline and benzoic acid. Pararosaniline (chloride), C1H1N,Cl, made by oxidizing a mixture of para-toluidine and aniline with arsenic acid, or nitrobenzene.

18

Phenylene Brown. See Aniline Brown above. Ponceaux, or Bordeaux.-Various derivatives of azonaphthalene. "Ponceau 3R," C19H16N2O, S,Na, is made by combining diazo-cumene chloride with B-naphthol-disulphonic acid.

Primulin, CH,,NS(?), made by the action of sulphuric acid on thiotoluidine.

Resorcin Yellow, or Tropæolin, O, CHINOS, made by the action of diazobenzene-sulphonic

acid on resorcin.

Rhodamine (hydrochloride), CHNO,C1, made by the action of phosphorus trichloride on fluoresceïn, and treatment of the product with diethylamine.

Roccellin, CH1N,O,SNa, made by the action of B-naphthol on the diazo-compound of naphthionic acid.

Rosaniline.-See Fuchsin above. Rose Bengale, CH,Cl2I,O,K2, made by the successive action of chlorine and iodine upon fluorescein.

Rosolic Acid, CH18O3, closely allied to aurin; neither aurin nor rosolic acid is specially valuable.

Safranin, CaHN.Cl, made by the oxidation of a mixture of toluylene-diamine and aniline or toluidine.

Tropaolin. This name is applied to various compounds made by the successive action of nitrous acid and phenols upon amidobenzene sulphonic acids. See Resorcin Yellow above.

Úranin, CH,O,Na2, the sodium salt of fluorescein (which see above).

Victoria Green.-See Malachite Green above. Victoria Orange.-See Aniline Orange above. BIBLIOGRAPHY. Schultz, Die Chemie des Steinkohlentheers (Brunswick, 1890); Villon, Traité pratique des matières colorantes artificielles (Paris, 1890); Cazeneuve, Répertoire analytique des matières colorantes artificielles (Lyons, 1893); Schultz and Julius, Systematic Survey of the Organic Coloring Matters, translated by Green (New York, 1894); Hurst, Dic

tionary of the Coal-Tar Colors (London, 1896); Lefèvre, Traité des matières colorantes organiques artificielles (2 vols., Paris, 1896); Seyewetz and Sisley, Chimie des matières colorantes artificielles (Paris, 1897); Benedikt, Chemistry of the Coal-Tar Colors, translated by Knecht (London, 1900); Nietzki, Chemistry of the Organic Dyestuffs, translated by Collin and Richardson (London, 1892; newer German edition, Berlin, 1901). A journal devoted to the progress of the coal-tar industry has, since 1877, been published in Berlin by Friedländer, under the title, Fortschritte der TheerfarbenIndustrie und verwandter Industriezweige. The most important dyestuffs will be found described in some detail under their special names. See also DYEING; TEXTILE PRINTING.

COAL VILLE. A town of Leicestershire, England, 16 miles northwest of Leicester, in the midst of a coal district. Population, in 1901, 15,300.

COALVILLE. A city and the county-seat of Summit County, Utah, 40 miles southeast of Utah, B 1). It is in a coal-mining region. PopOgden; on the Union Pacific Railroad (Map: ulation, in 1890, 1166; 1900, 808.

COAN, kỡăn, Tirus (1801-82). An Ameri can missionary, born in Connecticut. He was ordained as a Congregational minister in 1833, and in that year made a trip of exploration to Patagonia, where he wished to establish a mission. Circumstances were unfavorable, and he returned, but soon afterwards went to the Hawaiian Islands, and for forty-seven years was stationed as a missionary at Hilo. Besides his work as a missionary, Dr. Coan published many two books entitled Adventures in Patagonia valuable papers on the volcanoes of Hawaii, and (1880) and Life in Hawaii (1881).

COANZA, kô-änʼzå. See KUANZA.

COASTAL PLAIN. In physiography, the name given to a portion of the North American Continent bordering the Atlantic Ocean and the Gulf of Mexico. From New York to Georgia the Coastal Plain includes the strip of low-lying lands that is limited on the east by the Atlantic and on the west by the first foot-hills of the Appalachian Mountain system. In northern Alabama the Coastal Plain passes around the southern limit of the Appalachians, after which it widens out and reaches northward as far as the Ohio River. West of the Mississippi River it extends with decreasing width southwestward into Mexico. The peculiar features of the Coastal Plain are its low elevation and the predominance of stratified rock-formations of recent geological age. On the outer border the surface is flat and raised but little above sea-level; toward the interior there is an increasing diversity of relief owing to the higher elevation and the extensive erosion by streams. The western limit of the plain, where the horizontal strata give way to the upturned and eroded rocks of the Appalachians, is marked by a sharp slope and by numerous cataracts. Geologically the Coastal Plain consists of Cretaceous, Tertiary, and Quaternary beds, which still retain the relative positions they acquired during deposition, although they have since been elevated above sea-level. Consult Mill, The International Geography (New York, 1900). See AMERICA; UNITED STATES.