See also:

• IODINE (symbol I, atomic weight '26.92)

IODINE (See also:

• SYMBOL (Gr. o-uµ(3oXov, a sign)

symbol I, atomic See also:

• WEIGHT

weight '26.92)  , a chemical See also:

• ELEMENT (Lat. elementum)

element, belonging to the halogen See also:

• GROUP

group . Its name is derived from Gr. ioetb is (See also:

• VIOLET

violet-coloured), in allusion to the See also:

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

colour of its vapour . It was discovered in 1812 by B . See also:

• COURTOIS, JACQUES (1621–1676)

Courtois when investigating the products obtained from the See also:

• MOTHER

mother-liquors prepared by lixiviating See also:

• KELP (in M.E. culp or culpe, of unknown origin; the Fr. equivalent is varech)

kelp or burnt seaweed, and in 1815 L . J . See also:

• GAY, JOHN (1685-1732)
• GAY, MARIE FRANCOISE SOPHIE (1776-1852)
• GAY, WALTER (1856– )

Gay-Lussac showed that it was an element . See also:

• IODINE (symbol I, atomic weight '26.92)

Iodine does not occur in nature in the uncombined See also:

• CONDITION (Lat. condicio, from condicere, to agree upon, arrange; not connected with conditio, from condere, conditum, to put together)

condition, but is found very widely but sparingly distributed in the See also:

• FORM (Lat. forma)

form of iodides and iodates, chiefly of See also:

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

sodium and See also:

• POTASSIUM [symbol K (from kalium), atomic weight 39.114 0=16)]

potassium . It is also found in small quantities in See also:

• SEA (in O. Eng. sae, a common Teutonic word; cf. Ger. See, Dutch Zee, &c.; the ultimate source is uncertain)
• SEA, COMMAND OF THE

sea-See also:

• WATER

water, in some seaweeds, and in various See also:

• MINERAL

mineral and medicinal springs . Deep-sea weeds as a See also:

• RULE

rule contain more iodine than those which are found in the shallow See also:

• WATERS, TERRITORIAL

waters . Iodine is obtained either from kelp (the ashes of burnt sea-See also:

• WEED, THURLOW (1797—1882)

weed) or from the mother-liquors obtained in the See also:

• PURIFICATION

purification of See also:

• CHILE, or CHILI (derived, it is said, from the Quichua chin , cold, or tchili, snow)

Chile See also:

• SALTPETRE (from the Lat. sal, salt, Petra, a rock)

saltpetre . In the former See also:

• CASE
• CASE, JOHN (d. 1600)

case the seaweed is burnt in large heaps, care being taken that too high a temperature is not reached, for if the ash be allowed to fuse much iodine is lost by volatilization . The product obtained after burning is known either as kelp or varec .

Another method of obtaining kelp is to See also:

• HEAT (0. E. haktu, which like " hot," Old Eng. hat, is from the Teutonic type haita, hit, to be hot; cf. Ger. hitze, heiss; Dutch, hitte, heet, &c.)

heat the seaweed in large retorts, whereby tarry and ammoniacal liquors pass over and a very porous See also:

• RESIDUE (through the French, from the Lat. residuum, a remainder, from residere, to remain)

residue of kelp remains . A later method consists in boiling the weed with sodium carbonate; the liquid is filtered and hydrochloric See also:

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

acid added to the filtrate, when alginic acid is precipitated; this is also filtered off, the filtrate neutralized by See also:

• CAUSTIC (Gr. rcavvraubs, burning)

caustic soda, and the whole evaporated to dryness and carbonized, the residue obtained being known as kelp substitute . The kelp obtained by any of these methods is then lixiviated with water, which extracts the soluble salts, and the liquid is concentrated, when the less soluble salts, which are chiefly alkaline _chlorides, sulphates and See also:

• CARBONATES

carbonates, crystallize out and are removed . Sulphuric acid is now added to the liquid, and any alkaline sulphides and sulphites See also:

• PRESENT

present are decomposed, while iodides and bromides are converted into sulphates, and hydriodic and hydrobromicacids are liberated and remain dissolved in the See also:

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

solution . The liquid is run into the iodine still and gently warmed, See also:

• MANGANESE (symbol Mn; atomic weight, 54.93 (0=16)], a metallic chemical element. Its dioxide (pyrolusite)

manganese dioxide in small quantities being added from 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 to time, when the iodine distils over and is collected . In the second method it is found that the mother-liquors obtained from Chile saltpetre contain small quantities of sodium iodate NaIO3; this liquor is mixed with the calculated quantity of sodium bisulphite in large vats, and iodine is precipitated: 2NaI03+5NaHS03 =3NaHSO4+2Na2SO4+H20+12 . The precipitate is washed and then distilled from See also:

• IRON [symbol Fe, atomic weight 55.85 (0=16)]

iron retorts . Iodine may also be prepared by the decomposition of an iodide with See also:

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

chlorine, or by See also:

• HEATING

heating a mixture of an iodide and manganese dioxide with. concentrated sulphuric acid . Commercial iodine may be purified by mixing it with a little potassium iodide and then subliming the mixture; in this way any traces of See also:

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

bromine or chlorine are removed . J . S . See also:

• STAS, JEAN SERVAIS (1813–1891)

Stas recommends solution of thb iodine in potassium iodide and subsequent precipitation by the addition of a large excess of water, the precipitate being washed, distilled in See also:

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

steam, and dried in vacuo over solid See also:

• CALCIUM [symbol Ca, atomic weight 40.0 (o= x6)]

calcium nitrate, and then over solid caustic baryta .

Iodine is a greyish-See also:

• BLACK
• BLACK, ADAM (1784-1874)
• BLACK, JEREMIAH SULLIVAN (1810–1883)
• BLACK, WILLIAM (1841-1898)

black shining solid, possessing a metallic lustre and having somewhat the See also:

• APPEARANCE (from Lat. apparere, to appear)

appearance of See also:

• GRAPHITE

graphite . Its specific gravity is 4'948 (17°l4°) . It melts at 114.2° C. and boils at 184.35° C. under atmospheric pressure (W . See also:

• RAMSAY, ALLAN (1686-1758)
• RAMSAY, ALLAN (1713-1784)
• RAMSAY, ANDREW MICHAEL (1686-1743)
• RAMSAY, DAVID (1749—1815)
• RAMSAY, SIR WILLIAM (1852– )
• RAMSAY, SIR WILLIAM MITCHELL (185r– )

Ramsay and S . See also:

• YOUNG
• YOUNG, A
• YOUNG, ARTHUR (1741-1820)
• YOUNG, BRIGHAM (1801-1877)
• YOUNG, CHARLES MAYNE (1777–1856)
• YOUNG, EDWARD (1683–1765)
• YOUNG, JAMES (1811-1883)
• YOUNG, THOMAS (1773-1829)

Young) . The specific heat of solid iodine is 0.0541 (H . See also:

• KOPP, HERMANN FRANZ MORITZ (1817-1892)

Kopp) . Its latent heat of See also:

• FUSION

fusion is 11.7 calories, and its latent heat of See also:

• VAPORIZATION

vaporization is 23.95 calories (P . A . See also:

• FAVRE, JEAN ALPHONSE (1815-1890)
• FAVRE, JULES CLAUDE GABRIEL (1809-1880)

Favre and J . T . Silbermann) .

The specific heat of iodine vapour at See also:

• CONSTANT, BENJAMIN (1845-1902)

constant pressure is 0.03489, and at constant See also:

• VOLUME

volume x•02697 . It volatilizes slowly at See also:

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

ordinary temperatures, but rapidly on heating . Iodine vapour on heating passes from a violet colour to a deep 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 See also:

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

blue; this behaviour was investigated by V . See also:

• MEYER, CHRISTIAN ERICH HERMANN VON (18or-1869)
• MEYER, HEINRICH AUGUST WILHELM (1800-1873)
• MEYER, JULIUS LOTHAR (183o-1895)
• MEYER, KONRAD FERDINAND (1825-1898)
• MEYER, VICTOR (1848-1897)
• MEYER, [MARIE] PAUL HYACINTHE (184o- )

Meyer (Ber., r88o, 13, p . 394), who found that the See also:

• CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)

change of colour was accompanied by a change of vapour See also:

• DENSITY (Lat. densus, thick)

density . Thus, the density of See also:

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

air being taken as unity, See also:

• VICTOR
• VICTOR, GAIUS JULIUS (4th cent. A.D.)
• VICTOR, SEXTUS AURELIUS

Victor Meyer found the following values for the density of iodine vapour at different temperatures: T° C . 253 450 506 842 1027 1570 Density 8.89 8.84 8'73 6.08 5.75 5.67 This shows that the iodine See also:

• MOLECULE (from mod. Lat. molecula, the diminutive of moles, a mass)

molecule becomes less complex in structure at higher temperatures . Iodine possesses a characteristic penetrating See also:

• SMELL (connected etymologically with " smoulder " and " smoke ")

smell, not so pungent, however, as that of chlorine or bromine . It is only very sparingly soluble in water, but dissolves readily in solutions of the alkaline iodides and in See also:

• ALCOHOL

alcohol, See also:

• ETHER, (C2H5)2O

ether, See also:

• CARBON (symbol C, atomic weight 12)

carbon bisulphide, See also:

• CHLOROFORM (trichlor-methane), CHC13

chloroform, and many liquid See also:

• HYDROCARBONS

hydrocarbons . Its solutions in the alkaline iodides and in alcohol and ether are 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 in colour, whilst in chloroform and carbon bisulphide the solution is violet . It appears to combine with the solvent (P . Waentig, Zeit. phys .

Chem., 1909, p . 513) . Its chemical properties closely resemble those of chlorine and bromine; its See also:

• AFFINITY (Lat. affinitas, relationship by marriage, from offinis, bordering on, related to; finis, border, boundary)
• AFFINITY, CHEMICAL

affinity for other elements, however, is as a rule less than that of either . It will only combine with See also:

• HYDROGEN [symbol H, atomic weight x-oo8 (0=16)]

hydrogen in the presence of a catalyst, but combines with many other elements directly; for example, See also:

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

phosphorus melts and then inflames, See also:

• ANTIMONY (symbol Sb, atomic weight 120.2)

antimony See also:

• BURNS, JOHN (1858– )
• BURNS, ROBERT (1759-1796)
• BURNS, SIR GEORGE

burns in the vapour, and See also:

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

mercury when heated with iodine combines with it rapidly . It is completely oxidized to iodic acid when boiled with fuming nitric acid . It is soluble in a solution of caustic potash, a dilute solution most probably containing the hypoiodite, which, however, changes slowly into iodate, the change taking See also:

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

place rapidly on warming . When See also:

• ALKALI

alkali is added to aqueous iodine, followed immediately by either soda water or sodium bicarbonate, most' of the See also:

• ORIGINAL

original iodine is precipitated (R . L . See also:

• TAYLOR
• TAYLOR, ANN (1782-1866)
• TAYLOR, BAYARD (1825–1878)
• TAYLOR, BROOK (1685–1731)
• TAYLOR, ISAAC (1787-1865)
• TAYLOR, ISAAC (1829-1901)
• TAYLOR, JEREMY (1613-1667)
• TAYLOR, JOHN (158o-1653)
• TAYLOR, JOHN (1704-1766)
• TAYLOR, JOSEPH (c. 1586-c. 1653)
• TAYLOR, MICHAEL ANGELO (1757–1834)
• TAYLOR, NATHANIEL WILLIAM (1786-1858)
• TAYLOR, PHILIP MEADOWS (1808–1876)
• TAYLOR, ROWLAND (d. 1555)
• TAYLOR, SIR HENRY (1800-1886)
• TAYLOR, THOMAS (1758-1835)
• TAYLOR, TOM (1817-1880)
• TAYLOR, WILLIAM (1765-1836)
• TAYLOR, ZACHARY (1784-1850)

Taylor, Jour . Chem . See also:

• SOC

Soc., 1897, 71, p . 725, and K .

J . P . See also:

• ORTON, JOB (1717–1783)

Orton, ibid. p . 830) . Iodine can be readily detected by the characteristic blue coloration that it immediately gives with See also:

• STARCH

starch 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; the colour is destroyed on heating, but returns on cooling provided the heatirig has not been too prolonged . Iodine in the presence of water frequently acts as an oxidizing See also:

• AGENT (from Lat. agere, to act)

agent; thus arsenious acid and the arsenites, on the addition of iodine solution, are converted into See also:

• ARSENIC (symbol As, atomic weight 75.0)

arsenic acid and arsenates . A dilute solution of iodine prevents the decomposition of hydrogen peroxide by colloidal See also:

• PLATINUM [symbol Pt, atomic weight 145.0 (0=16)]

platinum (G . Bredig, Zeit. phys . Chem., 1899, p . 258; 1901, 37, p . 323 . Iodine finds application in organic See also:

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

chemistry, forming addition products with unsaturated compounds, the See also:

• COMBINATION (Lat. combinare, to combine)

combination, how-ever, being more slow than in the case of chlorine or bromine .

It rarely substitutes directly, because the hydriodic acid produced reverses the reaction; this can be avoided by the presence of precipitated mercuric See also:

• OXIDE

oxide or iodic acid, which react with the hydriodic acid as fast as it is formed, and consequently remove it from the reacting See also:

• SYSTEM

system . As a rule it is preferable to use iodine in the presence of a See also:

• CARRIER
• CARRIER, JEAN BAPTISTE (1956-1794)

carrier, such as amorphous phosphorus or ferrous'iodide or to use it with a solvent . It is found that most organic compounds containing the grouping See also:

• CH3

CH3•CO•C— or CH3.CH(OH).C— in the presence of iodine and alkali give See also:

• IODOFORM, CHI3

iodoform CHI3 . Hydriodic acid, HI, is formed by the See also:

• DIRECT

direct See also:

• UNION
• UNION (known locally as Union Hill and officially as Town of Union)

union of its components in the presence of a catalytic agent; for this purpose platinum black is used, and the hydrogen and iodine vapour are passed over the heated substance . On shaking up iodine With a solution of sulphuretted hydrogen irl water, a solution of hydriodic acid is obtained, See also:

• SULPHUR

sulphur being at the same time precipitated . The acid cannot be prepared by the See also:

• ACTION

action of concentrated sulphuric acid on an iodide on See also:

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

account ofsecondary reactions taking place, which result in the formation of See also:

• FREE

free iodine and sulphur dioxide . The usual method is to make a mixture of amorphous phosphorus and a large excess of iodine and then to allow water to drop slowly upon it; the reaction starts readily, and the See also:

• GAS

gas obtained can be freed from any admixed iodine vapour by passing it through a See also:

• TUBE (Lat. tuba)

tube containing some amorphous phosphorus . It is a colourless See also:

• SHARP, GRANVILLE (1735-1813)
• SHARP, JAMES (1618-1679)
• SHARP, JOHN (1645-1714)
• SHARP, RICHARD (1759-1835)
• SHARP, WILLIAM (1749-1824)
• SHARP, WILLIAM (1856-1905)

sharp-smelling gas which fumes strongly on exposure to air . It readily liquefies at 0° C. under a pressure of four atmospheres, the liquefied acid boiling at -34.14° C . (730.4 mm.); it can also be obtained as a solid melting at -50.8° C . It is readily soluble in water, one volume of water at Io° C. dissolving 425 volumes of the acid . The saturated aqueous solution is colourless and fumes strongly on exposure to air; after a time it darkens in colour owing to liberation of iodine .

The gas is readily decomposed by heat into its constituent elements . It is a powerful reducing agent, and is frequently employed for this purpose in organic chemistry; thus hydroxy acids are readily reduced on heating with the concentrated acid, and nitro compounds are reduced to amino compounds, &c . It is preferable to use the acid in the presence of amorphous phosphorus, for the iodine liberated during the reduction is then utilized in forming more hydriodic acid, and consequently the original amount of acid goes much further . It forms addition compounds with unsaturated compounds . It has all the characteristics of an acid, dissolving many metals with See also:

• EVOLUTION

evolution of hydrogen and formation of salts, called iodides . The iodides can be prepared either by direct union of iodine with a See also:

• METAL
• METAL (through Fr. from Lat. metallum, mine, quarry, adapted from Gr. µATaXAov, in the same sense, probably connected with ,ueraAAdv, to search after, explore, µeTa, after, aAAos, other)

metal, from hydriodic acid and a metal, oxide, hydroxide or carbonate, or by action of iodine on some metallic hydroxides or carbonates (such as those of potassium, sodium, See also:

• BARIUM (symbol Ba, atomic weight 137'37 [0=16])

barium, &c.; other products, however, are formed at the same time) . The iodides as a class resemble the chlorides and bromides, but are less fusible and volatile . See also:

• SILVER

Silver iodide, mercurous iodide, and mercuric iodide are insoluble in water; See also:

• LEAD
• LEAD (pronounced iced)

lead iodide is sparingly soluble, whilst most of the other metallic iodides are soluble . Strong heating decomposes the See also:

• MAJORITY (Fr. majorite; Med. Lat. majoritas; Lat. major, greater)

majority of the iodides . Nitrous acid and chlorine readily decompose them with liberation of iodine; the same effect being produced when they are heated with concentrated sulphuric acid and manganese dioxide . The soluble iodides, on the addition of silver nitrate to their nitric acid solution, give a yellow precipitate of silver iodide, which is insoluble in See also:

• AMMONIA (NH3)

ammonia solution . Hydriodic acid and the iodides may be estimated by See also:

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

conversion into silver iodide .

Iodine combines with chlorine to form iodine monochloride, See also:

• ICI

ICI, which may be obtained by passing dry chlorine over dry iodine until the iodine is completely liquefied, or according to R . See also:

• BUNSEN, CHRISTIAN CHARLES JOSIAS, BARON VON (1791-186o,)
• BUNSEN, ROBERT WILHELM VON (1811-1899)

Bunsen by boiling iodine with aqua regia and extracting with ether . It exists in two different crystalline forms, the more See also:

• STABLE

stable or a form melting at 27.2° C., and the less stable or # form melting at 13.9° C . It is readily decomposed by water . The trichloride, IC13, results from the action of excess of chlorine on iodine, or from iodic acid and hydrochloric acid, or by heating iodine pentoxide with phosphorus pentachloride . It crystallizes in See also:

• LONG, GEORGE (1800-1879)
• LONG, JOHN DAVIS (1838– )

long yellow needles and decomposes readily on heating into the monochloride and chlorine . It is readily soluble in water, but excess of water decomposes it . (See W . Stortenbeker, Zeit. phys . Chem., 1889, 3, p. it.) Iodine mono-chloride in glacial acetic acid solution was used by A . See also:

• MICHAEL
• MICHAEL (1596-1645)
• MICHAEL (Hebrew Sn,q, " Who is like God? ")

Michael and T . H .

See also:

• NORTON, CAROLINE ELIZABETH SARAH (18o8–1877)
• NORTON, CHARLES BOWYER ADDERLEY, 1ST BARON (1814–1905)
• NORTON, CHARLES ELIOT (1827-1908)
• NORTON, THOMAS (1532–1584)

Norton (See also:

• BEE (Sanskrit blza, AS. ben, Lat. apis)

Bee., 1876, 9, p . 1752) for the preparation of paraiodoacetanilide . Iodine Pentoxide, I205, the best-known oxide, is obtained as a 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 crystalline solid by heating iodic acid to 170° C.; it is easily soluble in water, combining with the water to regenerate iodic acid; and when heated to 300° C. it breaks up into its constituent elements . (see M . See also:

• GUICHARD, KARL GOTTLIEB (1724—1775)

Guichard, Compt. rend., 1909, 148, p . 925.) Iodine dioxide, I204, obtained by Millon, and reinvestigated by M . M . P . See also:

• MUIR, JOHN (1810-1882)
• MUIR, SIR WILLIAM (1819-1905)

Muir(Jour . Chem . Soc., 1909, 95, p . 656), is a See also:

• LEMON
• LEMON, MARK (1809-1870)

lemon-yellow solid obtained by acting on iodic acid with sulphuric acid, See also:

• OXYGEN (symbol 0, atomic weight 16)

oxygen being evolved .

By acting with See also:

• OZONE

ozone on a chloroform solution of iodine, F . Fichter and F . Rohner (Ber., 1909, 42, p . 4093) obtained a yellowish white oxide, of the See also:

• FORMULA
• FORMULA (Lat. diminutive of forma, shape, pattern, &c., especially used of rules of judicial procedure)

formula I409, which they regard as an iodate of tervalent iodine, Millon's oxide being considered a basic iodate . Although hypoiodous acid is not known, it is extremely probable that on adding iodine or iodine monochloride to a dilute solution of a caustic alkali, hypoiodites are forrned, the solution obtained having a characteristic smell of iodoform, and being of a See also:

• PALE (through Fr. pal, from Lat. palms, a stake, for paglus, from the stem pag- of pangere, to fix; " pole " is from the same original source)

pale yellow colour . It oxidizes arsenites, sulphites and thiosulphates immediately . The solution is readily decomposed on the addition of sodium or potassium bicarbonates, with liberation of iodine . The hypoiodite disappears gradually on See also:

• STANDING

standing, and rapidly on warming, being converted into iodate (see R . L . Taylor, Jour . Chem . Soc., 1897, 71, p .

725, and K . J . P . Orton, ibid. p . 83o) . The See also:

• PECULIAR

peculiar nature of the action between iodine and chlorine in aqueous solution has led to the See also:

• SUGGESTION

suggestion that the product is a See also:

• BASE

base, i.e. iodine hydroxide . Triiodine hydroxide, 13-0H, is obtained by oxidizing potassium iodide with sulphuric acid and potassium permanganate (A . Skrabal and F . Buchter, Chem . Zeit., 1909, 33, PP . 1184, 1193) . Iodic Acid, H103, can be prepared by dissolving iodine pentoxide in water; by boiling iodine with fuming nitric acid, 61+10HNO3= 6H103+1ONO+2H20; by decomposing barium iodate with the calculated quantity of sulphuric acid, previously diluted with water, or by suspending iodine in water and passing in chlorine, I2+5C12+ 6H2O =2HI03+10HC1 .

It is a white crystalline solid, easily soluble in water, the solution showing a strongly acid reaction with See also:

• LITMUS (apparently a corruption of lacmus, Dutch lacmoes, lac, lac, and moes, pulp, due to association with " lit," an obsolete word for dye, colour; the Ger. equivalent is Lac/emus, Fr tournesol)

litmus; the colour, however, is ultimately discharged by the See also:

• BLEACHING

bleaching See also:

• POWER [WILLIAM GRATTAN] TYRONE (1797-1841)

power of the See also:

• COMPOUND
• COMPOUND (from Lat. componere, to combine or put together)

compound . It is a most powerful oxidizing agent, phosphorus being readily oxidized to phosphoric acid, arsenic to arsenic acid, See also:

• SILICON [symbol Si, atomic weight 28.3 (0= 16)]

silicon at 250° C. to See also:

• SILICA

silica, and hydrochloric acid to chlorine and water . It is readily reduced, with separation of iodine, by sulphur dioxide, •hydriodic acid or sulphuretted hydrogen, thus: HI03+5H13H20+3r,; 2HI03+5SO2+4H20=5H2SO4+I2; 2H 103+5H2S = I2+5S+6H20 . The salts, known as the iodates, can be prepared by the action of the acid on a base, or sometimes by the oxidation of iodine in the presence of a base . They are mostly insoluble or only very slightly soluble in water . The iodates of the alkali metals are, however, readily soluble in water (except potassium iodate) . They are more easily reduced than the corresponding See also:

• CHLORATES

chlorates; an aqueous solution of hydriodic acid giving free iodine and a metallic oxide, whilst aqueous hydrochloric acid gives iodine trichloride, chlorine, water and a chloride . They are decomposed on heating, with liberation of oxygen, in some cases leaving a residue of iodide and in others a residue of oxide of the metal, with liberation of iodine as well as of oxygen . Periodic Acid, H104.2H2O, is only known in the hydrated form . It can be prepared by the action of iodine on perchloric acid, or by boiling normal silver periodate with water: 2AgIO4+4H20= Ag3H3I0,+HI04.2H20 . It is a colourless, crystalline, deliquescent solid which melts at 135° C., and at 14o° C. is completely decomposed into iodine pentoxide, water and oxygen . The periodates are a very complex class of salts, and may be divided into four classes, namely, See also:

• META

meta-periodates derived from the acid HI04; mesoperiodates from HI04•H20, See also:

• PARA
• PARA (officially BELEM; sometimes BELEM DO PARA)

para-periodates from HI04.2H20 and the diperiodates from 2HI04•1-120 (see C .

Kimmins, Jour . Chem . Soc., 1887, 51, p . 356) . Iodine has extensive applications in volumetric See also:

• ANALYSIS (Gr. avci and Meta, to break up into parts)

analysis, being used more especially for the determination of See also:

• COPPER (symbol Cu, atomic weight 63.1, H=1, or 63.6, O = 16)

copper . The atomic See also:

• WEIGHT

weight of iodine was determined by J . S . Stas, from the analysis of pure silver iodate, and by C . See also:

• MARIGNAC, JEAN CHARLES GALISSARD DE (1817-1894)

Marignac from the determinations of the ratios of silver to iodine, and of silver iodide to iodine; the mean value obtained for the atomic weight being 126.53 . G . P . See also:

• BAXTER, ANDREW (1686-1750)
• BAXTER, RICHARD (1615-1691)
• BAXTER, ROBERT DUDLEY (1827-1875)
• BAXTER, WILLIAM (1650-1723)

Baxter (Jour .

Amer . Chem . Soc., 1904, 26, p . 1577; 1905, 27, p . 876; 1909, 31, p . 201), using the method of Marignac, obtained the value 126.985 (O =16) . P . Kothner and E . Aeuer (Bee., 1904, 37, p . 2536; See also:

• ANN

Ann., 1904, 337, p . 362), who converted pure See also:

• ETHYL

ethyl iodide into hydriodic acid and subsequently into silver iodide, which they then analysed, obtained the value 126•o26 (H =1) • a discussion of this and other values gave as a mean 126.97 (0=16) . In See also:

• MEDICINE

medicine iodine is frequently applied externally as a See also:

• COUNTER

counter-irritant, having powerful antiseptic properties .

In the form of - certain salts iodine is very widely used, for See also:

• INTERNAL

internal See also:

• ADMINISTRATION (Lat. administrare, to serve)

administration in medicine and in the treatment of many conditions usually classed as surgical, such as the See also:

• BONE (a word common in various forms to Teutonic languages, in many of which it is confined to the shank of the leg, as in the German Bein)
• BONE, HENRY (1755-1834)

bone manifestations of See also:

• TERTIARY

tertiary syphilis . The most commonly used 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 is the iodide of potassium; the iodides of sodium and ammonium are almost as frequently employed, and those of calcium and See also:

• STRONTIUM [Symbol Sr, atomic weight 87.62 (0=16)]

strontium are in occasional use . The usual doses of these salts are from five to See also:

• THIRTY

thirty grains or more . Their pharmacological action is as obscure as their effects in certain diseased conditions are consistently brilliant and unexampled . Our See also:

• IGNORANCE (Lat. ignorantia, from ignorare, not to know); want of knowledge, a state of mind which in law has important consequences. A well-known legal maxim runs: ignorantia juris non excusat ("ignorance of the law does not excuse")

ignorance of their mode of action is cloaked by the See also:

• TERM

term deobstruent, which implies that they possess 31, 726 the power of See also:

• DRIVING (from " to drive," i.e. generally to propel, force along or in, a word common in various forms to the Teutonic languages)

driving out impurities from the See also:

• BLOOD

blood and tissues . Most notably is this the case with the poisonous products of syphilis . In its tertiary stages—and also earlier—this disease yields in the most rapid and unmistakable See also:

• FASHION (adapted from Fr. facon, agon, Lat. factio, making, facere, to do or make)

fashion to iodides; so much so that the administration of these salts is at present the best means of determining whether, for instance, a See also:

• CRANIAL

cranial See also:

• TUMOUR (Lat. tumor, a swelling)

tumour be syphilitic or not . No surgeon would think of operating on such a case until iodides had been freely administered and, by failing to cure, had proved the disease to be non-syphilitic . Another instance of this deobstruent power—" alterative," it was formerly termed—is seen in the case of chronic lead poisoning . The essential See also:

• PART

part of the medicinal treatment of this condition is the administration of iodides, which are able to decompose the insoluble albuminates of lead which have become locked up in the tissues, rapidly causing their degeneration, and to cause the See also:

• EXCRETION (Lat. ex, out of, cernere, cretum, to separate)

excretion of the poisonous metal by means of the See also:

• INTESTINE (Lat. intestinus, internal, usually in neuter plural intestina. from intus, within)

intestine and the kidneys . The following is a See also:

• LIST (O.E. lisle, a Teutonic word, cf. Dut. lust, Ger. Leiste, adapted in Ital. lista and Fr. lisle)
• LIST, FRIEDRICH (1789-1846)

list of the See also:

• PRINCIPAL

principal conditions in which iodides are recognized to be of definite value: metallic poisonings, as by lead and mercury, See also:

• ASTHMA (Gr. avBµa, gasping, whence lio-Ogaivw, I gasp for breath)

asthma, aneurism, arteriosclerosis, angina pectoris, See also:

• GOUT

gout, See also:

• GOITRE (from Lat. guttur, the throat; synonyms, Bronchocele, Derbyshire Neck)

goitre, syphilis, See also:

• HAEMOPHILIA

haemophilia, See also:

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

Bright's disease (nephritis) and See also:

• BRONCHITIS

bronchitis . Small quantities of the iodate (KI03) are a frequent impurity in iodide of potassium, and cause the congeries of symptoms known as iodism .

These comprise See also:

• DYSPEPSIA (from the Gr. prefix Sur-, hard, ill, and 'irirreiv, to digest)

dyspepsia, skin eruption and the manifestations which are usually identified with a " See also:

• COLD (in O. Eng. cald and ceald, a word coming ultimately from a root cognate with the Lat. gelu, gelidus, and common in the Teutonic languages, which usually have two distinct forms for the substantive and the adjective, cf. Ger. Kolte, kalt, Dutch koude

cold in the See also:

• HEAD (in 0. Eng. heafad; the word is common to Teutonic languages; cf. Dutch hoofd, Ger. Haupt, generally taken to be in origin connected with Lat. caput, Gr. KerbOvi7)
• HEAD, SIR EDMUND WALKER, BART
• HEAD, SIR FRANCIS BOND, BART

head." In many cases, as in syphilis, aneurism, lead poisoning, &c., the See also:

• LIFE

life of the patient depends on the free and continued use of the iodide, and this is best to be accomplished by securing an absolutely pure See also:

• SUPPLY (through Fr. from Lat. supplere, to fill up)

supply of the salt . Another often successful method of preventing the onset of symptoms of poisoning is to administer small doses of ammonium carbonate with the See also:

• DRUG
• DRUG (from Fr. drogue, a word common in Romance languages, cf. Span. and Ital. droga; the origin of the word is obscure, but may possibly be connected with Dutch droog, dry)

drug, thereby neutralizing the iodic acid which is liberated in the See also:

• STOMACH (Gr. vrbsaxos from arbga, a mouth)

stomach .