See also:

• UREA, or CARBAMIDE, CO(NH2)2

UREA, or CARBAMIDE, CO(See also:

• NH2

NH2)2  , the See also:

• AMIDE

amide of carbonic See also:

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

acid, discovered in 1773 by H . M. v . See also:

• ROUELLE, GUILLAUME FRANCOIS (1703–1770)

Rouelle, is found in the urine of See also:

• MAMMALIA (from Lat. mamma, a teat or breast)

mammalia, birds and some See also:

• REPTILES (Lat. Reptilia, creeping things, from reptilis; ref ere, to creep; Gr. Ep7rety, whence the term " herpetology," for the science dealing with them)

reptiles; human urine contains approximately 2-3%, a grown See also:

• MAN
• MAN, ISLE OF (anc. Mona)

man producing about 30 grammes daily . It is also a constituent of the See also:

• BLOOD

blood, of See also:

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

milk, and other See also:

• ANIMAL
• ANIMAL (Lat. animalis, from anima, breath, soul)

animal fluids . Its See also:

• SYNTHESIS (Gr. a6vOeacs, from avvrcBivac, to put together)

synthesis in 1828 by F . See also:

• WOHLER, FRIEDRICH (1800-1882)

Wohler (Pogg . See also:

• ANN

Ann., 1828, 12, p . 253) is of theoretical importance, since it was the first organic See also:

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

compound obtained from inorganic materials . Wohler oxidized See also:

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

potassium ferrocyanide to potassium cyanate by fusing it with See also:

• LEAD
• LEAD (pronounced iced)

lead or See also:

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

manganese dioxide, converted this cyanate into ammonium cyanate by adding ammonium sulphate, and this on evaporation gives See also:

• UREA, or CARBAMIDE, CO(NH2)2

urea, thus: K4Fe(NC) — KCNO--sNH4CNO—>CO(See also:

• NH2

NH2)2• It may also be prepared by the See also:

• ACTION

action of See also:

• AMMONIA (NH3)

ammonia on carbonyl chloride, diethyl carbonate, chlorcarbonic ester or See also:

• URETHANE, NH2CO

urethane; by See also:

• HEATING

heating ammonium carbamate in a sealed See also:

• TUBE (Lat. tuba)

tube to 130-140° C.; by oxidizing potassium See also:

• CYANIDE

cyanide in acid See also:

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

solution with potassium permanganate (E . Baudrimant, Jahresb., 188o, p . 393); by the action of 50 % sulphuric acid on See also:

• CYANAMIDE

cyanamide: CN•NH2+H20=CO(NH2)z; by the action of mercuric See also:

• OXIDE

oxide on oxamide (A . See also:

• WILLIAMSON, ALEXANDER WILLIAM (1824–1904)
• WILLIAMSON, SIR JOSEPH (1633–1701)
• WILLIAMSON, WILLIAM CRAWFORD (18r6–1895)

Williamson) : (CONH2)z+HgO= CO(NH2)2+ Hg+C.O2; by decomposing potassium cyanide with a dilute solution of See also:

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

sodium hypochlorite, followed by adding ammonium sulphate (A .

Reychler, See also:

• BULL
• BULL, GEORGE (1634–1710)
• BULL, JOHN (c. 1562–1628)
• BULL, OLE BORNEMANN (18ro-188o)

Bull . See also:

• SOC

Soc . Chim., 1893 [31, 9, p . 427); and by oxidation of uric acid . It may be obtained from urine by evaporating to dryness on the See also:

• WATER

water See also:

• BATH
• BATH, THOMAS THYNNE
• BATH, WILLIAM

bath, taking up the See also:

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

residue in See also:

• ABSOLUTE (Lat. absolvere, to loose, set free)

absolute See also:

• ALCOHOL

alcohol and evaporating the alcoholic solution to dryness again . The residue is then dissolved in water, decolorized by animal See also:

• CHARCOAL

charcoal and saturated at 5o° C. with oxalic acid . The urea oxalate is recrystallized and decolorized and finally decomposed by See also:

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

calcium carbonate (J . J . See also:

• BERZELIUS, JONS JAKOB (1779-1848)

Berzelius, Pogg . Ann., 183o, 18, p . 84) . As an alternative method, A .

N . E . Millon (Ann. chim. phys [2], 8, p . 235) concentrates the urine and precipitates the urea by nitric acid . The precipitate is dissolved in boiling water, decolorized by potassium permanganate and decomposed by See also:

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

barium carbonate . The solution is then evaporated to dryness and extracted by alcohol . Urea crystallizes in See also:

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

long needles or prisms which melt at 132° C. and See also:

• SUBLIME (Lat. sublimis, exalted)

sublime when heated in vacuo . It is readily soluble in water and in alcohol, but is insoluble in See also:

• CHLOROFORM (trichlor-methane), CHC13

chloroform and See also:

• ETHER, (C2H5)2O

ether . When heated above its melting-point, it yields ammonia, cyanuric acid, biuret and ammelide . On warming with sodium, it yields cyanamide . Dry See also:

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

chlorine See also:

• GAS

gas passed into melted urea decomposes it with formation of cyanuric acid and ammonium chloride, See also:

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

nitrogen and ammonia being simultaneously liberated . Alkaline hypobromites or hypochlorites or nitrous acid decompose urea into See also:

• CARBON (symbol C, atomic weight 12)

carbon dioxide and nitrogen .

It is also decomposed by warm aqueous solutions of See also:

• CAUSTIC (Gr. rcavvraubs, burning)

caustic alkalis, with See also:

• EVOLUTION

evolution of ammonia and carbon dioxide . When heated with alcohol in sealed tubes, it yields carbamic See also:

• ESTERS

esters; with alcohol and carbon bisulphide at too° C., carbon dioxide is liberated and ammonium sulphocyanide is formed . Acid potassium permanganate oxidizes it to carbon dioxide and nitrogen . It acts as a monacid See also:

• BASE

base . Urea may be recognized by its crystalline oxalate and nitrate, which are produced on adding oxalic and nitric acids to concentrated solutions of the base; by the 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 precipitate formed on adding mercuric nitrate to the neutral aqueous solutions of urea; and by the so-called " biuret " reaction . In this reaction urea is heated in a dry tube until it gives off ammonia freely; the residue is dissolved in water, made alkaline with caustic soda, and a drop of See also:

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

copper sulphate solution is added, when a See also:

• FINE

fine See also:

• VIOLET

violet-red coloration is produced . Several methods are employed for the quantitative estimation of urea . R . See also:

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

Bunsen (Ann., 1848, 65, p . 875) heated urea with an ammoniacal solution of barium chloride to 220° C., and converted the barium carbonate formed into barium sulphate, which is then weighed (see also E . Pfluger and K . Bohland, Zeit. f. anal .

Chem., 1886, 25, p . 599; K . A . H . Morner, ibid., 1891, 30, p . 389) . Among the volumetric methods used, the one most commonly employed is that of W . Knop (ibid., 187o, 9, p . 226), in which the urea is decomposed by an alkaline hypobromite and the evolved nitrogen is measured (see A . H . See also:

• ALLEN, BOG OF
• ALLEN, ETHAN (1739–1789)
• ALLEN, GRANT CHARLES GRANT BLAIRFINDIEI, (1848–1899)
• ALLEN, JAMES LANE (1850– )
• ALLEN, JOHN (1476–1534)
• ALLEN, or ALLEYN, THOMAS (1542-1632)
• ALLEN, WILLIAM (1532-1594)
• ALLEN, WILLIAM FRANCIS (183o-1889)

Allen, Commercial Organic See also:

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

Analysis) . J. v .

See also:

• LIEBIG, JUSTUS VON, BARON (1803-1873)

Liebig (Ann., 1853, 85, p . 289) precipitates dilute solutions of urea with a dilute See also:

• STANDARD
• STANDARD, BATTLE OF THE

standard solution of mercuric nitrate, using alkaline carbonate as See also:

• INDICATOR (from Lat. indicare, to point out)

indicator . In this See also:

• PROCESS

process See also:

• PHOSPHATES

phosphates must be absent, and the nitric acid liberated during the reaction should be neutralized as soon as possible . Chlorides also prevent the formation of the precipitate until enough of the See also:

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

mercury solution has been added to convert them into mercuric chloride (see also E . Pfluger, Zeit. f. anal . Chem., 188o, 19, p . 378) . E . Riegler (ibid., 1894, 33, p . 49) decomposes urea solutions by means of mercury dissolved in nitric acid, and See also:

• MEASURES

measures the evolved gas . Urea chlorides are formed by the action of carbonyl chloride on ammonium chloride (at 400° C.), or on salts of See also:

• PRIMARY

primary See also:

• AMINES

amines . They are readily hydrolysed by water, and combine with bases to See also:

• FORM (Lat. forma)

form alkyl ureas, and with See also:

• ALCOHOLS
• ALCOHOLS, ALDEHYDES AND
• ALCOHOLS, BENZYL ALCOHOL, BUTYL ALCOHOLS, METHYL ALCOHOL

alcohols to form carbamic esters .

Substituted urea chlorides are formed by the See also:

• DIRECT

direct action of chlorine (F . D . Chattaway and D . F . S . Wunsch, Jour . Chem . Soc., 1909, 95, p . 129) . Urea chloride, NH2•CO•Cl (L . Gattermann, Ann., 1888, 244, p . 30), melts at 5o° C. and boils at 61-62° C .

In the presence of anhydrous See also:

• ALUMINIUM (symbol Al; atomic weight 27.0)

aluminium chloride it reacts with aromatic See also:

• HYDROCARBONS

hydrocarbons to form the amides of aromatic acids . Nitro-urea, See also:

• H2N

H2N•CO•NH•NO2, prepared by adding urea nitrate to well-cooled concentrated sulphuric acid (J . Thiele and A . See also:

• LACHMANN, KARL KONRAD FRIEDRICH WILHELM (1793-1851)

Lachmann, Ann., 1895, 288, p . 281), is a crystalline See also:

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

powder, soluble in water, and which decomposes on heating . It is a .strong acid and is See also:

• STABLE

stable towards oxidizing agents . Diazomethane converts it into the 794 methyl derivatives of isocyanic acid, and nitramide, NH2NO2 . Amidourea, or semicarbazide, NH2•CO•NH•NH2, is best prepared from See also:

• HYDRAZINE (DIAMIDOGEN), N2H4

hydrazine sulphate and potassium cyanate (J . Thiele and O . Stange, Ber., 1894, 27, p . 31) . It may also be obtained by reducing nitrourea in acid solution with See also:

• ZINC

zinc dust .

It crystallizes in prisms, which melt at 96° C., and are easily soluble in water . It reduces See also:

• FEHLING, HERMANN VON (1812—1885)

Fehling's solution in the 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 . It reacts with carbonyl compounds, giving semi-carbazones, and in consequence is frequently used for characterizing such substances . Hydroxy-urea, NH2•CO•NH•OH, is produced from See also:

• HYDROXYLAMINE, NH2OH

hydroxylamine and cyanic acid (W . F . Dresler and R . See also:

• STEIN, CHARLOTTE VON (1742-1827)
• STEIN, HEINRICH FRIEDRICH KARL, BARON VOM

Stein, Ann., 1869, 15o, p . 242), or from ammonium hypo-See also:

• CHLORITE

chlorite and potassium cyanate (A . Hantzsch, Ann., 1898, 299, p . 99) . It crystallizes in needles, which melt at 128-13o° C., and is decomposed on long heating . It is readily soluble in water and reduces warm See also:

• SILVER

silver solutions .

Hyponitrous acid is formed by passing nitrous fumes into its methyl alcohol solution . Alkyl ureas are formed by the action of primary or secondary amines on isocyanic acid or its esters: See also:

• CONH

CONH+NH2R= R.NHCONH2; CONR+NHR2=NR2•CO•NHR; by the action of carbonyl chloride on amines: COC12+2NHR2=CO(NR2)2+2HCI; and in the See also:

• HYDROLYSIS (Gr. 6Swp, water, Anew, to loosen)

hydrolysis of many ureides . The tetra-alkyl derivatives are liquids, the See also:

• REMAINDER, REVERSION

remainder being solids . Hydrolysis by alkalis decomposes them into carbon dioxide, amines and ammonia . The symmetrically substituted ureas are generally tasteless, while the asymmetrical derivatives are sweet . For example, aa-dimethyl urea is sweet, a3-dimethyl urea is tasteless; p-phenetol carbamide or dulcin, N H2• CO • NH • See also:

• C6H

C6H a• OC2H5, is sweet, while the di-p-phenetol carbamide, CO(NH•See also:

• C6H4
• C6H4(CH213r)2

C6H4.0C2H5)2, is tasteless . The derivatives of urea containing acid radicles are known as ureides . Those derived from monobasic acids, obtained by the action of acid chlorides or anhydrides on urea, decompose on heating and do not form salts . Those containing more than one acyl See also:

• GROUP

group are formed by the action of carbonyl chloride on acid amides: COC12+2CH3CONH2 = CO(NHCOCHa)2+2HCI . Acetyl urea, NH2•CO•NH•000H3, formed by the action of acetic anhydride on urea, crystallizes in needles which melt at 212 ° C. and, on heating, strongly decomposes into acetamide and cyanuric acid . Methyl acetyl urea, CH2NH•CO•NH000H3, is formed by the action of potash on a mixture of See also:

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

bromine (1 mol.) and acetamide (2 See also:

• MOLE
• MOLE, LOUIS MATHIEU, COMTE (1781—1855)
• MOLE, MATHIEU (1584—1656)

mole.) (A . W. v .

See also:

• HOFMANN, AUGUST WILHELM VON (1818-1892)
• HOFMANN, JOHANN CHRISTIAN KONRAD VON (1810—1877)
• HOFMANN, MELCHIOR (c. 1498—1543-4)

Hofmann, Ber., 1881, 14, p . 2725), or of methylamine on acetylurethane (G . 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, Jour . Chem . Soc., 1898, 73, p . 364) . When heated with water it is decomposed into carbon dioxide, ammonia, methylamine and acetic acid . Bromural or a-bromisovaleryl urea, NH2•CO•NH•CO•CHBr•CH(See also:

• CH3

CH3)2, has been introduced as an hypnotic; its action is mild, and interfered with by the presence of See also:

• PAIN (from Lat. poena, Gr. robin, penalty, that which must be paid: O. Fr. peine)
• PAIN, BARRY (1867– )

pain, cough or See also:

• DELIRIUM (a Latin medical term for madness, from delirare, to be mad, literally to wander from the lira, or furrow)

delirium . The ureides of oxy-acids and dibasic acids form closed See also:

• CHAIN (through the O. Fr. citable, chcene, &c., from Lat. catena)

chain compounds (see See also:

• ALLANTOIN, C4H6N4O3

ALLANTOIN; ALLOXAN; See also:

• HYDANTOIN (glycolyl urea), C3H4N202

HYDANTOIN; See also:

• PURIN, C5H4N4

PURIN) . Parabanic acid (oxalyl urea), CO[NH•CO]2, is formed by oxidizing uric acid ; or by condensing oxalic acid and urea in the presence of See also:

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

phosphorus oxychloride . It crystallizes in needles and is readily hydrolysed by alkalis . It behaves as a monobasic acid and forms unstable salts .

When heated with urea, it forms oxalyl diureide, H2N•CO•CO•NH•CO•NH•CO•NH2 . Dimethylparabanic acid (cholesterophane), CO[NCH3•CO]2, is formed by oxidizing See also:

• CAFFEINE, or THEINE (1.3.7 trimethyl 2 . 6 dioxypurin)

caffeine or by methylating parabanic acid . It crystallizes in plates, which melt at 145.5° C., and is soluble in cold water . Hydrochloric acid at 200° C. decomposes into oxalic acid, carbon dioxide and methylamine, whilst an alcoholic solution of a caustic See also:

• ALKALI

alkali gives dimethyl urea and oxalic acid . Barbituric acid (malonyl urea), See also:

• CH2
• CH2(OH)

CH2[CO•NH]CO.2H2O, formed by condensing malonic acid with urea (E . Grimaux, Bull . Soc . Chem., 1879, 31, 146), crystallizes in prisms, which decompose on heating . It yields a nitroso derivative, is nitrated by nitric acid to dilituric acid and brominated by bromine . It is a dibasic acid . Veronal (q.v.) is diethyl malonyl urea . For isobarbituric acid see T .

B . See also:

• JOHNSON, ANDREW
• JOHNSON, ANDREW (1808–1875)
• JOHNSON, BENJAMIN (c. 1665-1742)
• JOHNSON, EASTMAN (1824–1906)
• JOHNSON, REVERDY (1796–1876)
• JOHNSON, RICHARD (1573–1659 ?)
• JOHNSON, RICHARD MENTOR (1781–1850)
• JOHNSON, SAMUEL (1709-1784)
• JOHNSON, SIR THOMAS (1664-1729)
• JOHNSON, SIR WILLIAM (1715–1774)
• JOHNSON, THOMAS

Johnson and E . V . McCollum, Jour . Biol . Chem., 1906, 1, p . 437 . Tartronyl urea (dialuric acid), CO[NH•CO]CH•OH, formed by the reduction of alloxan (J. v . Liebig and F . Wohler, Ann., 1838, 26, p . 276), or of See also:

• ALLOXANTIN, C8H4N407

alloxantin (A . See also:

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

Baeyer, Ann., 1863, 127, p .

12), crystallizes in needles or prisms and possesses a very acid reaction . It becomes red on exposure, and in the moist See also:

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

condition absorbs See also:

• OXYGEN (symbol 0, atomic weight 16)

oxygen from the See also:

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

air, giving alloxantin . Allophanic acid, NH2•CO•NH•See also:

• CO2H

CO2H, is not known in the See also:

• FREE

free See also:

• STATE
• STATE, GREAT OFFICERS OF

state, as when liberated from its salts, it is decomposed into urea and carbon dioxide . Its esters are formed by passing the vapours of cyanic acid into alcohols (W . Traube, Ber., 1889, 22, p .