PRUSSIC See also:

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

ACID, or HYDROCYANIC ACID, HCN  , an organic See also:

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

acid first prepared in 1782–1783 by C . See also:

• SCHEELE, KARL WILHELM (1742-1786)

Scheele and subsequently examined by J . See also:

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

Gay-Lussac . It is See also:

• PRESENT

present in varying amounts in certain See also:

• PLANTS

plants, being a product of the See also:

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

hydrolysis of the cyanogenetic glucosides, e.g. See also:

• AMYGDALIN (from the Gr. aµurySaXrt, almond), C2

amygdalin (q.v.) . It may be prepared by See also:

• HEATING

heating a mixture of See also:

• CYANOGEN (Gr. ebavos, blue 'yevvav, to produce), C2N2

cyanogen and See also:

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

hydrogen to 500 -550° C . (M . See also:

• BERTHELOT, MARCELLIN PIERRE EUGENE (1827–1907)

Berthelot, See also:

• ANN

Ann. chim. phys., 1879 (5), 18, p . 38o); by passing See also:

• INDUCTION (from Lat. inducere, to lead into; cf. Gr. ilrayu yli)

induction See also:

• SPARKS, JARED (1789-1866)

sparks through a mixture of See also:

• ACETYLENE

acetylene and See also:

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

nitrogen; by the dry See also:

• DISTILLATION (from the Lat. distillare, more correctly destillare, to drop or trickle down)

distillation of ammonium formate; by the decomposition of the See also:

• SIMPLE

simple cyanides with See also:

• MINERAL

mineral acids; and by distilling See also:

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

potassium ferrocyanide with dilute sulphuric acid (F . See also:

• WOHLER, FRIEDRICH (1800-1882)

Wohler, Ann., 185o, 73, p . 219), the anhydrous acid being obtained by fractional distillation of the aqueous distillate, See also:

• SPECIAL

special precautions being necessary owing to the excessively poisonous nature of the See also:

• FREE

free acid: K4Fe(NC)s+3H2SO4 = 2K2SO4+FeSO44-6HCN . The free acid is a colourless liquid with a See also:

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

smell resembling See also:

• BITTER, KARL THEODORE FRANCIS (1867– )

bitter almonds; it boils at 26.1° C., and may be solidified, in which See also:

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

condition it melts at -14° C . It See also:

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

burns with a See also:

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

blue See also:

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

flame, and is readily soluble in See also:

• WATER

water, but the See also:

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

solution is unstable and decomposes on See also:

• STANDING

standing, giving amorphous insoluble substances, and ammonium formate, oxalic acid, &c .

An aqueous solution of hydrogen peroxide converts it into oxamide, (CONH2)2, and reduction by See also:

• ZINC

zinc and hydrochloric acid gives methylamine . The anhydrous acid combines with hydrochloric, hydrobromic and hydriodic acids to See also:

• FORM (Lat. forma)

form crystalline addition products, which are decomposed by water MO the formation of the corresponding ammonium 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 and formic acid . It combines with See also:

• ALDEHYDES

aldehydes and See also:

• KETONES

ketones to form the nitriles of oxy-acids, for example, CH3CHO+HCN=CH3CH(OH)(CN) . It is a very weak monobasic acid, and the aqueous solution has a very See also:

• LOW, SETH (1850- )
• LOW, WILL HICOK (1853- )

low electric conductivity . Cyanides.—The salts of this acid, known as cyanides, may be prepared by the See also:

• ACTION

action of cyanogen or of gaseous hydro-cyanic acid on 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; by heating the See also:

• CARBONATES

carbonates or hydro-oxides of the See also:

• ALKALI

alkali metals in a current of hydrocyanic acid; by heating alkaline carbonates with See also:

• CARBON (symbol C, atomic weight 12)

carbon in the presence of free nitrogen: BaCO3 + 4C + N2 = Ba(NC)2 -]- 3C0; by ignition of nitrogenous organic substances in the presence of alkaline carbonates or hydroxides; or by processes of 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 decomposition . The alkali and alkaline See also:

• EARTH
• EARTH (a word common to Teutonic languages, cf. Ger. Erde, Dutch aarde, Swed. and Dan. jord; outside Teutonic it appears only in the Gr. 'pq'e, on the ground; it has been connected by some etymologists with the Aryan root ar-, to plough, which is seen in
• EARTH, FIGURE OF
• EARTH, FIGURE OF THE

earth cyanides are soluble in water and in See also:

• ALCOHOL

alcohol, and their aqueous solution, owing to hydrolytic See also:

• DISSOCIATION

dissociation, possesses an alkaline See also:

• CHARACTER (Gr. xapareri7p, from xap&crew, to scratch)

character . When heated in contact with See also:

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

air they undergo a certain amount of oxidation, being converted to some extent into the corresponding cyanate . The cyanides of other metals are decomposed by 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, frequently with liberation of cyanogen . The cyanides are usually reducing agents . Those of the heavy metals are mostly insoluble in water, but are soluble in a solution of potassium See also:

• CYANIDE

cyanide, forming more or less See also:

• STABLE

stable double salts, for example KAg(NC)2, KAu(NC)2 . See also:

• LEAD
• LEAD (pronounced iced)

Lead cyanide, Pb(NC)2, however, does not form such a salt, and is insoluble in potassium cyanide solution . Ammonium cyanide, NH4NC, 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 solid found to some slight extent in See also:

• ILLUMINATING

illuminating See also:

• GAS

gas, is easily soluble in water and alcohol, and is very poisonous .

Its vapour is inflammable . It is obtained by passing See also:

• AMMONIA (NH3)

ammonia gas over hot See also:

• COAL

coal; by subliming a mixture of ammonium chloride and potassium cyanide; by passing a mixture of ammonia gas and See also:

• CHLOROFORM (trichlor-methane), CHC13

chloroform vapour through a red hot See also:

• TUBE (Lat. tuba)

tube; and by heating a mixture of ammonia and carbon monoxide: CO+2NH3=NH4NC+H20 . See also:

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

Barium cyanide, Ba(NC)2, pre-pared by the action of potassium cyanide on baryta, or by passing air over a heated mixture of barium carbonate and coal, is a white solid, which when heated with water to 300° C. loses the whole of its nitrogen in the form of ammonia . Mercuric cyanide, Hg(NC)2, is a sparingly soluble salt formed by dissolving precipitated mercuric See also:

• OXIDE

oxide in hydrocyanic acid, or by boiling potassium ferrocyanide with mercuric sulphate and water: 2K4Fe(NC)6+3HgSO4=3Hg(NC)2+ 3K2SO4+K2Fe[Fe(NC)e]• Its aqueous solution is not an electrolyte, and consequently does not give the reactions of the See also:

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

mercury and cyanogen ions . When heated it yields mercury, cyanogen and paracyanogen . See also:

• SILVER

Silver cyanide, AgNC, is formed as a white precipitate by adding potassium cyanide to silver nitrate solution; or better, by adding silver nitrate to potassium silver cyanide, KAg(NC)2, this double cyanide being obtained by the addition of one molecular proportion of potassium cyanide to one molecular proportion of silver nitrate, the white precipitate so formed being then dissolved by adding a second See also:

• EQUIVALENT

equivalent of potassium cyanide . On concentration the double salt separates as hexagonal tables . Dilute mineral acids decompose it with the formation of insoluble silver cyanide and hydrocyanic acid: KNC•AgNC+HNO3=HCN+ KNO3+AgNC . A boiling solution of potassium chloride with the double cyanide gives silver chloride and potassium cyanide . Potassium cyanide, KNC, and See also:

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

sodium cyanide, NaNC, are two of the most important of the salts of hydrocyanic acid, the former being manufactured in large quantities for See also:

• CONSUMPTION (Lat. consumere)

consumption in the extraction of See also:

• GOLD
• GOLD [symbol Au, atomic weight 195.7(H = 1),197.2(0 =16)]

gold (q.v.) . Potassium cyanide may be obtained by fusing potassium ferrocyanide either alone—K4Fe(NC)6=4KNC+ FeC2+N2—or with potassium carbonate [V . See also:

• ALDER

Alder, See also:

• ENGLISH

English patent 1353 (1900)]; in the latter See also:

• CASE
• CASE, JOHN (d. 1600)

case the See also:

• CHIEF (from Fr. chef, head, Lat. caput)

chief reaction probably is: K4Fe(NC)6 + K2CO3 = 4KNC + 2KOCN + CO + Fe ; more potassium ferrocyanide is- occasionally added in small quantities, 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 decompose the cyanate formed; 2KOCN-{-2K4Fe(NC)6= ioKNC + 2FeO + 4C + 2N2; 2FeO + 2C = 2C0 + 2Fe .

The re-action is accompanied by much frothing, and the whole is filtered when in a See also:

• STATE
• STATE, GREAT OFFICERS OF

state of tranquil See also:

• FUSION

fusion . Rossler and Hasslacher prepare the double potassium sodium cyanide by fusing potassium ferrocyanide with sodium, the product of fusion being extracted with water and the solution evaporated: K4Fe(NC)6 + 2Na = Fe+ 4KNC•2NaNC . This See also:

• PROCESS

process gives a product free from cyanate, which was always formed in the older fusion processes . Many other processes have been devised . D . T . See also:

• PLAYFAIR, JOHN (1748-1819)
• PLAYFAIR, LYON PLAYFAIR

Playfair [Eng. pat . 7764 (1890)1 decomposes sulphocyanides by fusing with zinc: the zinc is heated with a small quantity of carbon and when completely fused potassium sulphocyanide is added, the See also:

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

mass being well stirred and heated until', it thickens and begins to turn red; finally it is allowed to cool out of contact with air, lixiviated with water, the solution decanted, and evaporated to a 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 in vacuo . The potassium sulphocyanide is obtained from ammonium sulphocyanide, which is formed by washing crude coal gas with watercontaining suspended See also:

• SULPHUR

sulphur . Various processes involving the use of atmospheric nitrogen have been devised, but in most cases they do not yield See also:

• GOOD, JOHN MASON (1764-1827)

good results . More successful results are obtained by the use of ammonia . The Stassfurter Chem .

Fabrik [Eng. pat . 9350–2 (1900)] pass ammonia over a mixture of alkali or alkaline carbonate and See also:

• CHARCOAL

charcoal, first at a dull red heat and then at a See also:

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

bright red heat : KHO + NH3 + C = KNC + See also:

• H2O (combined)

H2O + H2 . H . Y . Castner [Fr. pat . 242938 (1894)] passes anhydrous ammonia over heated sodium to form sodamide, which is then brought in a molten condition into contact with carbon: NaNH2+C=NaNC+H2• The Deutsche Gold and Silber Scheide Anstalt [Eng. pat . 3328, 3329 (1901)] prepare sodium See also:

• CYANAMIDE

cyanamide by melting sodium with carbons or some See also:

• HYDROCARBON

hydrocarbon, and passing ammonia over the melt at from 400°--600° C . The temperature is then raised to 700°–800° C., and the sodium cyanamide in contact with the residual carbon forms sodium cyanide . H . W . See also:

• CROWTHER, SAMUEL ADJAI (18o9?—1895)

Crowther and E . C .

Rossiter (Journ . See also:

• SOC

Soc . Chem . Ind., 1893, 13, p . 887) See also:

• DIGEST

digest carbon bisulphide with ammonia and See also:

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

lime in quantities slightly in excess of those demanded by the following See also:

• EQUATION (from Lat. aequatio, aequare, to equalize)

equation: 2CS2 + 2NH3 + 2Ca(OH)2 = Ca(SCN)2 + Ca(SH)2+4H2O; the product is then treated with a current of carbon dioxide. See also:

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

calcium carbonate being precipitated, sulphuretted hydrogen escaping, and calcium sulphocyanide remaining in solution . The sulphocyanide is converted into the potassium salt by adding potassium sulphate, and finally desulphurized by lead, zinc, or See also:

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

iron . Potassium cyanide is an excessively poisonous, colourless, de-liquescent solid; it is readily soluble in water, but almost insoluble in See also:

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

absolute alcohol . It is stable in dry air, but is easily oxidized when fused, in which condition it is a powerful reducing See also:

• AGENT (from Lat. agere, to act)

agent . It dissolves gold (q.v.) in the presence of water and atmospheric See also:

• OXYGEN (symbol 0, atomic weight 16)

oxygen . It is also largely used by the jeweler, electroplates and photographer . Double Cyanides.—The double cyanides formed by the solution of the cyanide of a heavy metal in a solution of potassium cyanide are decomposed by mineral acids with liberation of hydro-cyanic acid and formation of the cyanide of the heavy metal . Besides these, other double cyanides are known which do not suffer such decomposition, the heavy metal present being combined with the cyanogen See also:

• RADICAL (Lat. radix, a root)

radical in the form of a complexion .

The most important members of these classes are the ferro- and See also:

• FERN (from O. Eng. fearn, a word common to Teutonic languages, cf. Dutch varen, and Ger. Farn; the Indo-European root, seen in the Sanskrit parna, a feather, shows the primary meaning; cf. Gr. rmep6 , feather, rTepis, fern)

fern'-cyanides and the nitroprussides . Potassium ferrocyanide, K4Fe(NC)6, (yellow prussiate of potash), was first obtained by decomposing Prussian blue with See also:

• CAUSTIC (Gr. rcavvraubs, burning)

caustic potash: Fe4[Fe(NC)6]3 + 12KHO = 3K4Fe(NC)s +4Fe(OH)3; it may be also obtained by warming a solution of ferrous sulphate with an excess of potassium cyanide: FeSO4+6KNC=K4Fe(NC)e+ K2SO4 . The older processes for the commercial preparation of this salt, which wee based on the ignition of nitrogenous substances with an alkaline carbonate and carbon, have almost all been abandoned, since it is more profitable to prepare the salt from the by-products obtained in the manufacture of illuminating gas . W . Fowlis [Eng. pat . 9474 (1892)] passes the gas (after freeing it from ammonia) through a solution of potassium carbonate containing ferric oxide or ferrous carbonate (actually ferrous sulphate and potassium carbonate) in suspension; the sulphuretted hydrogen in the gas probably converts the iron salts into ferrous sulphide which then, in the presence of the hydrocyanic acid in the gas, and the alkaline carbonate, forms the ferrocyanide, thus: FeS+6HCN+ 2K2CO3 = K4Fe(NC)6 + H2S + 2CO2 + 2H20 . The salt is re-covered by See also:

• CRYSTALLIZATION

crystallization . The process is not very efficient, since the solutions are too dilute and large quantities of liquid have to be handled . A large quantity of the salt is now prepared from the " spent oxide " of the gas See also:

• WORKS

works, the cyanogen compounds formed in the manufacture of the gas combining with the ferric oxide in the purifiers to form insoluble iron ferrocyanides . The soluble salts are removed by lixiviation, and the See also:

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

residue is boiled with lime to form the soluble calcium ferrocyanide, which is finally converted into the potassium salt by potassium chloride or carbonate . The salt crystallizes in large yellow plates, containing three molecules of water of crystallization . It is soluble in water, but insoluble in alcohol .

It is not poisonous . When fused with potassium carbonate it yields potassium cyanide; warmed with dilute sulphuric acid it yields hydrocyanic acid, but with concentrated sulphuric acid it yields carbon monoxide: 6H20 + K4Fe(NC)s + 6H2SO4 = 2K2SO4 + FeSO4 + 3(NH4)2SO4 + 6C0 . Oxidizing agents (Cl, Br, H202, &c.) convert it into potassium ferricyanide (see below), a similar result being attained by the See also:

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

electrolysis of its aqueous solution: 2K4Fe(NC)s + 2H20 = 2KOH + H2 + 2K3Fe(NC)6 . ' Potassium ferrocyanide may be estimated quantitatively in acid solution by oxidation to ferricyanide by potassium permanganate (in See also:

• ABSENCE (Lat. absentia)

absence of other reducing agents): 5K4Fe(NC)i + KMnO4 + 4H2SO4= 5K1Fe(NC)6 + 3K2SO4+MnSO4+4H20 . Hydroferrocyanic acid, H4Fe(NC)e, is best obtained by decomposing the lead salt with sulphuretted hydrogen under water, or by passing hydrochloric acid gas into a concentrated See also:

• ETHER, (C2H5)2O

ether solution of the potassium salt . In the latter case the precipitate is dissolved in water, reprecipitated by ether, and washed with ether-alcohol . It is a tetrabasic acid, of markedly acid character, and readily considered as derivatives of thus yet unknown isohydrocyanic acid HNC . decomposes carbonates and acetates . It dissolves unchanged in concentrated sulphuric acid, and oxidizes readily in moist air, forming Prussian blue . Prussian blue, Fe7(NC)is or Fe4[Fe(NC)s]s, ferric ferrocyanide, was discovered in 1710 by a See also:

• GERMAN
• GERMAN, DUTCH AND SCANDINAVIAN

German manufacturer named Diesbach, who obtained it by the action of fused alkali and iron salts on nitrogenous organic See also:

• MATTER

matter (e.g. See also:

• BLOOD

blood) . It is now prepared from the calcium ferrocyanide formed in gas purifiers (see above) by decomposition with ferrous sulphate . J .

Bueb (See also:

• CONGRESS (Lat. congressus, coming together, from congredi; cum, with, and gradus, step)

Congress of German Gas See also:

• INDUSTRIES

Industries, 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 1900) brings gas (free from See also:

• TAR

tar) into intimate contact with a saturated solution of ferrous sulphate, when a cyanogen mud " is obtained . This is heated to boiling, and the residue after filtration contains about 30% of Prussian blue . On the small See also:

• SCALE
• SCALE (1) A

scale it may be prepared by adding an acid solution of a ferrous salt to a solution of potassium ferrocyanide . The See also:

• GREY, CHARLES GREY, 2ND EARL (1764-1845)
• GREY, HENRY GREY, 3RD EARL (1802-1894)
• GREY, LADY JANE (1537-1554)
• GREY, SIR EDWARD
• GREY, SIR GEORGE (1812–1898)

grey precipitate first formed is allowed to stand for some See also:

• HOURS, CANONICAL

hours, well washed, and then oxidised by a warm solution of ferric chloride: 6K2Fe[Fe(NC)6] + 30 = Fe7(NC)1a + 3K4Fe(NC)s + Fe2O3• It is a dark blue See also:

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

powder with a marked coppery lustre . It is insoluble in water and is not decomposed by acids . Soluble Prussian blue, K2Fe2[Fe(NC)6]2, potassium ferric ferrocyanide, is formed when a solution of potassium ferrocyanide is added to an insufficiency of a solution of a ferric salt (I), or when potassium ferricyanide is added to a ferrous salt (2) : (1) 2K4Fe(NC)6 + 2FeCI3 = 6KCI + K2Fe2[Fe(NC)6]2 (2) 2K1Fe(NC)6 + 2FeC12 = 4KCI + K2Fe2[Fe(NC)612 . It is soluble in water, but is insoluble in salt solutions . Potassium ferricyanide, K3Fe(NC)6, red prussiate of potash, is obtained by oxidizing potassium ferrocyanide with See also:

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

chlorine, See also:

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

bromine, &c., 2K4Fe(NC)s + Cl2 = 2K3Fe(NC)6 + 2KC1 . G . Kassner (Chem . Zeit., 1889, 13, p . 1701; 17, p .

1712) adds calcium plumbate to a solution of potassium ferrocyanide and passes carbon dioxide through the mixture: 2K4Fe(NC)6 +Ca2PbO4+4CO2 =2K1Fe(NC)6+ K2CO3+PbCO3+2CaCO3• The mixture of calcium and lead carbonates is filtered off and roasted at a low red heat in order to regenerate the calcium plumbate . It crystallizes in dark red See also:

• MONOCLINIC

monoclinic prisms which are readily soluble in water . The solution decomposes on standing, and in the presence of an alkali acts as an oxidizing agent: 2K3Fe(NC)6+2KHO =2K4Fe(NC)6+H2O+0 . With silver nitrate it gives an See also:

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

orange red precipitate of silver ferricyanide, Ag3Fe(NC)6 . With a pure ferric salt it only gives 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 coloration . It can be estimated quantitatively by mixing a dilute solution with potassium iodide and hydrochloric acid in excess, adding excess of zinc sulphate, neutralizing the excess of free acid with sodium bicarbonate, and determining the amount of free See also:

• IODINE (symbol I, atomic weight '26.92)

iodine by a See also:

• STANDARD
• STANDARD, BATTLE OF THE

standard solution of sodium thiosulphate . The zinc sulphate is added in order to remove the ferrocyanide formed as an insoluble zinc salt: 2K2Fe(NC)6+2KI=2K4Fe(NC)6+I2 . As an alternative method it may be decomposed by hydrogen peroxide in alkaline solution and the amount of evolved oxygen measured: 2K2Fe(NC)s + 2KHO + H2O2 = 2K4Fe(NC)6 + 2H2O + 02 . Turnbull's blue, Fes(NC)12 or Fe3[Fe(NC)612, ferrous ferricyanide, is best obtained by adding a hot solution of potassium ferricyanide to a ferrous salt, and allowing the mixture to stand some 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 in the presence of an iron salt: 2K3Fe(NC)s+3FeSO4 = Fe3[Fe(NC)e]2+ 3K2SO4 . It is insoluble in dilute acids . Hydroferricyanic acid, H3Fe(NC)6, obtained by adding concentrated hydrochloric acid to 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 saturated solution of potassium ferricyanide, crystallizes in brown needles, and is easily decomposed . Nitroprussides.—The nitroprussides are salts of the type M2Fe(NC)6•NO .

The free acid forms dark red deliquescent crystals and is obtained by decomposing the silver salt with. hydrochloric acid, or the barium salt with dilute sulphuric acid . Sodium nitroprusside, Na2Fe(NC)sNO2H2O, is the commonest salt . It is prepared by oxidizing potassium ferrocyanide with a diluted nitric acid . The solution is evaporated, separated from potassium nitrate, the free acid neutralized with soda, and the solution concentrated . It crystallizes in dark red prisms which are readily soluble in water; it is a valuable reagent for the detection of sulphur, this See also:

• ELEMENT (Lat. elementum)

element when in the form of an alkaline sulphide giving a characteristic See also:

• PURPLE

purple blue coloration with the nitroprusside . The potassium salt may be prepared by adding potassium cyanide to ferrous sulphate solution, the brown precipitate so formed being then heated with potassium nitrite: 5 KNC + 2 FeSO4 = 2 K2SO4 + KFe2(NC)5, 2 KFe2(NC)s + 2 See also:

• KNO2

KNO2 = 2 FeO + 2 K2Fe(NC)5•NO . Other complex cyanides are known which may be regarded as derived from the acids H2X(CN)4, X= Ni, Pd, Pt; H4X(CN)6, X= Fe, Co, Ru; H3X(CN)6, X=Fe, Co, Rh; and H2R(CN)6 (see Abegg, Anorganischen Chemie) . Organic Cyanides or Nitriles.—Hydrocyanic acid forms two See also:

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

series of derivatives by the See also:

• EXCHANGE

exchange of its hydrogen See also:

• ATOM (Gr. &rows, indivisible, from a- privative, and TE,aPfw, to cut)

atom for alkyl or aryl See also:

• GROUPS
• GROUPS, THEORY

groups; namely the nitriles, of type R•CN, and the isonitriles, of type R.NC . The latter compounds may be Nitriles.—These substances were first isolated in 1834 by J . See also:

• PELOUZE, THEOPHILE JULES (1807-1867)

Pelouze (Ann., 1834, 10, p . 249) . They may be prepared by heating the alkyl iodides with potassium cyanide ; by heating sulphuric acid See also:

• ESTERS

esters with potassium cyanide; by distilling the acid-amides with See also:

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

phosphorus pentoxide; and by distilling See also:

• AMINES

amines (containing more than five atoms of carbon) with bromine and potash (A .

W . See also:

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

Hofmann), for example C7H11CH2NH2— C7H15CH2NBr2-jC7H36CN . In addition to these methods, the nitriles of the aromatic series may be prepared by distilling the aromatic acids with potassium sulphocyanide: C6H5CO2H + KCNS = HCNS + C8H6CO2K, C6H5CO2H + HCNS = C6H5CN + H2S + See also:

• CO2

CO2; from the See also:

• PRIMARY

primary aromatic amines by converting them into diazonium salts, which are then decomposed by boiling with potassium cyanide and See also:

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

copper sulphate; by fusing the potassium salts of the sulphonic acids with potassium cyanide; by leading cyanogen gas into a boiling hydro-carbon in the presence of See also:

• ALUMINIUM (symbol Al; atomic weight 27.0)

aluminium chloride (A . Desgrex, See also:

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

Bull. sec. chim., 1895, (3) 13, p . 735) ; and from the syn-aldoximes by the action of acetyl chloride or acetic anhydride . They are mostly colourless liquids which See also:

• BOIL

boil without decomposition, or solids of low melting point . The See also:

• LOWER

lower members of the series are somewhat soluble in water . They behave in most respects as unsaturated compounds; they combine with hydrogen to form amines; with water to form acidamides; with sulphuretted hydrogen to form thio-amides; with See also:

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

alcohols, in the presence of acids, to form imido-See also:

• ETHERS

ethers R•C(:NH)•ORI; with ammonia and primary amines to form See also:

• AMIDINES

amidines R.C(:NH).See also:

• NH2

NH2; and with See also:

• HYDROXYLAMINE, NH2OH

hydroxylamine to form amidoximes, R•C(:NOH)•NH2 . When heated with sodium they frequently polymerize . Heated with acids or alkalis theyy hydrolyse to acids: See also:

• RCN

RCN + HCI +2H2O = R•COOH +NH4C1 . This reaction shows that the alkyl or aryl See also:

• GROUP

group is attached to the carbon atom in the nitrile . Acetonitrile boils at 81.6° C., and is readily miscible with water .

Propionitrile boils at 97° C.; it is somewhat easily soluble in water, but is thrown out of solution by calcium chloride . It was obtained by E . See also:

• FRANKLAND, SIR EDWARD (1825-1899)

Frankland C . C . See also:

• GRAHAM, SIR GERALD (1831–1899)
• GRAHAM, SIR JAMES ROBERT GEORGE
• GRAHAM, SYLVESTER (1794-1851)
• GRAHAM, THOMAS (1805-1869)

Graham (Journ . Chem . Soc., 1880, 37, p . 740) by the action of cyanogen gas on zinc See also:

• ETHYL

ethyl . Allyl cyanide boils at 119° C . Benzonitrile boils at 190.6° C . When solidified it melts at—17° C . It is easily soluble in alcohol and ether .

The Isonitriles (isocyanides or carbylamines) were first prepared in 1866 by A . See also:

• GAUTIER
• GAUTIER, EMILE THEODORE LEON (1832-1897)
• GAUTIER, THEOPHILE (1811-1872)

Gautier (Ann., 1869, 151, p . 239) by the action of alkyl iodides on silver cyanide, and the distillation of the resulting See also:

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

compound with potassium cyanide in concentrated aqueous solution : RI-->R•Ag(NC)2-->R•NC+KAg(NC)2 . They may also be obtained by distilling a primary amine with alcoholic potash and chloroform: R•NH2 + CHC13 + 3KHO=3KCI + 3H2O + R.NC (A . W . Hofmann, Ann., 1868, 146, p . 107) . They are colourless liquids, readily soluble in alcohol and in ether, but insoluble in water . They possess an exceedingly unpleasant smell and are poisonous . They boil at temperatures somewhat lower than those of the corresponding nitriles; and ,are stable towards alkalis, but in the presence of mineral acids they readily hydrolyse, forming primary amines and formic acid: RNC+2H2O=RNH2+H2CO2• This reaction shows that the alkyl or aryl group is linked to the nitrogen atom . The carbon atom in the isonitriles is assumed by J . U .