Rudolph August Witthaus.

Text-book of chemistry, inorganic and organic, with toxicology; for students of medicine, pharmacy, dentistry and biology online

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gallo-tannic acid. It is formed when bromo-protocatechuic acid is fused with,



360 TEXT-BOOK OF CHEMISTRY

caustic potash. It crystallizes in long, silky needles with lAq, odorless, acidu-
lous in taste, sparingly soluble in cold water, very soluble in hot water and
in alcohol. Its solutions are acid. When heated to 210-215 it yields CO 2 and
pyro-gallol. Its solutions reduce the salts of silver and of gold; they do not
precipitate gelatin nor the salts of the alkaloids, as does tannin; and they
give a blue-black precipitate with FeCl 3 .

Tannins Tannic Acid are substances of vegetable origin, principally de-
rived from leaves, barks and seeds. They are amorphous, soluble in water,
astringent, capable of precipitating albumin, of forming imputrescible com-
pounds with the gelatinoids (leather), and give green or blue colors with the
ferric salts.

Pure tannic acid has been obtained by removal of water from gallic acid:
2C 7 H 6 O 5 =C 14 H 10 O 9 -f-H s! O; it is, therefore, digallic acid. It exists in gall-nuts,
excrescences produced upon oak trees by the punctures of certain insects (gallo-
tannic acid ) . It is colorless, amorphous, odorless, very soluble in water, less so
in alcohol, almost insoluble in ether. It forms a dark-blue liquid (ink) with
solutions of ferric salts or, after exposure to air, with ferrous salts.

Caffetannic Acid, C 30 H 1B O, 6 , exists in saline combination in coffee and
Paraguay tea. It colors the ferric salts green, precipitates the salts of quinine
and cinchonine, but not tartar emetic or gelatin, as tannic acid does. It yields
caffeic acid, or 3-4 dioxycinnamic acid, C 9 H 8 O 4 , on decomposition. Cachou-
tannic acid obtained from catechu, is soluble in water, alcohol and ether. It pre-
cipitates gelatin, but not tartar emetic, and colors ferric salts grayish-green.
Morintannic acid, or maclurine, C 13 Hi O 6 , is a yellow, crystalline substance, ob-
tained from fustic. It is more soluble in alcohol than in water. Its solutions
precipitate greenish-black with ferric salts, yellow with lead acetate, brown
with tartar emetic and yellowish-brown with cupric sulphate. Quercitannic
acid, C ltt Hi 6 O, , is the tannin of oak bark. It is a red powder, sparingly soluble
in water, which forms a violet-red precipitate with ferric salts. Quinotannic
acid exists in cinchona barks, in combination with the alkaloids. It is light
yellow, soluble in water, alcohol and ether, astringent, but not bitter in taste.
It is colored green by ferric salts. Dilute H 2 S0 4 decomposes it with formation
of quina red, an amorphous substance, which yields protocatechuic and acetic
acids on further decomposition.

PHENYLIC ETHERS GLUCOSIDES.

The oxides of the aromatic series, corresponding to the aliphatic ethers,
and containing two cyclic hydrocarbon groups united by an oxygen atom,
properly belong among the dibenzenic compounds but are more conveniently
considered here.

Phenyl Ether Diphenyl Oxide (C a H 5 ) 2 O is formed by heating phenol
with aluminium chloride, or with zinc chloride:

2C 8 H 8 .OH=C 6 H 5 .O.C 6 H 5 +H J f

and by other more circuitous methods. It crystallizes in long needles,
having the odor of geranium, soluble in alcohol and in ether. Corresponding to
it are a number of derivatives, formed by substitution of various univalents for
the remaining phenol hydrogen.

The mixed oxides, containing a phenyl and an alkyl group, are the phenyl
ethers or phenol esters, derived from phenol. They are formed by heating
metallic phenates with alkyl halides:

C fl H 5 .O.K+CH 8 I=C 6 H 5 .O.CH,-fKI

as the aliphatic ethers are produced from metallic alcoholates and alkyl halides.
Methyl-phenyl Ether Anisol C 6 H 5 .O.CH 8 is a colorless, thin liquid,



GLUCOSIDES 361

boils at 152 without decomposition. Sulphuric acid dissolves it, with forma-
tion of irfethyl-phenol sulphonic acid.

Ethyl-phenyl Ether Phenetol C 6 H 5 .O.C 2 H 5 is a colorless liquid, having
an aromatic odor. It boils at 172.

GLUCOSIDES.

The name "glucoside" was first applied to certain natural prod-
ucts, some of which are the active constituents of medicinal plants,
which, on decomposition by dilute mineral acids, yield glucose and
some other substance. Subsequently, it was found that the sugars
derived from some of these substance", differ from glucose; some are
pentoses, others hexoses; some monosaccharides, others disaccharides ;
some aldoses, others ketoses. On the other hand, the second product
of decomposition has been of the most varied character, phenols,
alphenols, alcohols, oxyphenols, monobenzenic or dibenzenic, but, in
all those natural glucosides which have been investigated, always a
cyclic compound, containing a phenolic or an alcoholic group. The
glucosides have usually been regarded as esters of glucose, etc., since
the alcoholic character of the sugars has been recognized, but, as
the union of the sugar and benzenic components is through an oxygen
atom, and not by replacement of the hydrogen of a carboxyl, they
are more properly regarded as ethers, formed by union of an aldose
or ketose remainder with one of a phenolic or alcoholic benzenic
compound, with elimination of H 2 0. The constitution of the gluco-
sides cannot, however, be considered as established, as no natural
glucoside has been obtained synthetically, although the products of
decomposition of some are comparatively simple compounds. It
is to be supposed that the union takes place through the aldehyde
group, as the glucosides do not reduce Fehling's solution and do
not form osazones. They probably contain some such grouping as:

/ON

CH 2 OH.(CHOH) 3 .CH CH.O.B, in which B represents the ben-
zenic component.

The glucosides are decomposed (hydrolyzed) by heating with
dilute acids, or, at very slightly elevated temperatures, by certain
enzymes, such as emulsin, which exists in almonds, myrosin, in mus-
tard seeds, the invertin of malt, and salivary and intestinal enzymes.
They are very slowly hydrolyzed by heating with water under, pres-
sure, if at all ; and only a few of them are decomposed by alkalies.

The glucosides yielding pentoses on hydrolysis are more properly
designated pentosides.

Phenyl Glucosides Glucosyl phenate CgH^Os.O.CeHg is the
simplest of the glucosides, and is an artificial product, formed by
mixing alcoholic solutions of acetochlorhydrose and potassium
phenate :

CHO. ( CH.C0 2 .CH 3 ) 4 .CH 2 C1+C 6 H 5 .O.K+4H 2 0=CHO. ( CHOH) 4 .-
CH 2 .O.C 6 H 5 +KC1+4CH 3 .COOH



362 TEXT-BOOK OF CHEMISTRY

It forms soluble, crystalline needles, fusible at 172, and is de-
composed by emulsin into glucose and phenol.

Among the more important of the natural glucosides are the fol-
lowing:

JEsculin Ci 5 H 18 B which exists in the rinds of horse-chestnuts. It forms
colorless crystals, sparingly soluble in water, the solutions having a brilliant
blue fluorescence, even when very dilute. It forms a yellow solution with
HNO 3 , which becomes deep blood-red on supersaturation with ammonia. It is
decomposed by dilute mineral acids, or by emulsin, into glucose and aesculetin,

/CH:CH
CoH.Oi, which is probably a dioxy-derivative of coumarin: C 6 H 2 (OH) 2

\0 CO

Amygdalin C 20 'H. 27 N0 11 exists in the bitter almond, in the ker-
nels of peach- and plum-pits, apple- and pear-seeds, and a great
variety of other plants. It crystallizes in colorless prisms with 3 Aq,
easily soluble in water, insoluble in ether, odorless, and bitter. It is
decomposed by dilute mineral acids, or by emulsin, into two mole-
cules of glucose and one each of benzoic aldehyde and hydrocyanic
acid:

C 20 H 27 N0 11 +2H 2 0=2C 6 H 7 0(OH) 5 +C 6 H 5 .CHO+CNH

By the action of alkalies, particularly by heating with Ba(OH) 2 ,
amygdalin yields amygdalic acid, C 20 H 28 13 , of which amygdalin ap-
pears to be the nitrile: C 6 H 7 0(OH) 4 .O.C 6 H 7 0(OH) 3 .O.CH(C X 6 H 5 )CN
and this, on splitting off of the sugar, first forms the nitrile of man-
delic acid: C 6 H 5 .CHOH.CN, the subsequent decomposition of which
into C 6 H 5 .CHO and HCN is evident. Amygdalin itself is non-poi-
sonous, but its ready decomposition, with formation of the extremely
poisonous hydrocyanic acid, is a prolific source of cyanic poisoning.

Coniferin C, fl H 22 O 8 is a glucoside occurring in the inner bark (cambium)
of coniferous plants, and in asparagus and the sugar-beet. It crystallizes in
silky, white needles, sparingly soluble in water, faintly bitter. With phenol
and concentrated hydrochloric acid it assumes an intense blue color (pine-shaving
reaction). It is decomposed by emulsin into glucose and coniferyl alcohol, which

is a hydroxyl-oxymethyl cinnamyl alcohol: CH 3 J^Q^C 6 H 3 .CH:CH.CH 2 OH. By

oxidation with chromic acid it forms glucovanillin, C a H n 5 .O.C 6 H 3 (OCH 3 )CHO,
which is decomposed by emulsin into glucose and vanillin: methylprotocatechuic
aldehyde. Glucovanillin, containing an aldehyde group, forms a crystalline com-
pound with phenylhydrazine, and an oxime. By further oxidation it forms
glucovanillic acid, and by reduction, the corresponding alcohol.

Daphnin, C 18 H 18 O B , occurs in the bark of Daphne mezereum, and other
species of Daphne. It crystallizes in colorless prisms, bitter and astringent,
sparingly soluble in water and in ether, soluble in alcohol. It is colored bluish
by ferric chloride. It is decomposed into glucose and daphnetin, C 9 H 8 O 4 , isonicric
with aesculetin (above). Daphnetin has been shown to be a dioxycoumarin,
having the hydroxyls in the positions 1, 2, by its synthesis by condensation of
pyrogallol and malic acid:

CH, ( OH ) 8 (i-iwj) +COOH.CH 2 .CHOH.COOH=H.COOH+2H 2 0+

/O(3> CO
C,H 2 (OH) 2 (i2>

\CH(*):CH



GLUCOSIDES 363

Digitalis Glucosides. The active substance of digitalis consists,
in part at least, of a glucoside, or glucosides, probably accompanied
by products of decomposition, but the chemistry of these compounds
requires further investigation. Digitonin, C 27 H 44 13 ( ?), is the most
abundant constituent of the ' ' amorphous digitalins, ' ' and has little or
no therapeutic value. It is an amorphous, white solid, very sol-
uble in water, which crystallizes from its alcoholic solutions. It is
decomposed by dilute hydrochloric acid into digitone'in, or digito-
genin, C 15 H 24 4 , glucose and galactose. Digitalin, (C 5 H 8 2 )n( ?),
separates in amorphous or nodular masses from its alcoholic solution.
On decomposition it yields digitaliresin, C 16 H 22 2 , glucose and digi-
talose, C 7 H 14 5 . It has the physiological action of digitalis upon the
heart, and is the principal constituent of "Homolle's digitalin."
Digitoxin, C 21 H 32 7 (?), crystallizes in fine needles, insoluble in
water, soluble in hot alcohol and in chloroform. It is the most
actively poisonous of the digitalis glucosides, and is the chief con-
stituent of "Nativelle's digitalin." Digitalin gives a color-reaction
which is not given by digitoxin : it forms a golden-yellow or brownish
solution with concentrated H 2 S0 4 , which becomes violet-red by the
action of bromine vapor.

Toxicology. The prominent symptoms of poisoning by digitalis are:
nausea, and occasionally vomiting; sometimes colic and diarrhea; after two or
three hours, marked diminution in the frequency of the pulse, which may fall to
40 or even 25; dyspnea, attended by a sense of oppression in the chest and
coldness of the extremities; headache, vertigo, and tendency to sleep; usually
attacks of synocope occur, provoked sometimes by the slightest movement of the
patient; death is generally by syncope, sometimes after several hours of coma
succeeded by convulsions.

The treatment: The patient must be kept strictly in the recumbent posi-
tion. The stomach should be washed out with infusion of tea by the stomach
tube. Stimulants should be given.

Indican C 26 H 31 N0 17 is a glucoside occurring in the indigo
plant. It is a yellow or light brown syrup, which cannot be dried
without decomposition, bitter and disagreeable in taste, acid in re-,
action, and soluble in water, alcohol and ether. It is very prone to
decomposition. Even slight heating decomposes it into leucine,
indicanin, C 20 H 23 N0 12 , and indiglucin, C 6 H 10 6 . A characteristic
decomposition is that by which it yields indigo-blue and indiglucin,
along with other products :

2C 20 H 31 N0 17 +4H 2 0=C 16 H 10 N 2 2 +6C 6 H 10 6

The substance found in the urine, and erroneously called "indi-
can," is not a glucoside, but is potassium indoxyl sulphate: K.C 8 H 6 -
N.S0 4 (see p. 417).

Myronic Acid, C, Hi 9 NS 2 10 , exists in the seeds of black mustard as its K
salt, which is hydrolyzed by myrosin into glucose, allyl isothiocyanate and
KHS0 4 .



364 TEXT-BOOK OF CHEMISTRY

Phloridzin, C 21 H ?4 O 10 , occurs in the root-bark of apple and other fruit trees.
When ingested it causes glycosuria. It is hydrolyzed by boiling with dilute
acids, or even with water, into a crystalline, dextrogyrous hexose, phlorose,
and phloretin, C ]5 H 14 O 5 , which is further decomposed by hot alkalies into phloro-
glucin and phloretic, or p-oxyhydratropic acid: CH 4 ( OH ) .C 2 H 4 .COOH.

Salicin C 13 H 18 7 occurs in willow bark. It is a white, crys-
talline substance, insoluble in ether, soluble in water and in alcohol,
very bitter in taste. Concentrated H 2 S0 4 colors it intensely red, the
color being discharged by addition of water. It is decomposed by
emulsin, by saliva, or by mineral acids into glucose and saligenin.
When taken into the economy it is converted into salicylic aldehyde
and acid, which are eliminated in the urine. Populin, a glucoside
from poplar bark, is benzoyl-salicin.

Santonin C 15 H 18 3 is the active glucoside of the Artemisia pauci-
flora. It is used as an anthelmintic.

Solanin C 42 H 87 N0 15 ( ?) is a glucoside having basic properties,
an alkaloid-glucoside, occurring in a variety of plants of the genus
Solanum. It crystallizes in white, silky needles, acrid and bitter in
taste, insoluble in water, sparingly soluble in alcohol and in ether. By
the action of hot dilute acids it is decomposed into glucose and a
basic substance, solanidin.



ANHYDRIDES AND ACID HALIDES.

The aromatic acidyls form oxides, or anhydrides, and haloid com-
pounds, corresponding to those of the aliphatic acidyls, and produced
by similar methods.

Benzoic Anhydride (C 6 H 5 .CO) 2 is formed from benzoyl chlor-
ide by several methods : as by a reaction between benzoyl chloride and
silver benzoate:

C 6 H 5 .CO.Cl+C 6 H 5 .COOAg=(C 6 H 5 .CO) 2 0+AgCl

It is a crystalline solid, f. p. 42, b. p. 360.

Phthalic Anhydride C 6 H 4 (CO) 2 :0 being formed from a dicar-
boxylic acid, is produced from a single molecule of the acid, with
elimination of H 2 0. It is formed by fusing phthalic acid. It sub-
limes in needles; f. p. 128; sparingly soluble in cold water, soluble
in hot water, with regeneration of the acid, very soluble in alcohol
and in ether. It combines with phenols to form phthaleins.

Salicylic Anhydride Salicylide C 6 H 4 /g^g\C 6 H 4 (probably)

is formed by the action of phosphorus oxychloride on salicylic acid,
It forms a crystalline compound with chloroform in which the latter
behaves as water of crystallization : (C 7 H 4 2 ) 4 .2CHC1 3 , which is
utilized to purify that anesthetic.

Benzoyl Chloride C e H 5 .CO.Cl was the first obtained of the



AROMATIC SULPHUR-DERIVATIVES SULPHONIC ACIDS 365

acidyl halides. It is formed by the action of hydrochloric acid upon
benzoic acid, in presence of phosphorus pentoxide:

C 6 H 5 .COOH+HC1=C 6 H 5 .CO.C1+H 2
Or by the action of chlorine upon benzoic aldehyde:

C 6 H 5 .CHO+C1 2 =HC1+C 6 H 5 .CO.C1

Or, along with acetyl chloride, by the action of chlorine upon
benzyl acetate:

CH 3 .COO(CH 2 .C 6 H 5 )+2C1 2 =:C 6 H 5 .CO.C1+CH 3 .CO.C1+2HC1

The two chlorides are separated by fractional distillation.
Benzoyl chloride is a colorless liquid; b. p. 198; having a pene-
trating odor. With silver (or mercuric) cyanide it forms benzoyl
cyanide :

C 6 H 5 .CO.Cl+AgCN=C 6 H 5 .CO.CN+AgCl

It acts readily upon the polyatomic alcohols and upon the hexoses,
when shaken with their solutions in presence of caustic soda. With
the hexoses pentabenzoyl compounds are formed, and crystallize out:
CHO.C 5 H 6 (OH) 5 +5C 6 H 5 .CO.C1=CHO.C 5 H 6 (O.CO.C 6 H 5 ) 5 +5HC1

This is a reaction utilized for the isolation of hexoses and poly-
atomic alcohols. A similar reaction, similarly utilized, occurs with
the diamines, in which insoluble, crystalline, dibenzoyl compounds
are formed :

C 2 H 4 (NH 2 ) 2 +2C 6 H 5 .CO.C1=C 2 H 4 (NH.CO.C 6 H 5 ) 2 +2HC1

AROMATIC SULPHUR-DERIVATIVES SULPHONIC ACIDS.

Many thio-aromatic compounds are known, as thiophenol, C 6 H 5 .-
SH, phenyl sulphide, (C 6 H 5 ) 2 S, and thio-benzoic acid, C 6 H 5 .COSH.
But the most important of the aromatic compounds containing sul-
phur are the

Sulphonic Acids (p. 286), monobasic acids containing the group
S0 3 H, formed by the union of the aromatic hydrocarbon, or deriva-
tive, with H 2 S0 4 with elimination of OH from the acid and H from
the aromatic compound, a process called "sulphonation": C 6 H 6 +H 2 -
S0 4 =C 6 H 5 .S0 3 H-|-H 2 0. The aromatic and polybenzenic sulphonic
acids are formed much more readily than the corresponding aliphatic
acids, and, being acid and soluble, are largely used as dyes. They
are usually produced by the action of fuming H 2 S0 4 upon the aro-
matic compound, with or without the aid of heat.

The sulphonic acids are not decomposed by boiling with alkaline
solutions, but their salts, when fused with caustic alkalies, yield
phenols :

C 6 H 5 .S0 3 K+KOH=C 6 H 5 .OH+K 2 S0 3

Distilled with potassium cyanide they yield nitriles :
C 6 H 5 .S0 3 K+KCN=C 6 H 5 .CN+K 2 S0 3



366 TEXT-BOOK OF CHEMISTRY

By the action of PC1 5 they are converted into their chlorides,
e.g., C 6 H 5 .S0 2 C1, which may be, in turn, converted into sulphinic
acids, sulphones, etc. They are easily soluble in water, and may be
separated from their solutions, as sodium salts, by the addition of
NaCl.

Benzene-monosulphonic Acid C 6 H 5 .S0 3 H is formed by dis-
solving benzene in weak fuming sulphuric acid at a slightly elevated
temperature, and diluting with H 2 0. It crystallizes in extremely
soluble, deliquescent plates with l l / 2 Aq. By the action of PC1 5 upon
benzene monosulphonates, benzene sulphochloride is produced:
C 6 H 5 .S0 3 K+PC1 5 =C 6 H 5 .S0 2 C1+KC1+POC1 3

This is an oily liquid, b. p. 246, which is a valuable reagent for
amines and amido compounds.

Three benzene-disulphonic acids C 6 H 4 (S0 3 H) 2 ortho-, meta-
and para-, are known, also one benzene-trisulphonic acid
C 6 H 3 (S0 3 H) 3 .

Three toluene-sulphonic acids C 6 H 4 (CH 3 ).S0 3 H ortho-, meta-
and para-, have been obtained. By the action of a mixture of ordi-
nary and fuming sulphuric acids upon toluene at a temperature not
exceeding 100, a mixture of the ortho- and para- acids is produced.
When this is treated with PC1 5 , it is converted into a mixture of para-
and ortho-toluene sulphonic chlorides C 6 H 4 .CH 3 .S0 2 C1. The
ortho-chloride, when acted on by dry ammonia and ammonium car-
bonate, is converted into ortho-toluene sulphamide CJEI^CHg.-
S0 2 NH 2 . This product, when oxidized by potassium permanganate,
is converted into benzoyl-sulphonic imide C fi H 4 .CO.S0 2 NH
benzosulphinidium, or benzosulphinide or saccharin of the U. S. P.
an odorless, crystalline powder, having great sweetening power,
its sweet taste being still detectable in a dilution of 1-50,000. Spar-
ingly soluble in water and in ether, readily in alcohol. Its solutions
are acid in reaction. When heated with Na 2 C0 3 it is carbonized and
gives off the odor of benzene. It is not attacked by H 2 S0 4 .

Another series of sulphonic derivatives is obtained from the
phenols. Among them is:

Ortho-phenol sulphonic Acid Sozolic acid Aseptol C 6 H 4 -
(OH) (1) (S0 3 H) (2) which is prepared by the action of cold concen-
trated H 2 S0 4 upon phenol. It is a reddish, syrupy liquid, soluble in
H 2 in all proportions, has a faint and not disagreeable odor. It
prevents fermentation and putrefaction, and is a non-poisonous, non-
irritant antiseptic. The salts of this and the corresponding para-
and meta-acids have been used as antiseptics and insecticides, under
the name of sulphocarbolates or phenol-sulphonates, e. g. Sodii
phenolsulphonas (U. S. P.).

Phenylsulphuric Acid Monophenyl Sulphate CO ^Q/ S0 2 iso-
meric with the phenol monosulphonic acids, and corresponding to



NITROGEN- CONTAINING DERIVATIVES OF BENZENE 367

the acid ethyl sulphuric ester, ethylsulphuric acid, is the acid phenyl
sulphuric ester which exists in its salts in the urine, and is the type
of numerous similar compounds, the " ester sulphates," which are
formed in the economy from substances containing a phenolic hy-
droxyl. The potassium salt of the acid is obtained by the action of
potassium pyrosulphate upon potassium phenate:

S 2 7 K 2 +C 6 H 5 .OK=C 6 H 5 .O.S0 3 K+S0 4 K 2
The free acid decomposes rapidly.

NITROGEN-CONTAINING DERIVATIVES OF BENZENE.

The nitrogen derivatives of benzene are very numerous, of great
variety of structure, and include among their number several sub-
stances of great industrial value.

They may be classified into five principal groups: (1) The nitro-
compounds, derived from other benzenic compounds by substitution
of N0 2 for H, and the nitroso-compounds, containing the nitroso
group, NO; (2) the hydroxylamine compounds, containing the
group N \H H ' an( * the * r n i troso derivatives; (3) the amido- and
imido-compounds, containing NH 2 and NH, the aromatic amines,
amides, and amido-acids, and their derivatives; (4) the azo- and
diazo-compounds and their numerous derivatives, containing the
grouping N=N ; (5) the hydrazines, containing the grouping
=N N=, and their nitroso derivatives.

NITRO- AND NITROSO-COMPOUNDS

Nitro-benzenes. These contain the nitro group directly attached
to the carbon of the benzene ring. They are produced by the action
of fuming HN0 3 , or a mixture of HN0 3 and H 2 S0 4 , upon the hydro-
carbons :

C 6 H 6 +HN0 3 =C 6 H 5 .N0 2 +H 2

They are yellow liquids, sparingly soluble in water. Their most
important property is their ready reduction, first to hydroxylamine
compounds :

C 6 H 5 .N0 2 +2H 2 =C 6 H 5 .NH.OH+H 2

and then to amicto-compounds :

C 6 H 5 .NH.OH+H 2 =C 6 H 5 .NH 2 +H 2

Mono-nitro-benzene Nitro-benzol Nitro-benzene Essence of
Mirbane C G H 5 .N0 2 is obtained by the moderated action of fuming
HN0 3 , or of a mixture of HN0 3 and H 2 S0 4 on benzene.

It is a yellow, sweet liquid, with an odor of bitter almonds; sp.
gr. 1.209 at 15; boils at 213; almost insoluble in water; very
soluble in alcohol and in ether. Concentrated H 2 S0 4 dissolves, and,
when boiling, decomposes it. Boiled with fuming HN0 3 it is con-



368



TEXT-BOOK OF CHEMISTRY



verted into dinitro-benzenes. It is converted into aniline by re-
ducing agents.

It has been used in perfumery as artificial essence of bitter al-
monds; but as inhalation of its vapor, even largely diluted with air,
causes headache, drowsiness, difficulty of respiration, cardiac irregu-
larity, loss of muscular power, convulsions, and coma, its use for that
purpose is to be condemned. Taken internally, it is an active poison.

Nitro-benzene may be distinguished from oil of bitter almonds
(benzoic aldehyde) by H 2 S0 4 , which does not color the former; and
by the action of acetic acid and iron filings, which convert nitro-
benzene into aniline, whose presence is detected by the reactions for
that substance (p. 371).

Dinitrobenzenes. The three dinitrobenzenes are produced by
boiling the mono-nitro compound with fuming HN0 3 . The meta-
compound predominates, and may be separated by fractional crystal-
lization from alcohol. It crystallizes in plates, fusible at 90, and
is used in the preparation of certain dyes, and of explosives, such
as roburite, sicherheit, etc. The gases resulting from such explo-
sives are poisonous.

Nitrotoluenes. C 6 H 4 .CH 3 .N0 2 The o- and p-compounds are pro-
duced together by nitration of toluene, and exist in the commercial
nitro-benzene. They may be separated by fractional distillation, the
o-compound boiling at 218, and the p- at 230. By reduction they
yield the corresponding toluidines, largely used in the color industry.

By the action of HN0 3 on nitrobenzene, meta-compounds are ob-
tained principally :



NO,



NO,




+ HNO, =




+H,0



NO 2



And by action of HN0 3 on toluene, we obtain a mixture of ortho-
and para-nitrotoluene :



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