needles, obtained by treating the brown precipitate from madder decoction with perchloride or pernitrate of iron, and adding H Cl or SO, Rubiacic acid C31 H, O17 lemon-yellow powder, the result of the oxidation of rubiacin. Rubian is the yellow bitter principle of madder, and is obtained from the brown precipitate of madder, by washing with cold water; Pectic acid dissolves along with it. Xanthin, a brownish syrup, obtained by evaporating the decoction of madder. — Alizarin appears to be the only colouring matter in madder, according to Schunck, by whom the above facts were ascertained. There are also 2 resins in madder,

Garencin, an impure body, is obtained by SO, from madder. Archil (orseille). A red colouring matter from the roccella tinctoria, produced by the action of urine or carbonate of ammonia. Archil contains two colouring substances, alpha orcein (C18 H10 NO), and beta orcein produced from the first by oxidation, and erythroleic acid and azoerythrein. Orcin'(C8H12 Og) in colourless 4-sided prisms, is prepared from the fresh lichen by boiling with alcohol, filtering, distilling off the spirit, exhausting the extract by water, and crystallizing. When exposed to air and NH, it is changed into orcein, or beta orcein, a fine red body. - Lecanorin (C18 H. Og), silky colourless needles, extracted by means of ether, and changing by the action of alkalies and air into orcin and carbonic acid. Erythric acid, Erythrin (C34 H19 O15) snow-white scales, obtained by water and alcohol from roccella tinctoria. Erythrylin (C22 H16 O6), (white powder insoluble in water. Erythrin, by boiling with water, is converted into Picroerythrin (C34H24O20) crystals, which may be separated by evaporation and solution in alcohol. Alpha orsellic acid (C32H15O13), white needles, obtained by treating archil lichen, from South America, with milk of lime, precipitating by HCl, and crystallizing the precipitate in alcohol. Beta orsellic acid (C34H17014), obtained by a similar process from the Cape of Good Hope archil. Alpha orsellesic acid (C16H,O,), crystals procured by neutralizing freshly precipitated orsellic acid with barytes water, precipitating by HCl, and crystallizing from alcohol. Roccelline (C38H170,5), silky needles by the action of alcohol on crude orsellic acid. Pseudo-orcine (C10H13010), large colourless crystals from the lime solution of Roccella Montagnei, by passing CO2 through it, and evaporating to a syrup. Ether dissolves orcine, and leaves pseudo-orcine, which may be crystallized from alcohol.

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(Stenhouse.) Various other substances are obtained from lichens, probably, like many of the preceding, products of oxidation, &c. Usnic acid, C38 H17 014, sulphur crystals from lichens. Cudbear (persio), a red matter from the lecanora tartarea by the action of gas ammoniacal liquor.

Draconin, dragon's blood. Red powder, without taste and smell. Specific gravity 1·19, insoluble in water; used as a tooth

powder and for varnishes, obtained from the Dracæna drago. Santalin. — Fine carmine powder, obtained by alcohol from the Pterocarpus Santalinus; tasteless, insoluble in water, soluble in alcohol, ether, and acetic acid. Brezilin, Fernambuc red, Brazil red. - Red powder, obtained from different species of cæsalpina, by digesting the rasped wood in water, evaporating the infusion to dryness, dissolving the residue in water, agitating with litharge to remove acid, evaporating; digesting the residue in alcohol, and evaporating. The residue is brezilin; it is soluble in alcohol, and water; alkalies render it violet. Sapan and Camwoods appear to contain the same colouring matter. Red ink is made by digesting 50 parts of Brazil wood in 200 of vinegar for 3 days, boiling for an hour, filtering, and to the liquid are added 6 parts each of gum arabic, sugar, and alum. Hæmatoxylin. Yellow 4-sided prisms, with a slight astringent taste; soluble in water, alcohol, and ether. It is often obtained in frosty weather crystallized in the preparation of logwood liquor for the printers. It is prepared by taking up an extract of logwood (Hæmatoxylon campeachianum) with water, evaporating, dissolving in ether; the ether is distilled off; the syrupy extract mixed with water, which gradually deposits crystals. H Cl colours it purple,. NO, reddens it, isinglass precipitates it. When dried at 212° it consists of C 63.6 H 4.50 31.8. Form, C40 H17 015. When its solution is mixed with NH, and allowed to stand in the air, and then acetic acid is added, a rust-coloured precipitate, hamatein, falls. Ammonia-hæmatein crystallizes out of a solution of hæmatoxylin in NH..

Carthamin, safflower. From the flowers of carthamus tinctorius, by digesting them in cold water, to which some acetic acid is added; a yellow colouring matter is thus taken up. The flowers are then digested in the solution of an alkaline carbonate, which takes up the red carthamin; the addition of acetic acid precipitates it; it is insoluble in water and dilute acids, slightly soluble in alcohol. Rouge is formed of carthamin pounded with talc, and is extensively used as a pigment for the face, &c. Cactin, a scarlet powder obtained from cactus speciosus, by a mixture of alcohol and ether.

Carmine, cochineal, red crystalline grains soluble in water and alcohol, insoluble in ether. Aqueous solutions become yellowish red by acids, by alkalies violet; precipitated by alum; it is obtained by dissolving out fat from cochineal by ether; dissolving and crystallizing out of alcohol.

BLUE COLOURS. Indigo is the product of the indigofera tinctoria; the plant is cut before flowering, and placed in a vat, covered with water and allowed to steep for 9 to 12 hours, where it ferments. The yellow steep liquor is drawn off by a plug at the bottom of the vat into another vessel, where it is beat and

stirred with bamboos for 1 to 3 hours, till the indigo granulates. When the grains are properly formed, cold water or lime water is added, and the liquor allowed to clear, and then drawn off. The indigo is placed in a copper boiler and gently boiled; it is then thrown on a filter, squeezed and dried.

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Blue Indigo. Blue rhombic needles, with a copper lustre, obtained by sublimation from common indigo by heating it between two platinum crucible covers; or it may be obtained as a powder from the indigo vat, by mixing, in a stoppered bottle, 5 indigo, 10 sulphate of iron, 15 slaked lime, and 60 water. After standing for some days the clear liquor is drawn off with a syphon; the indigo precipitates on the exposure of the liquor to the air; the indigo is to be washed with pure water and HCl, and lastly with alcohol. In this state it consists of C 73.28, H 3.82, N 10.69 O 12.21. Form. C16 H5 NO2. (Crum, Dumas.) White Indigo, Indigogene, C16 H, NO2+ H, is, according to the present view, blue indigo, with an additional atom of hydrogen. It exists in the indigo vat, and can be obtained by drawing off the vat liquor by means of a syphon filled with hydrogen, and mixing it with dilute HCl, to which sulphate of NH, has been added; a white precipitate falls of indigogene, which must be kept away from the air. It must be washed with boiling water, containing sulphate of NH,; it dissolves in alkalies; in dry air it retains its colour; soluble in alcohol, but insoluble in water and acids. Sulpho-indigotic acid, Saxon blue, Cerulin, Sulphindelic acid, C16 H1 NO 2SO3. When 1 part of blue indigo is left in contact with 8 parts of oil of vitriol for some days, at a common temperature, or at 130°, a blue solution is produced, while a purple substance remains -Sulphopurpuric acid, C32 H10 N2 04 2SO3The first acid is formed by the indigo losing an atom of water, while in the second acid the atom is doubled. Oxidation and Chlorization of Indigo. When indigo is dissolved in diluted NO, colourless needles of indigotic or anilic acid separate by concentration: they consist of C14 H4 NO,. When the preceding acid is acted on further by NO, yellow prisms of picric, or carbazotic acid, or bitter of Welter (C12H2 N3 O13) are formed. When purified indigo blue is treated with a mixture of equal parts of SO, and bichromate of potash previously dissolved in 25 parts of water, the mixture gently heated until there is a slight disengagement of CO2, and the liquid assumes a deep brown yellow colour; crystals make their appearance on cooling, which are reddish yellow rhombic prisms of Isatin: it is soluble in hot alcohol and water; the solution colours the skin. It consists of C16 H5 NO, or simply indigo with 2 atoms oxygen derived from the chromic acid. When isatin is heated with caustic potash, a compound of isatic acid (C16 H NO5) with potash is formed. When isatin is dissolved in sulphohydret of ammonia, a white powder

isatyde, C16 H6 NO, separates on cooling. When, through a saturated alcoholic solution of isatine, SH is passed, Sulphesatyde, C16 H. NO2 S2 grayish yellow crystals fall, mixed with sulphur. One atom of sulphur can be removed from this compound by treating a solution of it in alcohol by KO. On adding the latter, drop by drop, the liquid becomes red, and white crystals fall of sulphasatyde, C16 H6 NO3 S. When sulphasatyde is rubbed in a mortar with strong caustic potash, the colour changes to red, and deepens by the addition of alcohol. The powder, when washed with alcohol, water, and dissolved in potash, yields a black solution, which deposits black crystals of Indinate of potash. When these crystals are washed with alcohol, H Cl and water, they become Indine C16 H6 NO2. When sulphasatyde is treated with potash, yellow crystals of Hydrindine appear. Nitric acid converts Indine and Hydrindine into Nitrindine CT6 H, NO, O, NO2 — a violet powder. Sulphisatanous C16 H6 N 2SO2 02 NH10 2 Aq. is obtained by treating sulphesatyde with bisulphate of ammonia. Isatane, C16 H6 NO3, is a white powder

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obtained in the preceding process.

If a current of chlorine be passed through a solution of isatin, an atom of hydrogen is replaced by Cl, and a new compoundChlorisatin, (C16 NH4 04)—is produced; a substance crys

tallizing in orange yellow 4-sided prisms, dissolving in 50 parts of boiling water and alcohol; it is converted into chlorisatic acid by caustic potash (C16 H5 CI NO). By the further action of Cl, Bichlorisatin (C16 N H, O4) is produced in red prisms,

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16

3 Cl2

more soluble in alcohol and water than the preceding body. It forms an acid with potash. When chlorisatin is dissolved in hot sulphohydret of ammonia, Chlorisatyde, a yellowish white powder, separates on cooling (C16 H5 N CI 04). When chlorine is passed through an alcoholic solution of chlorisatin, pearly scales of chloranil (C12 Cl, O1) make their appearance, which are converted by potash into chloranilic acid. When chloranil is

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dissolved in hot NH, the solution becomes blood red, and crystals of ammonia chloranil (C12 H Cl1⁄2 N2 О) in the form of chesnut needles, appear. After the separation of this body, if HCl be added, chloranilam in needles separates. When chlorine is passed through water containing indigo blue in suspension, the whole becomes a yellow mass; when this is distilled, white needles, consisting of a mixture of chlorindatmin and chlorindoptic acid, condense in the neck of the retort, while chlorisatin and bichlorisatin remain in the retort. Bromine has a similar action to chlorine in all these cases of replacement.

Action of Alkalies on Indigo.

-When indigo blue is boiled with caustic potash (sp. grav. 1·45) it dissolves into a yellowish fluid,

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and, by evaporation, crystals of chrysanilic acid (C28 H11 N2 O6) and potash are obtained. When caustic potash (sp. grav. 1.35) is boiled with indigo blue, and finely powdered black oxide of manganese is added in small portions at a time, anthranilate (C14 H6 NO3) of potash is formed, which may be separated by crystallization. If indigo be decomposed by strong caustic potash or soda, and then distilled, aniline, a colourless oil, appears, (C12 H, N) with a sp. grav. 1·020, the boiling point at 360°, soluble in water and alcohol. It is obtained likewise among the oils of coal tar. When dry NH3 is passed through a solution of isatine in alcohol, dark yellow crystals of Imesatine (C16 H6 N O,) appear, in which oxygen is replaced by amidogen NH, or imidogen (NH) the rational formula being C16 H, N 2 Im. O2. Imasatine C16 H N Im. O, forms when caustic NH3, is brought in contact with an alcoholic solution of isatine. Amasatine, C16 H, N Ad. O,, a yellow body, obtained along with the preceding.

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2°

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Litmus, Lacmus, Turnsol.- Blue cubical cakes, which come to this country from Holland, are so termed. It is prepared by reducing the lichen Lecanora tartarea to powder, mixing it with urine, and leaving them for thirty days in contact, when the blue colour gradually appears. Litmus consists of four substances;

when it is boiled with water, and extracted with H Cl, a red matter remains, which is boiled with alcohol. This fluid takes up erythrolein and erythrolitmin, and some other bodies. Ether dissolves the two former, and drops the first as an oil on evaporating the ether (C26 H22 O4); while the erythrolitmin (C26 H23 018) is obtained as a red powder, by the total evaporation of the ether. When the alcoholic extract, unacted on by ether, is mixed with NH3, azolitmin is taken up. A red substance, termed spaniolitmin (C1 H, O16), is sometimes, though rarely, present in litmus. (Kane.)

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Litmus paper is prepared for testing by dipping letter paper into a filtered infusion of litmus, to which a small portion of carbonate of ammonia is added; or the paper may be previously dipped in a weak solution of that salt, and then into the litmus. YELLOW COLOURING MATTERS. - The most important yellow colours are quercitron, which is extensively used in dyeing, obtained from the bark of the quercus tinctoria, fustic or yellow wood (morus tinctoria), weld or woad (reseda luteola), anotto (bixa orellana), much employed to dye cheese and to colour tooth powder; turmeric, the root of the curcuma longa, principally used for testing ammonia, and to mix with curry powder; Persian berries (rhamnus cathartica); saffron, from the crocus sativus; parietin, from the parmelia parietina.