See also:

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

ACID (from the See also:

• LAT

Lat. See also:

• ROOT (late O.E. rot, adopted from Scand., cf. Norw. and Swed. rot, Dan. rod; the true O.E. word was wyrt, plant, represented in Ger. Wurz or Wurzel; the ultimate root is the same in both words, and is seen in Lat. radix)
• ROOT, ELIHU (1845– )

root ac-, 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; acere, to be sour)  , the name loosely applied to any sour substance; in See also:

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

chemistry it has a more precise meaning,denoting a substance containing See also:

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

hydrogen which may be replaced by metals with the formation of salts . An See also:

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

acid may therefore be regarded as a 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 of hydrogen . Of the See also:

• GENERAL
• GENERAL (Lat. generalis, of or relating to a genus, kind or class)

general characters of acids we may here See also:

• NOTICE

notice that they dissolve alkaline substances, certain metals, &c., neutralize alkalies and redden many See also:

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

blue and See also:

• VIOLET

violet See also:

• VEGETABLE

vegetable' colouring matters . The ancients probably possessed little knowledge indeed of acids . See also:

• VINEGAR

Vinegar (or impure acetic acid), which is produced when See also:

• WINE (Lat. vinum, Gr. oivos)

wine is allowed to stand, was known to both the Greeks and See also:

• ROMANS
• ROMANS, EPISTLE TO THE

Romans, who considered it to be. typical of acid substances; this is philologically illustrated by the words 14&s, acidus, sour, and g os, acetus, vinegar . Other acids became known during the alchemistic See also:

• PERIOD
• PERIOD (Gr. irepioSos, a going or way round, circuit, aepi, round, and &Sis, way, road)

period; and the first See also:

• ATTEMPT (Lat. adtemptare, attentare, to try)

attempt at a generalized conception of these substances was made by See also:

• PARACELSUS (c. 1490-1541)

Paracelsus, who supposed them to contain a principle which conferred the properties of sourness and solubility . Somewhat similar views were promoted by See also:

• BECHER, JOHANN JOACHIM (1635-1682)

Becher, who named the principle acidum primogenium, and held that it was composed of the Paracelsian elements " 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" and "See also:

• WATER

water." At about the same 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 See also:

• BOYLE
• BOYLE, JOHN J
• BOYLE, ROBERT (1627-1691)

Boyle investigated several acids; he established their general reddening of 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, their solvent See also:

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

power of metals and basic substances, and the See also:

• PRODUCTION (Lat. productionem, from producere, to pro-duce)

production of neutral bodies, or salts, with alkalies . Theoretical conceptions were revived by See also:

• STAHL, FRIEDRICH JULIUS (1802-1861)
• STAHL, GEORG ERNST (1660-1734)

Stahl, who held that acids were the fundamentals of all salts, and the erroneous See also:

• IDEA (Gr. Ibia, connected with i&eiv, to see; cf. Lat. species from specere, to look at)

idea that sulphuric acid was the principle of all acids . The phlogistic theory of the processes of calcination and com=bustion necessitated the view that many acids, such as those produced by See also:

• COMBUSTION (from the Lat. comburere, to burn up)

combustion, e.g. sulphurous, phosphoric, carbonic, &c., should be regarded as elementary substances . This principle more or less prevailed until it was overthrown by See also:

• LAVOISIER, ANTOINE LAURENT (1743-1794)

Lavoisier's See also:

• DOCTRINE

doctrine that See also:

• OXYGEN (symbol 0, atomic weight 16)

oxygen was the acid-producing See also:

• ELEMENT (Lat. elementum)

element; Lavoisier being led to this conclusion by the almost general observation that acids were produced when non-metallic elements were burnt . The existence of acids not containing oxygen was, in itself, sufficient to overthrow this idea, but, although Berthollet had shown, in 1789, that sulphuretted hydrogen (or hydro-sulphuric acid) contained no oxygen, Lavoisier's theory held its own until the researches of See also:

• DAVY, SIR HUMPHRY

Davy, See also:

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

Gay-Lussac and See also:

• THENARD, LOUIS JACQUES (1777-1857)

Thenard on hydrochloric acid and See also:

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

chlorine, and of Gay-Lussac on hydro-cyanic acid, established beyond all cavil that oxygen was not essential to acidic properties . In the Lavoisierian nomenclature acids were regarded as binary oxygenated compounds, the associated water being relegated to the position of a See also:

• MERE
• MERE, ADALBERT (1838-1909)

mere solvent .

Somewhat similar views were held by See also:

• BERZELIUS, JONS JAKOB (1779-1848)

Berzelius, when developing his dualistic conception of the See also:

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

composition of substances . In later years Berzelius renounced the " oxygen acid " theory, but not before Davy, and, almost simultaneously, See also:

• DULONG, PIERRE LOUIS (1785—1838)

Dulong, had submitted that hydrogen and not oxygen was the acidifying principle . Opposition to the " hydrogen-acid " theory centred mainly about the hypothetical radicals which it postulated; moreover, the electrochemical theory of Berzelius exerted a stultifying See also:

• INFLUENCE (Late Lat. influentia, from influere, to flow in)

influence on the correct views of Davy and Dulong . In Berzelius' See also:

• SYSTEM

system + - See also:

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

potassium sulphate is to be regarded as See also:

• K20

K20.SO3; See also:

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

electrolysis should simply effect the disruption of the See also:

• POSITIVE (or PORTABLE) ORGAN

positive and negative components, potash passing with the current, and sulphuric acid against the current . Experiment showed, however, that instead of only potash appearing at the negative electrode, hydrogen is also liberated; this is inexplicable by Berzelius's theory, but readily explained by the " hydrogen-acid " theory . By this theory potassium is liberated at the negative electrode and combines immediately with water to See also:

• FORM (Lat. forma)

form potash and hydrogen . Further and stronger support was given when J . See also:

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

Liebig promoted his doctrine of polybasic acids . See also:

• DALTON
• DALTON, JOHN (1766-1844)

Dalton's idea that elements preferentially combined in equiatomic proportions had as an immediate inference that metallic oxides contained one See also:

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

atom of the 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 to one atom of oxygen, and a See also:

• SIMPLE

simple expansion of this conception was that one atom of See also:

• OXIDE

oxide combined with one atom of acid to form one atom of a neutral salt . This view, which was specially supported by Gay-Lussac and See also:

• LEOPOLD (M.H. Ger. Liupolt; O.H. Ger. Liupald, from hut, Mod. Ger. Leute, " people," and paid, " bold," i.e. " bold for the people ")

Leopold See also:

• GMELIN

Gmelin and accepted by Berzelius, necessitated that all acids were monobasic . The untenability of this theory was proved by See also:

• THOMAS
• THOMAS (c. 1654-1720)
• THOMAS (d. 110o)
• THOMAS, ARTHUR GORING (1850-1892)
• THOMAS, CHARLES LOUIS AMBROISE (1811-1896)
• THOMAS, GEORGE (c. 1756-1802)
• THOMAS, GEORGE HENRY (1816-187o)
• THOMAS, ISAIAH (1749-1831)
• THOMAS, PIERRE (1634-1698)
• THOMAS, SIDNEY GILCHRIST (1850-1885)
• THOMAS, ST
• THOMAS, THEODORE (1835-1905)
• THOMAS, WILLIAM (d. 1554)

Thomas See also:

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

Graham's investigation of the phosphoric acids; for he then showed that the ortho- (See also:

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

ordinary), pyro- and See also:

• META

meta-phosphoric acids contained respectively 3, 2 and r molecules of " basic water " (which were replaceable by metallic oxides) and one See also:

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

molecule of phosphoric oxide, P2 05 . Graham's See also:

• WORK

work was See also:

• DEVELOPED

developed by Liebig, who called into service many organic acids—citric, tartaric, cyanuric, comenic and meconic—and showed that these resembled phosphoric acid; and he established as the criterion of polybasicity the existence of See also:

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

compound salts with different metallic oxides .

In formulating these facts Liebig at first retained the dualistic conception of the structure of acids; but he shortly afterwards perceived that ;this view lacked generality since the halogen acids,' which contained no oxygen but yet formed salts exactly similar in properties to those containing oxygen, could not be so regarded . Th': and other reasons led to his rejection of the dualistic hypo-thesis and the See also:

• ADOPTION (Lat. adoptio, for adoptalio, from adoptare, to choose for oneself)

adoption, on the ground of See also:

• PROBABILITY (Lat. probabilis, probable or credible)

probability, and much more from convenience, of the tenet that " acids are particular compounds of hydrogen, in which the latter can be re-placed by metals "; while, on the constitution of salts, he held that " neutral salts are those compounds of the -same class in which the hydrogen is replaced by its See also:

• EQUIVALENT

equivalent in metal . The substances which we at See also:

• PRESENT

present See also:

• TERM

term anhydrous acids (acid oxides) only become, for the most See also:

• PART

part, capable of forming salts with metallic oxides after the addition of water, or they are compounds which decompose these oxides at somewhat high temperatures." The hydrogen theory and the doctrine of polybasicity as enunciated by Liebig is the fundamental characteristic of the See also:

• MODERN

modern theory . A polybasic acid contains more than one atom of hydrogen which is replaceable by metals; moreover, in such an acid the replacement may be entire with the formation of normal salts, partial with the formation of acid salts, or by two or more different metals with the formation of compound salts (see SALTS) . These facts may be illustrated with the aid of orthophosphoric. acid, which is tribasic: Acid . Normal salt . Acid salts . H3PO4• Ag3PO4 . Na2HPO4; NaH2PO4 . Phosphoric See also:

• SILVER

Silver phosphate . Acid See also:

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

sodium acid. See also:

• PHOSPHATES

phosphates . Compound salts .

Mg(NH4)PO4; Na(NH4)HPO4 . See also:

• MAGNESIUM [symbol Mg, atomic weight 24.32 (0 = 16)]

Magnesium ammonium Microcosmic phosphate; salt . Reference should be made to the articles CHEMICAL See also:

• ACTION

ACTION, See also:

• THERMOCHEMISTRY

THERMOCHEMISTRY and SOLUTIONS, for the theory of the strength or avidity of acids . Organic Acids.—Organic acids are characterized by the presence of the monovalent See also:

• GROUP

group — CO.OH, termed the carboxyl group, in which the hydrogen atom is replaceable by metals with the formation of salts, and by alkyl radicals with the formation of See also:

• ESTERS

esters . The basicity of an organic acid, as above defined, is determined by the number of carboxyl See also:

• GROUPS
• GROUPS, THEORY

groups present . Oxy-acids are carboxylic acids which also contain a hydroxyl group; similarly we may have aldehyde-acids, ketone-acids, &e Since the more important acids are treated under their own headings, or under substances closely allied to them, we shall here confine ourselves to general relations . See also:

• CLASSIFICATION (Lat. classis, a class, probably from the root cal-, cla-, as in Gr. icaMce, clamor)

Classification.—It is convenient to distinguish between aliphatic and aromatic acids; the first named being derived from open-See also:

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

chain See also:

• HYDROCARBONS

hydrocarbons, the second from ringed See also:

• HYDROCARBON

hydrocarbon nuclei . Aliphatic monobasic acids are further divided according to the nature of the See also:

• PARENT, SIMON NAPOLEON (1855– )

parent hydrocarbon . Methane and its homologues give origin to the "See also:

• PARAFFIN

paraffin" or " fatty See also:

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

series" of the general See also:

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

formula C, H2,H1COOH, See also:

• ETHYLENE, or ETHENE, C2H4

ethylene gives origin to the acrylic acid series., C,,H2, -1COOH, and soon . Dibasic acids of the paraffin series of hydrocarbons have the general formula C„H2(COOH)2'; malonic and succinic acids are important members . The See also:

• ISOMERISM

isomerism which occurs as soon as the molecule contains a few See also:

• CARBON (symbol C, atomic weight 12)

carbon atoms renders any classification based on empirical molecular formulae somewhat ineffective; on the other See also:

• HAND
• HAND (a word common to Teutonic languages; cf. Ger. Hand, Goth. handus)
• HAND, FERDINAND GOTTHELF (1786-185r)

hand, a See also:

• SCHEME (Lat. schema, Gr. oxfjya, figure, form, from the root axe, seen in exeiv, to have, hold, to be of such shape, form, &c.)

scheme based on molecular structure would involve more detail than it is here possible to give . For further See also:

• INFORMATION (from Lat. informare, to give shape or form to, to represent, describe)

information, the reader is referred to any See also:

• STANDARD
• STANDARD, BATTLE OF THE

standard work on organic chemistry .

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 acids present in fats and See also:

• OILS (adopted from the Fr. oile, mod. huile, Lat. oleum, olive oil)

oils is given in the See also:

• ARTICLE (from Lat. articulus, a joint)

article OILS . Syntheses of Organic . Acids.—The simplest syntheses are undoubtedly those in which a carboxyl group is obtained directly from the oxides of carbon, carbon dioxide and carbon monoxide . The simplest of all include: (I) the See also:

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

synthesis of sodium oxalate by passing carbon dioxide over metallic sodium heated to 3500—360 ; (2) the synthesis of potassium formate from moist carbon dioxide and potassium, potassium carbonate being obtained simultaneously; (3) the synthesis of potassium acetate and propionate from carbon dioxide and sodium methide and sodium ethide; (4) the synthesis of aromatic acids by the interaction of carbon dioxide, sodium and a See also:

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

bromine substitution derivative; and (5) the synthesis of aromatic oxy-acids by the interaction of carbon dioxide and sodium phenolates (see SALICYLIC ACID) . Carbon monoxide takes part in the syntheses of sodium formate from sodium See also:

• HYDRATE

hydrate, or soda See also:

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

lime (at 2000-2200), and of sodium acetate and propionate from sodium methylate and sodium ethylate at 16o°-2oo° . Other reactions which introduce carboxyl groups into aromatic groups are: the action of carbonyl chloride on aromatic hydrocarbons in the presence of See also:

• ALUMINIUM (symbol Al; atomic weight 27.0)

aluminium chloride, acid-chlorides being formed which are readily decomposed by water to give the acid; the action of See also:

• UREA, or CARBAMIDE, CO(NH2)2

urea chloride Cl•CO•See also:

• NH2

NH2, cyanuric acid (See also:

• CONH

CONH)3, nascent cyanic acid, or carbanile on hydrocarbons in the presence of aluminium chloride, acid-amides being obtained which are readily decomposed to give the acid . An important See also:

• NUCLEUS (Lat. for the kernal of a nut, nux, the stone of fruit)

nucleus-synthetic reaction is the saponification of nitriles, which may be obtained by the interaction of potassium See also:

• CYANIDE

cyanide with a halogen substitution derivative or a sulphonic acid . Acids frequently result as oxidation products, being almost invariably formed in all cases of energetic oxidation . There are certain reactions, however, in which oxidation can be success-fully applied to the synthesis of acids . Thus See also:

• PRIMARY

primary See also:

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

alcohols and See also:

• ALDEHYDES

aldehydes, both of the aliphatic and aromatic series, readily yield on oxidation acids containing the same number of carbon atoms . These reactions may be shown thus: R•See also:

• CH2OH

CH2OH - R•CHO -> R•CO.OH . In the See also:

• CASE
• CASE, JOHN (d. 1600)

case of aromatic aldehydes, acids are also obtained by means of " See also:

• CANNIZZARO, STANISLAO (1826-1910)

Cannizzaro's reaction " (see See also:

• BENZALDEHYDE (oil of bitter almonds), C6H5CHO

BENZALDEHYDE) .

An important oxidation synthesis of aromatic acids is from hydro-carbons with aliphatic See also:

• SIDE
• SIDE (mod. Eski Adalia)

side chains; thus See also:

• TOLUENE, or METHYLBENZENE

toluene, or methyl-See also:

• BENZENE, C6H6

benzene, yields benzoic acid, the xylenes, or dimethyl-benzene, yield methyl-benzoic acids and See also:

• PHTHALIC

phthalic acids . See also:

• KETONES

Ketones, secondary alcohols and See also:

• TERTIARY

tertiary alcohols yield a mixture of acids on oxidation . We may also notice the disruption of unsaturated acids at the 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 linkage into a mixture of two acids, when fused with potash . In the preceding instances the carboxyl group has been synthesized or introduced into a molecule; we have now to consider syntheses from substances already containing carboxyl groups . Of foremost importance are the reactions termed the malonic acid and the aceto-acetic ester syntheses; these are discussed under their own headings . The electrosyntheses See also:

• CALL (from Anglo-Saxon ceallian, a common Teutonic word, cf. Dutch kallen, to talk or chatter)

call for mention here . It is apparent that metallic salts of organic acids would, in aqueous See also:

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

solution, be ionized, the positive See also:

• ION

ion being the metal, and the negative ion the acid See also:

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

residue . Esters, how-ever, are not ionized . It is therefore apparent that a mixed salt and ester, for example K02C•See also:

• CH2
• CH2(OH)

CH2•CH2•CO2C2H5i would give only two ions, viz. potassium and the See also:

• REST (O. Eng. rest, reste, bed, cognate with other Teutonic forms, e.g. Ger. Rast, Riiste, rest, and probably Gothic Rasta, league, i.e. resting or stopping place)

rest of the molecule . If a solution of potassium acetate be electrolysed the products are ethane, carbon dioxide, potash and hydrogen; in a similar manner, normal potassium succinate gives ethylene, carbon dioxide, potash and hydrogen; these reactions may be represented: See also:

• CH3

CH3•See also:

• CO2

CO2;K CH3 CO2 K' CH2•CO2K CH2 CO2 IC --> I + + I ;-ii + + CH3•CO21K CH3 CO2 K' CH2•CO21K CH2 CO2 K' By electrolysing a solution of potassium See also:

• ETHYL

ethyl succinate, K02C•(CH2)2CO2C2H5, the K02C• groups are split off and the two residues •(CH2)2CO2C2H5 combine to form the ester (CH2)4(CO2C2H5)2 . In the same way, by electrolysing a mixture of a metallic salt and an ester, other nuclei may be condensed; thus potassium acetate and potassium ethyl succinate yield CHa•CH2.CH2•CO2C2H5 . Reactions.—Organic acids yield metallic salts with bases, and ethereal salts or esters (q.v.), R•CO.OR', with alcohols .

See also:

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

Phosphorus chlorides give acid chlorides, R.CO.Cl, the hydroxyl group being replaced by chlorine, and acid anhydrides, (R.CO)20, a molecule of water being split off between two carboxyl groups . The ammonium salts when heated lose one molecule of water and are converted into acid-amides, R . CO•NH2, which by further dehydration yield nitriles, R• CN . The calciumsalts distilled with See also:

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

calcium formate yield aldehydes (q.v.); distilled with soda-lime, ketones (q.v.) result .