atomic See also:

• WEIGHT

weight 238.5 See also:

• atomic weight 238.5 URANIUM [symbol U (0=16)]

URANIUM [See also:

• SYMBOL (Gr. o-uµ(3oXov, a sign)

symbol U (0=16)]  , a metallic chemical See also:

• ELEMENT (Lat. elementum)

element . In 1789 See also:

• KLAPROTH, HEINRICH JULIUS (1783-1835)
• KLAPROTH, MARTIN HEINRICH (1743-1817)

Klaproth isolated from See also:

• PITCHBLENDE, or URANINITE

pitchblende a yellow See also:

• OXIDE

oxide which he viewed as the oxide of a new 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, which he named See also:

• URANIUM [symbol U, atomic weight 238.5 (0=16)]

uranium, after the newly discovered See also:

• PLANET (Gr. ssXavirrns, a wanderer)

planet of See also:

• HERSCHEL, CAROLINE LUCRETIA (1750-1848)
• HERSCHEL, SIR F
• HERSCHEL, SIR FREDERICK WILLIAM (1738-1822)
• HERSCHEL, SIR JOHN FREDERICK WILLIAM, BART

Herschel . By reducing the oxide with See also:

• CHARCOAL

charcoal at a high temperature, he obtained a product which he took to be metallic uranium . See also:

• BERZELIUS, JONS JAKOB (1779-1848)

Berzelius about 1823 found that the yellow oxide, when treated with excess of sulphuric See also:

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

acid, gave a sulphate not unlike the ferric 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 . He concluded that the uranium salt was Ur2033S03, where Ur203, according to his See also:

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

analysis, represents 864 parts of yellow oxide (0=16) . Like Fe203, the yellow oxide lost 48 parts of See also:

• OXYGEN (symbol 0, atomic weight 16)

oxygen per Ur203 (= 864 parts) as See also:

• WATER

water, while Ur2 = 816 parts of metal remained . These results were adopted until Peligot in 184o discovered that Berzelius's (and Klaproth's) metal contains oxygen, and that his (Ur2)03 really is (UsOs)•03=3U203, where U=12o is one See also:

• EQUIVALENT

equivalent See also:

• WEIGHT

weight of real uranium . Peligot's results, though called in question by Berzelius, have been amply confirmed by all subsequent investigators; only now, on theoretical grounds, first set forth by Mendeleeff, we See also:

• DOUBLE
• DOUBLE (from the Mid. Eng. duble, the form which gives the present pronunciation, through the Old Er. duble, from Lat. duplus, twice as much)

double Peligot's atomic weight, so that U now signifies 240 parts of uranium, while UO3 stands as the See also:

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

formula of the yellow oxide, and UO2 as that of Berzelius's metal . The only practically available raw material for the extraction of uranium is pitchblende (q.v.) . Pure pitchblende is U30s, which, in relatively See also:

• GOOD, JOHN MASON (1764-1827)

good specimens, forms some 8o% or more of the whole . It is remarkable as always containing See also:

• HELIUM (from Gr. i)Xcor, the sun)

helium (q.v.) and radioactive elements (see See also:

• RADIOACTIVITY

RADIOACTIVITY) . To See also:

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

extract the metal, the pitchblende is first roasted in 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 to remove the See also:

• ARSENIC (symbol As, atomic weight 75.0)

arsenic and See also:

• SULPHUR

sulphur .

In one See also:

• PROCESS

process the purified ore is disintegrated with hot nitric acid to produce nitrates, which are then converted into sulphates by evaporation with sulphuric acid . The sulphates are treated with water, which dissolves the uranium and other soluble salts, while See also:

• SILICA

silica, See also:

• LEAD
• LEAD (pronounced iced)

lead sulphate, &c., remain; these are removed by filtration . From the See also:

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

solution the arsenic, See also:

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

copper, &c., are precipitated by sulphuretted See also:

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

hydrogen as sulphides, which are filtered off . The filtrate contains the uranium as uranous and the See also:

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

iron as ferrous salt . These are oxidized and precipitated conjointly by excess of See also:

• AMMONIA (NH3)

ammonia . The precipitate, after having been collected and washed, is digested with a warm concentrated solution of ammonium carbonate, which dissolves the uranium as a yellow solution of ammonium uranate, while the hydrated oxide of iron, the alumina, &c., remain . These are filtered off hot, and the filtrate is allowed to cool, when crystals of the uranate See also:

• SEPARATE

separate out . The See also:

• MOTHER

mother liquor includes generally more or less of See also:

• NICKEL
• NICKEL (symbol Ni, atomic weight 58.68 (0=16))

nickel, See also:

• COBALT (symbol Co, atomic weight 59)

cobalt, See also:

• ZINC

zinc and other heavy metals, which, as See also:

• WOHLER, FRIEDRICH (1800-1882)

Wohler showed, can be removed as insoluble sulphides by the addition of ammonium sulphide; uranium, under the circumstances, is not precipitated by this reagent . The filtrate, on being boiled down, yields 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 of uranate . This uranate when Waited in a See also:

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

platinum crucible leaves a 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 oxide of the See also:

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

composition 30s, i.e. artificial pitchblende, which serves as a starting-point for the preparation of uranium compounds . The green oxide, as a See also:

• RULE

rule, requires to be further purified . One method for this purpose is to convert it into a solution of the nitrate UO2(NO3)2, and from it to precipitate the metal as oxalate by oxalic acid (Peligot) .

The latter (UO2•C204) yields a purer oxide, UO2, or, in the presence of See also:

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

air, U808, on ignition . Metallic uranium, as shown by Peligot, can be obtained by the reduction of a .mixture of dry chloride of See also:

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

potassium and dry uranous chloride, UCl4, with See also:

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

sodium at a 'red 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 . A better process is that of H . See also:

• MOISSAN, HENRI (1852-1907)

Moissan (Comp). rend., 1896, 122, p . 1o88), in which the oxide is heated with See also:

• SUGAR

sugar charcoal in the electric See also:

• FURNACE

furnace . Uranium is 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 malleable metal, which is See also:

• PRETTY

pretty hard, though softer than See also:

• STEEL, FLORA ANNIE (1847– )

steel . Its specificgravity has the high value 18.7; its specific heat is o•02765, which, according to See also:

• DULONG, PIERRE LOUIS (1785—1838)

Dulong and See also:

• PETIT, SIR DINSHAW MANECKJI, BART

Petit's See also:

• LAW
• LAW (0. Eng. lagu, M. Eng. lawe; from an old Teutonic root lag, " lie," what lies fixed or evenly; cf. Lat. lex, Fr. loi)
• LAW, JOHN (1671—1729)
• LAW, WILLIAM (1686-1761)

law, corresponds to U= 24o . It melts at See also:

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

bright redness . The compact metal when exposed to the air tarnishes only very slowly . The powdery metal when heated in air to 15o° or 17o° C. catches See also:

• FIRE (in O. Eng. f j'r; the word is common to West German languages, cf. Dutch vuur, Ger. Feuer; the pre-Teutonic form is seen in Sanskrit pu, pavaka, and Gr. irup; the ultimate origin is usually taken to be a root meaning to purify, cf. Lat. purus)

fire and See also:

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

burns brilliantly into U308; it decomposes water slowly at See also:

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

ordinary temperatures, but rapidly when boiling . It burns in oxygen at 17o°, in See also:

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

chlorine at 18o°°, in See also:

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

bromine at no, in See also:

• IODINE (symbol I, atomic weight '26.92)

iodine at 26o°, in sulphur at 500°, and combines with See also:

• NITROGEN [symbol N., atomic weight 14.01, 0=16]

nitrogen at about See also:

• I000

I000° . Dilute sulphuric acid attacks it hut slowly; hydrochloric acid, especially if strong, dissolves it readily, with the formation, more immediately, of a See also:

• HYACINTH (Gr. ualavOor)
• HYACINTH, or JACINTH

hyacinth-coloured solution of U2C18i which, however, readily absorbs oxygen from the air, with the formation of a green solution of UC14, which in its turn gradually passes into one of yellow uranyl salt, UO2•C12 .

Uranium is chemically related to See also:

• CHROMIUM (symbol Cr. atomic weight 52.1)

chromium, See also:

• MOLYBDENUM [symbol, Mo; atomic weight, 96 (0=16)]

molybdenum and See also:

• TUNGSTEN [symbol W, atomic weight 184.o (0=16)]

tungsten . If forms two See also:

• SERIES (a Latin word from serere, to join)

series of salts, one, the uranous compounds, are derived from the oxide UO2, the other, the uranyl compounds, contain the divalent See also:

• GROUP

group UO2 . Uranous Compounds.—Uranium dioxide, UO2 (Berzelius's metal), is a 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 to copper-coloured See also:

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

powder, obtained by See also:

• HEATING

heating U308 or uranyl oxalate in hydrogen . It fires when heated in air, and dissolves in acids to See also:

• FORM (Lat. forma)

form uranous salts . It may be obtained as See also:

• JET (Fr. jais, Ger. Gagat)

jet See also:

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

black octahedra (isomorphous with thoria) by See also:

• FUSION

fusion with See also:

• BORAX (sodium pyroborate or sodium biborate)

borax . Uranous See also:

• HYDRATE

hydrate is obtained as reddish-brown flakes by precipitating a uranous solution with See also:

• ALKALI

alkali . The solution in sulphuric acid deposits green crystals of the sulphate, U(SO4)2.8H20, on evaporation . Uranous chloride, UC14, was first prepared by Peligot by heating an intimate mixture of the green oxide and charcoal to redness in a current of dry chlorine; it is obtained as sublimate of black-green metallic-looking octahedra . The chloride is very hygroscopic . By heating in hydrogen it yields the trichloride, UC13, and by See also:

• DIRECT

direct See also:

• COMBINATION (Lat. combinare, to combine)

combination with chlorine the pentachloride, UCI5 . With hydroflouric acid it yields uranous fluoride, UF4, which forms double salts of the type MF.UF4 . Uranous bromide, UBr4, and uranous iodide, UI4, also exist .

Uranyl or Uranic Compounds.—Uranic oxide, UO3 or UO2.0, is obtained by heating uranyl nitrate to 250° as a yellow solid, insoluble in water, but soluble in acids with the formation of uranyl salts . Various hydrates have been described, but they cannot be formed by precipitating a uranyl salt with an alkali, this reagent giving rise to salts termed uranates . These salts generally resemble the bichromates; they are yellow in See also:

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

colour, insoluble in water, soluble in acids, and decomposed by heat . Sodium uranate, Na2U2O2, is used as a pigment for See also:

• PAINTING

painting on See also:

• GLASS
• GLASS (O.E. glees, cf. Ger. Glas, perhaps derived from an old Teutonic root gla-, a variant of glo-, having the general sense of shining, cf. " glare," " glow ")
• GLASS, STAINED

glass and See also:

• PORCELAIN

porcelain under the name of uranium yellow . It is manufactured by heating pitchblende with See also:

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

lime, treating the resulting See also:

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

calcium uranate with dilute sulphuric acid, and adding sodium carbonate in excess . Dilute sulphuric acid precipitates uranium yellow, Na2U2O7.6H2O, from the solution so obtained . Ammonium uranate heated to redness yields pure U308, which serves as a raw material for uranium compounds . Uranyl nitrate, UO2(NO3)2.6H20, is the most important uranium salt . It is obtained as See also:

• FINE

fine See also:

• LEMON
• LEMON, MARK (1809-1870)

lemon yellow deliquescent prisms by evaporating a solution of any of the oxides in nitric acid . By See also:

• ELECTROLYSIS (formed from Gr. Xbety, to loosen)

electrolysis it yields uranium dioxide as a pyrophoric powder, and peruranic hydroxide, U04.2H20, when treated with hydrogen peroxide . The latter gives rise to salts, the peruranates, e.g . (Na202)2U04.8H20 .

Uranyl nitrate is used in See also:

• PHOTOGRAPHY (Gr. bias, light, and ypa w, to write)
• PHOTOGRAPHY, CELESTIAL

photography, and also in See also:

• ANALYTICAL

analytical See also:

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

chemistry as a precipitant for phosphoric acid (as uranyl ammonium phosphate, Up02.NH4•PO4) . Uranyl chloride, UO2C12, is a yellow crystalline See also:

• MASS (O.E. maesse; Fr. messe; Ger. Messe; Ital. messa; from eccl. Lat. missa)
• MASS, IN

mass formed when chlorine is passed over uranium dioxide at a red heat . It is also obtained by dissolving the oxide in hydrochloric acid and evaporating . It forms double salts with metallic chlorides and with the hydrochlorides of organic bases . Uranyl sulphide, UO2S, is a black precipitate obtained by adding ammonium sulphide to a uranyl solution . Exposed to air this mixture is oxidized to the pigment uranium red, U2(NH4)2SO4, which is a fine See also:

• BLOOD

blood-coloured amorphous powder.' Analysis.—A borax See also:

• BEAD

bead dissolves uranium oxides in the reducing See also:

• FLAME (Lat. flamma; the root flag- appears in flagrare, to burn, blaze, and Gr. d, XEryew)

flame with a green, in the oxidizing flame with a yellow, colour . Solutions of uranyl salts (nitrate, &c.) behave to reagents as follows: sulphuretted hydrogen produces green uranous salt with precipitation of sulphur; sulphide of ammonium in neutral solutions gives a black precipitate of UO2S, which settles slowly and, while being washed in the See also:

• FILTER (a word common in various forms to most European languages, adapted from the medieval Lat. fi-ltrum, felt, a material used as a filtering agent)

filter, breaks up partially into hydrated UO2 and sulphur; ammonia gives a yellow precipitate of uranate of ammonia, characteristically soluble in hot carbonate of ammonia solution; prussiate of potash gives a brown precipitate which in See also:

• APPEARANCE (from Lat. apparere, to appear)

appearance is not unlike the precipitate produced by the same reagent in cupric salts .