See also:

• INDIGO (earlier indico, from Lat. indicum, the Indian sub-stance or dye; the Sans. name was niti, from nila, dark blue, and this through Arab. al-nil, annil, gives " aniline ")

INDIGO (earlier indico, from See also:

• LAT

Lat. indicum, the See also:

• INDIAN

Indian sub-stance or dye; the Sans. name was niti, from nila, dark See also:

• BLUE (common in different forms to most European languages)

blue, and this through Arab. al-nil, annil, gives " See also:

• ANILINE, PHENYLADIINE, or AMINOBENZENE, (C6H5NH2)

aniline ")  one of the most important and valuable of all dyestuffs . Until comparatively recently it was obtained exclusively from the aqueous See also:

• EXTRACT (from Lat. extrahere, to draw out)

extract of certain See also:

• PLANTS

plants, principally of the genus Indigofera which belongs to the natural See also:

• ORDER
• ORDER (through Fr. ordre, for earlier ordene, from Lat. ordo, ordinis, rank, service, arrangement; the ultimate source is generally taken to be the root seen in Lat. oriri, rise, arise, begin; cf. " origin ")
• ORDER, HOLY

order See also:

• LEGUMINOSAE

Leguminosae . Small quantities are also obtained from Lonchocar pus eyanescens (See also:

• WEST
• WEST, BENJAMIN (1738-1820)
• WEST, NICHOLAS (1461-1533)

west See also:

• COAST (from Lat. costa, a rib, side)

coast of See also:

• AFRICA
• AFRICA, ROMAN

Africa), Polygonum lintorium (See also:

• CHINA

China) and the See also:

• WOAD

woad plant Isatis tinctoria . The latter is of See also:

• HISTORICAL

historical See also:

• INTEREST

interest, since up to the See also:

• MIDDLE

middle of the 17th See also:

• CENTURY (from Lat. centuria, a division of a hundred men)

century it was the only See also:

• BLUE (common in different forms to most European languages)

blue dyestuff used by dyers in See also:

• ENGLAND
• ENGLAND, THE CHURCH OF

England and on the adjoining See also:

• CONTINENT (from Lat. continere, "to hold together "; hence " connected," " continuous ")

continent; at the See also:

• PRESENT

present See also:

• TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
• TIME, MEASUREMENT OF
• TIME, STANDARD

time woad is still cultivated in See also:

• EUROPE

Europe, but serves merely as a ferment in the setting of the See also:

• FERMENTATION

fermentation See also:

• INDIGO (earlier indico, from Lat. indicum, the Indian sub-stance or dye; the Sans. name was niti, from nila, dark blue, and this through Arab. al-nil, annil, gives " aniline ")

indigo vat or so-called " woad vat " used in See also:

• WOOL, WORSTED AND WOOLLEN MANUFACTURES

wool See also:

• DYEING (0. Eng. dedgian, dealt ; Mid. Eng. deyen)

dyeing . The bulk of the natural indigo which is brought into the See also:

• MARKET (Lat. mercatus, trade or place of trade)

market comes from See also:

• INDIA
• INDIA, FRENCH

India, while smaller quantities are imported from See also:

• JAVA

Java, See also:

• GUATEMALA (sometimes incorrectly written GUATIMALA)
• GUATEMALA, or GUATEMALA LA NUEVA (i.e. " New Guatemala," sometimes written Nueva Guatemala, and formerly Santiago de los Caballeros de Guatemala)

Guatemala and other places . The plant from which indigo is made in See also:

• BENGAL
• BENGAL, BAY OF

Bengal is the Indigofera sumatrana, which is reared from See also:

• SEED (from the root seen in Lat. serere, to sow)

seed sown about the end of See also:

• APRIL

April or the beginning of See also:

• MARCH
• MARCH (1) (from Fr. marcher, to walk; the earliest sense in French appears to be " to trample," and the origin has usually been found in the Lat. marcus, hammer; Low Lat. marcare, to hammer; hence to beat the road with the regular tread of a soldier: cf.
• MARCH, AUZIAS (c. "1395-1458)
• MARCH, EARLS OF
• MARCH, FRANCIS ANDREW (1825– )

March . By the middle of See also:

• JUNE

June the plant has attained a height of from 3 to 5 ft., and it is at this See also:

• PERIOD
• PERIOD (Gr. irepioSos, a going or way round, circuit, aepi, round, and &Sis, way, road)

period that the first manufacturing begins, a second See also:

• CROP (a word common. in various forms, such as Germ. Kropf, to many Teutonic languages for a swelling, excrescence, round head or top of anything; it appears also in Romanic languages derived from Teutonic, in Fr. as troupe, whence the English " crupper "

crop being obtained in See also:

• AUGUST (originally Sextilis)

August . The indigo is contained in the See also:

• LEAF (O. Eng. leaf, cf. Dutch loof, Ger. Laub, Swed. lof, &c.; possibly to be referred to the root seen in Gr. Ma-eta, to peel, strip)

leaf of the plant in the See also:

• FORM (Lat. forma)

form of a colourless See also:

• GLUCOSIDE

glucoside, known as indican, C14H1706N•3H20 . This substance is soluble in See also:

• WATER

water and by the See also:

• JOINT (through Fr. from Lat. junctum, jungere, to join)

joint See also:

• ACTION

action of an See also:

• ENZYME (Gr. Eve uµos, leavened, from v, in, and Om, leaven)

enzyme, contained in the leaf, and atmospheric See also:

• OXYGEN (symbol 0, atomic weight 16)

oxygen it yields indigotine, the colouring See also:

• MATTER

matter of indigo . It is on these facts that the manufacturing of indigo from the plant is based . The plant is cut See also:

• EARLY
• EARLY, JUBAL ANDERSON (1816-1894)

early in the See also:

• MORNING

morning and transported to the factory in See also:

• BULLOCK, WILLIAM (c. 1657-c. 1740)

bullock carts . Here it is steeped in water in steeping vats having a capacity of about r000 cub. ft. for periods varying, according to circumstances, from nine to fourteen See also:

• HOURS, CANONICAL

hours, when the liquid—the See also:

• COLOUR (Lat. color, connected with celare, to hide, the root meaning, therefore, being that of a covering)

colour of which varies from a See also:

• BRIGHT, JOHN (1811-188g)
• BRIGHT, SIR CHARLES TILSTON

bright See also:

• ORANGE
• ORANGE (Citrus Aurantium)
• ORANGE, HOUSE OF

orange to an See also:

• OLIVE (Olea europaea)

olive See also:

• GREEN, A
• GREEN, ALEXANDER HENRY (1832—1896)
• GREEN, DUFF (1791—1875)
• GREEN, JOHN RICHARD (1837—1883)
• GREEN, MATTHEW (1696-1737)
• GREEN, THOMAS HILL (1836-1882)
• GREEN, VALENTINE (1739–1813)
• GREEN, WILLIAM HENRY (.1825–1900)

green—is run into the beating vats which See also:

• LIE, JONAS LAURITZ EDEMIL (1833—1908)
• LIE, MARIUS SOPHUS (1842–1899)

lie at a See also:

• LOWER

lower level .

The beating, the See also:

• OBJECT

object of which is to bring the liquor as freely as possible into contact with the See also:

• AIR (from an Indo-European root meaning " breathe," " blow ")
• AIR, or ASBEN

air, was formerly done by striking the See also:

• SURFACE

surface with See also:

• BAMBOO

bamboo sticks, but is now effected either by means of a See also:

• PADDLE

paddle See also:

• WHEEL (0. Eng. hweol, hweohl, &c., cognate with Icel. hjol, Dan. hiul, the Indo-European root is seen in Sanskrit chakra, Gr. r in Aos, circle, whence " cycle ")
• WHEEL, BREAKING ON THE

wheel or by forcing a current of air from a See also:

• STEAM
• STEAM (0. Eng. steam, vapour, smoke, cf. Du. steam; the origin is unknown)

steam blower or a See also:

• COMPRESSOR

compressor through the liquid . When the beating is finished, the precipitated indigo is allowed to See also:

• SETTLE
• SETTLE, ELKANAH (1648–1724)

settle, the supernatant liquid being See also:

• DRAWN

drawn off and run to See also:

• WASTE (O. Fr. wast, guast, gast, gaste; Lat. vastus, vast, desolate)

waste . The indigo mud thus obtained, which is known as mal, is strained, boiled for a See also:

• SHORT, FRANCIS JOB (1857– )

short period for the purpose of sterilizing, formed into bars, cut into blocks of about 3 in. See also:

• CUBE (Gr. K46os, a cube)

cube and dried.' The actual amount of colouring matter yielded by the leaf is but small, averaging, according to Ch . Rawson, 0.5% , but the yield from the whole plant is considerably less, since the stalks and twigs contain practically no colour . Since the introduction on a large See also:

• SCALE
• SCALE (1) A

scale of synthetic indigo efforts have been made in India and in Java to See also:

• PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place the cultivation of the plant and the manufacture of the natural product on a more scientific basis . But although many important improvements have been achieved from the agricultural as well as from the manufacturing point of view, resulting no doubt in the retension of a portion of the See also:

• INDUSTRY (Lat. industria, from indu-, a form of the pre, position in, and either stare, to stand, or struere, to pile up)

industry, the synthetic product has gained the upper See also:

• HAND
• HAND (a word common to Teutonic languages; cf. Ger. Hand, Goth. handus)
• HAND, FERDINAND GOTTHELF (1786-185r)

hand and is likely to retain it . Natural indigoes vary considerably in See also:

• COMPOSITION
• COMPOSITION (Lat. compositio, from componere, to put together)

composition, containing in some qualities as much as 90% and in others as little as 20% of colouring matter . The blue colouring matter which indigo contains is known as indigotine, but there are usually also present in small quantities other colouring matters such as indigo red or indirubrine, a yellow colour known as kaempferol, indigo green and indigo See also:

• BROWN
• BROWN, CHARLES BROCKDEN (1771-181o)
• BROWN, FORD MADOX (1821-1893)
• BROWN, FRANCIS (1849- )
• BROWN, GEORGE (1818-188o)
• BROWN, HENRY KIRKE (1814-1886)
• BROWN, JACOB (1775–1828)
• BROWN, JOHN (1715–1766)
• BROWN, JOHN (1722-1787)
• BROWN, JOHN (1735–1788)
• BROWN, JOHN (1784–1858)
• BROWN, JOHN (1800-1859)
• BROWN, JOHN (1810—1882)
• BROWN, JOHN GEORGE (1831— )
• BROWN, ROBERT (1773-1858)
• BROWN, SAMUEL MORISON (1817—1856)
• BROWN, SIR GEORGE (1790-1865)
• BROWN, SIR JOHN (1816-1896)
• BROWN, SIR WILLIAM, BART
• BROWN, THOMAS (1663-1704)
• BROWN, THOMAS (1778-1820)
• BROWN, THOMAS EDWARD (1830-1897)
• BROWN, WILLIAM LAURENCE (1755–1830)

brown, as well as indigo See also:

• GLUTEN

gluten and more or less See also:

• MINERAL

mineral matter . The bulk of the indigo which now comes into the See also:

• EUROPEAN

European market is prepared synthetically from See also:

• COAL

coal See also:

• TAR

tar . The following figures indicate the values of the imports into England of natural and synthetic indigo, and are taken from the See also:

• OFFICIAL (Late Lat. QJicialis, for class. Lat. apparitor, from officium, office, duty)

official See also:

• BOARD (O. Eng. bord)

Board of See also:

• TRADE (O. Eng. trod, footstep, from tredan, to tread; in M. Eng. the forms teed, trod and trade appear, the last in the sense of a beaten track)
• TRADE, BOARD OF

Trade returns: Natural Indigo . Synthetic Indigo . 1899 £986,090 ..

1900 542,089 .. 1901 788,82o 1902 498,043 £143,613 1903 262,775 110,970 1904 316,070 83,397 1905 116,902 121,269 .1906 111,455 147,325 1907 151,297 158,481 1908 136,882 134,052 During the period 1899-1908, the See also:

• AVERAGE

average See also:

• PRICE
• PRICE, BARTHOLOMEW (1818–1898)
• PRICE, BONAMY (1807-1888)
• PRICE, RICHARD (1723-1791)

price of indigo had declined from a fraction under 3s. to about 2s . 22d. per lb . At first sight it might appear that the use of indigo in England was rapidly declining, but this does not necessarily follow when it is See also:

• BORNE, KARL LUDWIG (1786–1837)

borne in mind that See also:

• LONDON

London was formerly the distributing centre of natural indigo for the continent and See also:

• AMERICA

America . See also:

• CHEMISTRY
• CHEMISTRY (formerly "chymistry"; Gr. xvµela; for derivation see ALCHEMY)

Chemistry.—Our knowledge of the chemistry of indigo is largely derived from the classical researches of A. von See also:

• BAEYER, JOHANN FRIEDRICH WILHELM ADOLF VON (1835– )

Baeyer and his collaborators . In 1841 See also:

• ERDMANN
• ERDMANN, JOHANN EDUARD (1805-1892)

Erdmann and See also:

• LAURENT, FRANCOIS (1810–1887)

Laurent observed that on oxidation indigo yielded See also:

• ISATIN, C8H5NO2

isatin; and in 1848 Fritzsche obtained See also:

• ANILINE, PHENYLADIINE, or AMINOBENZENE, (C6H5NH2)

aniline by distilling the dyestuff with potash . In 187o A. v . Baeyer and Knop succeeded in preparing indigotine by See also:

• HEATING

heating isatin with See also:

• PHOSPHORUS (Gr. 4ws, light, sPEpety, to bear)

phosphorus trichloride, acetyl chloride and phosphorus . In the same See also:

• YEAR

year, C . Engler and A . Emmerling obtained small quantities of the dyestuff by heating nitroacetophenone with soda-See also:

• LIME
• LIME (O. Eng. lim, Lat. limes, mud, from linere, to smear)

lime and See also:

• ZINC

zinc dust, while in 1875 M. v . Nencki prepared it by the oxidation of indol by See also:

• OZONE

ozone .

Indol had been previously obtained from albuminoids by means of the See also:

• PANCREAS (Gr. rag, all; 1cpks, flesh)

pancreas ferment . It was not, however, until 1880 that v . Baeyer, who had been at See also:

• WORK

work on the subject since 1865, was able to obtain indigotine from more or less easily accessible coal tar derivatives of known constitution . The most important of these synthetic processes due to the researches of v . Baeyer was the See also:

• PRODUCTION (Lat. productionem, from producere, to pro-duce)

production of the dyestuff from ortho-nitrophenylpropiolic See also:

• ACID (from the Lat. root ac-, sharp; acere, to be sour)

acid _(see Pxoeiol.IC AcID), which yields indigotine on being treated with See also:

• CAUSTIC (Gr. rcavvraubs, burning)

caustic soda and a reducing See also:

• AGENT (from Lat. agere, to act)

agent such as See also:

• GRAPE

grape See also:

• SUGAR

sugar or xanthate of soda . Although used in small quantities in See also:

• CALICO

calico See also:

• PRINTING (from Lat. imprimere, O. Fr. empreindre)

printing, it never attained any commercial importance as a means of producing indigo, the cost of production being far too high . Many synthetic processes of preparing indigotine have since been devised, but the one which stands out pre-eminently from a technical point of view and the one which ultimately led to the commercial success of the synthetic product is that of Heumann who showed in 1890 that indigotine can be prepared by melting phenylglycocoll ' For a full See also:

• ACCOUNT
• ACCOUNT (through O. Fr. acont, Late Lat. comptum, cornputare, to calculate)

account of the manufacture of indigo in See also:

• NORTHERN

northern See also:

• BEHAR, or BIHAR

Behar see Ch . Rawson, Journ . See also:

• SOC

Soc . Dyers and Colourists (See also:

• JULY

July 1899) . (phenylglycine), See also:

• C6H6

C6H6•NH•See also:

• CH2
• CH2(OH)

CH2•000H, with caustic alkalis . The yield was at first very unsatisfactory .

It was subsequently found, however, that by starting with phenylglycocoll-ortho-carboxylic acid, the yield was sufficiently See also:

• GOOD, JOHN MASON (1764-1827)

good to render the See also:

• PROCESS

process a See also:

• PRACTICAL

practical success . The starting-point for the manufacture of synthetic indigo is See also:

• NAPHTHALENE, C

naphthalene, C,oH8, which is oxidized, by heating with concentrated sulphuric acid in the presence of a little See also:

• MERCURY
• MERCURY (MERCU1uus)
• MERCURY (symbol Hg, atomic weight = 2oo)

mercury, to See also:

• PHTHALIC

phthalic anhydride, C,See also:

• H4(Sr, Ba, Ca)Al2(SiOa)6+31420. H 4CaAl2(SiO3)

H4(CO)2O, which is then converted into ortho-aminobenzoic acid, See also:

• C6H4
• C6H4(CH213r)2

C6H4(See also:

• NH2

NH2)(See also:

• CO2H

CO2H), by treatment with an alkaline hypochlorite . This acid is then condensed with monochloracetic acid to form phenylglycocoll-ortho-carboxylic acid, C6H4(NH•CH,•CO2H)(CO2H), which on being melted with caustic See also:

• ALKALI

alkali yields indoxylic acid, C6H4<CNH) ~C•CO2H,and this readily losescarbondioxide andpasses over into indoxyl,See also:

• C5H4

C5H4< NH)>CH . By alkaline oxidation indoxyl is converted into indigotine . The patent literature of processes for bringing about the See also:

• CONVERSION (Lat. conversio, from convertere, to turn or ,change)

conversion of the phenylglycine or its carboxylic acid into indoxylic acid, indoxyl and indigotine is enormous; a circumstance due to the fact that the efficiency of this operation controls the price of the synthetic dyestuff . Caustic soda has been practically given up, being replaced partly or wholly by caustic potash ; in addition, alkaline earths, sodamide, nitrides, alkali carbides, &c., have been used . In 1906, Meister, See also:

• LUCIUS

Lucius and Bruning patented the addition of See also:

• LEAD
• LEAD (pronounced iced)

lead and See also:

• SODIUM [symbol Na, from Lat. natrium; atomic weight 23.00 (0=16)]

sodium to a mixture of caustic potash and soda; the Basler Chemische Fabrik use a mixture of caustic potash and soda at 210°-260°; See also:

• LEON
• LEON, LUIS PONCE DE (1527-1591)
• LEON, MOSES BEN SI
• LEON, or LEON DE LAS ALDAMAS

Leon Lilienfeld added slaked lime or See also:

• MAGNESIA

magnesia to the fused alkali, with a subsequent heating in a current of See also:

• AMMONIA (NH3)

ammonia at 15o°-30o° and in 1908 patented a process wherein the melt is heated under greatly reduced pressure; this gave a yield of 8o-9o% . Synthetic indigo comes into the market chiefly in the form of a 20 °/o See also:

• PASTE (O. Fr. paste, modern pate, Late Lat. pasta, whence also in Span., Port. and Ital., from Gr. 1r&vrrl or 1raara, barley porridge, or salted pottage, ir&ao'ety, to sprinkle with salt)

paste but is also sold in the solid See also:

• STATE
• STATE, GREAT OFFICERS OF

state in the form of a See also:

• POWDER (through O. Fr. puldre, modern poudre, from Lat. pulvis, pulveris, dust)

powder . Indigotine, C16H,oN202, is a derivative of indol and its constitution is I CO:C/CO i \ \./\NHS \NH/\/ It can be prepared in as almost pure state by extracting good qualities of Bengal or Java indigo or synthetic indigo with boiling See also:

• NITROBENZENE, C6H6NO2

nitrobenzene, from which it crystallizes on cooling in dark blue crystals having a metallic sheen . When heated in an open See also:

• VESSEL (O. Fr. vaissel, from a rare Lat. vascellum, dim. of vas, vase, urn)

vessel it readily volatilizes, yielding a See also:

• VIOLET

violet vapour which condenses on cooling in the form of crystals . Indigotine is also soluble in boiling aniline oil, See also:

• QUINOLINE (Benzopyridine), C9H7N

quinoline, glacial acetic acid and See also:

• CHLOROFORM (trichlor-methane), CHC13

chloroform, but is insoluble in water, dilute acids and alkalis and See also:

• ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

ordinary solvents like See also:

• ALCOHOL

alcohol, See also:

• ETHER, (C2H5)2O

ether, &c . By nitric acid and many other oxidizing agents it is readily converted into isatin, C3H6NO2 .

Heated with concentrated sulphuric acid it yields a disulphonic acid, C16H8N,02(SO,H)2, the sodium See also:

• SALT (a common Teutonic word, cf. Dutch zout, Ger. Salz, Scand. salt; cognate with Gr. &Xs, Lat. sal)
• SALT, SIR TITUS, BART

salt of which finds application as an acid colour in wool dyeing under the name of Indigo See also:

• CARMINE

carmine) . By the action of reducing agents, indigotine is converted into indigo See also:

• WHITE
• WHITE, ANDREW DICKSON (1832– )
• WHITE, GILBERT (1720–1793)
• WHITE, HENRY KIRKE (1785-1806)
• WHITE, HUGH LAWSON (1773-1840)
• WHITE, JOSEPH BLANCO (1775-1841)
• WHITE, RICHARD GRANT (1822-1885)
• WHITE, ROBERT (1645-1704)
• WHITE, SIR GEORGE STUART (1835– )
• WHITE, SIR THOMAS (1492-1567)
• WHITE, SIR WILLIAM ARTHUR (1824--1891)
• WHITE, SIR WILLIAM HENRY (1845– )
• WHITE, THOMAS (1628-1698)
• WHITE, THOMAS (c. 1550-1624)

white, CI6H12N2O2, which is readily soluble in alkalis or See also:

• MILK (0. Eng. meoluc; from a common Indo-European root, cf. Lat. mulgere, Gr. ?t dXyetv)

milk of lime with a yellow colour . On exposing the alkaline See also:

• SOLUTION (from Lat. solvere, to loosen, dissolve)

solution to the air the indigo white is rapidly oxidized back to indigotine, and on these two reactions the application of indigo in dyeing and printing is based . (See DYEING and TEXTILE PRINTING.) Various halogen (See also:

• CHLORINE (symbol Cl, atomic weight 35`46 (0=16)

chlorine and See also:

• BROMINE (symbol Br, atomic weight 79-96)

bromine) substitutive derivatives of indigotine have been introduced which, while not differing essentially from ordinary indigo in their properties, produce for the most See also:

• PART

part redder shades in dyeing . They are claimed to be faster and brighter See also:

• COLOURS, MILITARY

colours . It has been shown by Friedlander (Ber., 1909, 42, p . 765) that the reddish violet colouring matter obtained from the colour-yielding glands of the mollusc Murex brandaris, by means of which the famous Tyrian See also:

• PURPLE

purple of the ancients was dyed, is a dibromindigo, C16H8Br2N202 . A new departure in the synthetic dyestuffs belonging to the indigo See also:

• GROUP

group was inaugurated by the See also:

• DISCOVERY

discovery in 1906 by P . Friedlander of thioindigo red, a derivative of thionaphthen, which is formed from phenylthioglycol-ortho-carboxylic acid, CeH.<C01 COzH . This substance, on boiling with alkali and then with dilute acid yields thioindoxyl, C6H4< SO>CH2, which is converted by alkaline oxidation into thioindigotin, having the conotitution C6Hs< SO>C:C< CO >C6H4 . The new dye-stuff is therefore analogous to indigotine, from which it differs by having the imino See also:

• GROUPS
• GROUPS, THEORY

groups replaced by See also:

• SULPHUR

sulphur atoms . Thioindigo red can be readily crystallized from boiling See also:

• BENZENE, C6H6

benzene, and forms reddish brown crystals possessing a metallic reflex .

Thioindigo See also:

• SCARLET

scarlet, C6H4< SO>C=C< H4>NH, is also obtained synthetically . Both products come into the market in the form of pastes and are used in dyeing like indigo (see DYEING) . (E . K.) • Although bright shades of blue are produced with this derivative, they are not fast .