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heating to 160 170, it melts with loss of water and is
converted into an amorphous red compound, C 2 , ( rI < , O l0 , which
may also be obtained by heating kino-red with dilute hydro-
chloric or sulphuric acids. On dry distillation, the larger



SINAPIN. 375



portion becomes carbonized, phenol, catechol and a small
amount of anisol or guaiacol being formed. 1

2205 Sinapin, C^H^NOg. Henry and Garot discovered in
the seeds of the white mustard, a crystalline compound, con-
taining both sulphur and nitrogen, to which they gave the
name of sulphosinapin, 2 and which was subsequently recognized
by Babo and Hirschbrunn as sinapin thiocyanate. 3 Robiquet
and Boutron Charlard, repeating the research of Henry and
Garot, obtained another substance, 4 which Will and Lauben-
heimer named sinalbin, and which is resolved into acid sinapin
sulphate, sinalbin mustard oil, and grape sugar, by the action of
myrosin in aqueous solution (Vol. III., Part II., p. 449).

Sinapin, which is generally classed among the alkaloids, is
extremely deliquescent, but forms stable salts.

Sinapin thiocyanate, C 16 H. 23 NO 5 .HSCN, is obtained from the
powdered seeds by first extracting them with ether and cold
alcohol, and then boiling up with 90 per cent, alcohol. A very
voluminous crystalline mass, which bears a strong resemblance
to quinine sulphate, separates out on cooling. It crystallizes
from a dilute, hot, aqueous solution in large, fascicular groups of
needles, which melt at I76, 5 and are only slightly soluble in cold
alcohol and water.

Add sinapin sulphate, C 16 H 23 NO 5 ,H 2 SO 4 + 2H 2 O, is obtained
by adding sulphuric acid to a concentrated, hot solution of the
thiocyanate ; it crystallizes in rectangular plates, has an acid
reaction and is readily soluble in water.

The normal sulphate may be prepared from the acid by
neutralizing with baryta water and evaporating the filtrate ;
it forms an extremely soluble crystalline mass. The nitrate
and hydrcchloride of sinapin can be prepared from it by means
of barium nitrate or chloride, and crystallizes in fine, very
soluble needles. The hydrochloride combines with mercuric
chloride to form the compound C^H^NO^HCl + HgCl. 2 , which
crystallizes from water in thin, lustrous prisms (Will and
Laubenheimer).

When the sulphuric acid is completely removed by baryta
water from a solution of the sulphate, a solution of free sinapin
is obtained which has a deep yellow colour, is alkaline to litmus,

Jic.r. Dcutsch. Chcm. Ges. xi. 1879.

I '.i !/<! ins, Jahrcsbcr. vi. 242 ; xii. 263.

Ann. C'hem. Pharm. Ixxxiv. 10.

Borzelins, JaJircsber. xii. 266.

Kemsen ami Coale, Amer. Clic-in. Journ. vi. 50.



376 AROMATIC COMPOUNDS.

and precipitates the salts of the heavy metals. It decomposes
on evaporation, the colour changing through green and red into
brown and a noncrystalline residue being left.

If sinapin thiocyanate be boiled with baryta water or caustic
potash solution, it decomposes into thiocyanic acid, sinapic acid
and a base, which was named sinkalin by Babo and Hirsch-
brunn, but has since been identified as choline (Vol. III., Part
II., p. 72).

C 1G H 23 N0 5 ,HSCN + 2H 2 = HSCN + C n H 12 O 5 + C 15 H 15 NO 2 .

Sinapic acid, C n H 12 5 , is best prepared, according to Remsen
and Coale, by boiling sinapin with baryta water and decom-
posing the precipitate, which is formed, with hydrochloric acid.
It is only slightly soluble in cold water and alcohol, and crystal-
lizes from a hot solution in small, yellowish, transparent prisms,
melting at 192. Its alkaline solution rapidly turns green, red,
and brown in the air. The addition of alcohol to the freshly
prepared solution of the potassium salt precipitates it in
iridescent plates, which rapidly change after the removal of the
alcohol. Calcium chloride and barium chloride produce white
precipitates, and ferric chloride gives a rose-red or fine purple-
red precipitate, a partial reduction being also effected. Lead
salts added to a neutral solution of the acid produce a white
precipitate, which soon becomes green and then brown, while
the colourless precipitates yielded by the salts of silver and
mercury, are rapidly reduced ; the metal is immediately
separated from gold solutions.

The barium salt alone has been obtained in a condition
suitable for analysis by precipitating a solution of the acid,
neutralized by potash or ammonia, with barium chloride, or
more readily by boiling the acid with baryta water in absence
of air ; it has the composition C 11 H 10 Ba0 5 .

Babo says : " Since it is a matter of some difficulty to obtain
another salt of the acid in a state fitted for analysis, and I could
not spare too much material for this research, the question
whether the acid is mono- or dibasic must remain for the
present undecided."

This point was settled by Remsen and Coale, who heated
weighed amounts of the acid with calcium or barium carbonate
and determined the amount of metal which had entered into
solution; they found that sinapic acid is monobasic, and that
the normal barium salt has the formula (C n H n O 5 ) 2 Ba.






SINAPIC ACID. 377



The insoluble barium salt is therefore a basic compound,
corresponding to the basic salicylates, and sinapic acid should
therefore be a hydroxy-acid, as is proved to be the case by the
existence of the following compound.

Acetylsinapic acid, C 11 H 11 (C 2 H 3 O)O 5 , is obtained by boiling
the acid with acetic anhydride, and forms crystals, which are
soluble in hot water and melt at 281.

When sinapic acid is heated on platinum foil, vapours are
given off which smell like incense, and are also formed when
the acid is fused with caustic potash, pyrogallol being among
the products.

According to Rernsen and Coale, sinapic acid is probably
butylenegallic acid :

OH



C 6 H 2 <
MX \CO.OH.

If this view be correct, the following formulae will represent
the constitution of sinapin and its thiocyanate :

/OH



62

XX \CO.OC 2 H 4 N(CH 3 ) 3 OH.

XX /OH

C 4 H 8 < >C 6 H 2 <

MX \OO.OC 2 H 4 N(CH 3 ) 3 S.CN.

If it be further assumed that sinalbin contains two molecules
of water of crystallization, its constitution may be represented
as follows :

,0. /OC 6 H n 5

C 4 H / >C 6 H 2 <

' XK ' \CO.O.C 2 H 4 (CH 3 ) 3 NO.SO 2 .OC 6 H 4 .CH 2 .NCS.

Gallocyauin. This dye, which was discovered by Kochlin,
and which is also known as solid-violet (violet solide), is manu-
factured by heating nitrosodimethylaniline hydrochloride with
gallic acid or tannin in alcoholic solution. It is a crystalline
substance with a green metallic lustre, readily dissolves in
alkalis, and yields salts which crystallize well, that with aniline
forming small, green crystals. Gallocyanin forms a blue solution
in concentrated sulphuric acid. It is used for dyeing cotton
and in calico printing, since it forms a beautiful violet-black



378 AROMATIC COMPOUNDS.

lake with chromium oxide, with which the material is mordanted.
The shades produced are as bright as those of aniline violet, but
much more stable towards light, alkalis and acids. In the
presence of quercitron or similar yellow dyes, dark blue shades
resembling indigo are produced and can be varied to the
greenest shades of blue.

It dyes silk and wool directly violet blue, and is also used as an
acid blue on azo-colours ; the goods arc dyed in ponceau or some
other shade, and the pattern is then printed on in the shape of
a mixture of solid-violet, indophenol and an alkaline reducing
agent, which effects the usual decomposition of the azo-colour,
while the blue colours are reduced to leuco-compoun'ds, which
penetrate the fibre and on exposure to air produce a fast blue
on a red ground. 1

Gallocyanin belongs to the class of the indophenols, but its
analysis has not yet been published. Its method of formation
leads to the following constitution or some similar one.

1L /COM

>C=:C<
0=C/ \fcN.C c H 4 .N(CH 3 ) 2 .

OH/ \)H



PYROGALLOLCARBOXYLIC ACID.

2206 This compound is formed, together with gallocarboxylic
acid, C ? H(OH) 3 (C0 2 H) 2 , 2 by heating pyrogallol to 130 with
ammonium carbonate, or more simply by heating pyrogallol in
an open flask with a concentrated solution of acid potassium
carbonate. 3 It crystallizes from hot water in silky needles of the
composition 3C 6 H 2 (OH) 3 CO 2 H + H 2 0, which become anhydrous
at 110 and have a markedly acid taste. One part dissolves at
12'5 in 767 parts of water ; it is readily soluble in alcohol, but
less so in ether. On heating in a current of hydrogen, a gradual
evolution of carbon dioxide accompanied by fusion sets in at
195 200, while it sublimes slowly, but without decomposition,
in a current of carbon dioxide. Its aqueous solution is coloured

1 Kochlin, Chcm. News, xlvii. 170; Pabst, Bull. Soc. Chim. xxxviii. 162;
Chcm. Zc.it. ix. 1444.

2 Senhofer and Brunner, Moncttsh. Chcm. i. 468.

3 Kostanecki, Btr. Dcuisdi. Clwm, Gfes. xviii. 3202.



PYROGALLOL CARBOXYLIC ACID. 379

violet by very dilute ferric chloride, while a strong solution pro-
duces a greenish brown c olouration ; ferrous sulphate produces no
immediate colouration, but the liquid becomes violet on stand-
ing. The same colouration is produced by concentrated sulphuric
acid which contains a trace of nitric acid.

Baryta water and lime water produce blue precipitates which
arc at first so finely divided that the liquid appears clear. The
acid is coloured dark brown by strong potash solution, especially
on boiling. It reduces aminoniacal silver solution in the cold
and im parts a green colour to Folding's solution, reduction taking
place on warming.

It differs sharply from gallic acid in remaining unacted on
by sulphuric acid at 140, no rufigallic acid being formed ; de-
composition, accompanied by a violent evolution of gas, sets in,
however, at a higher temperature.

The Fyroyallolcarboxylatcs. The following salts are charac-
teristic :

Calcium pyroyallolcarboxylatc, (C 7 H 5 O 5 ) 2 Ca + 4H 2 0, separates
from a hot solution in hard, granular crystalline masses.

Jlxrmni pyroyallolcarloxylate, (G 7 H 5 O 5 ) 2 Ba + 5H.,O, crystallizes
from a hot solution in hard, yellow prisms.

llndc lead pyroyallolcarboxylate, C 7 H 2 Pb 2 5 + H 2 O, is a white,
iiocculent precipitate, which becomes anhydrous at 100.

Ethyl pyrogattolcarbovylate, 2C 6 H 2 (OH) 3 C0 2 .C 2 H 5 -i- 3H,O, is
insoluble in cold water, but readily in alcohol and ether, and
separates from a hot aqueous solution in crystals, which become
anhydrous over sulphuric acid or at 100, at which temperature
they commence to sublime, and then melt at 102. Ferric
chloride colours the aqueous solution greenish brown.

Truthylpyroyallolcarboxylic acid, C H 2 (OC 2 H 5 ) 3 CO 2 H. The
ethyl ether of this substance is prepared by heating the preceding
compound with caustic potash, ethyl iodide and alcohol. It is
an odourless, volatile liquid, which is readily decomposed by
alcoholic potash. 1 The free acid is slightly soluble in cold, more
readily in hot water and alcohol, and crystallizes in long, silky
needles, melting at 100'5. It was first obtained from triethyl-
laphnetic acid, C 6 H 2 (OC 2 H 5 ) 3 C 2 H 2 .C0 2 H, by oxidation with
potassium permanganate, its aldehyde C 6 H 2 (OC 2 H ft ) 3 CHO, being
simultaneously formed as an oily liquid which gradually solidifies
to a crystalline mass melting at 70. 2

1 Will and Albrcf.-lit, JJcr. Dcutsch. Chcm. Gcs. xvii. 2100.
" far. Dr'itwk. Chcm. Gc*. xvii. 1087.



AROMATIC COMPOUNDS.



PHLOROGLUCINOLCARBOXYLIC ACID.

This acid is obtained by heating phloroglucinol with acid potas-
sium carbonate and water to 130 . 1 It crystallizes in needles,
which contain a molecule of water and are only slightly soluble in
water, more readily in alcohol, very readily in ether and have an
acid taste. The water is lost at 100, carbon dioxide being also
slowly evolved. On boiling with water it is decomposed
smoothly into phloroglucinol and carbon dioxide. Its aqueous
solution is coloured an intense blue by ferric chloride, which
soon changes to dirty brown, and its alkaline solution turns
brown in the air.

When its alcoholic solution is saturated with hydrochloric
acid, carbon dioxide is evolved and phloroglucinol diethyl ether
is formed (Part III., p. 196).



HYDROXYQUINOLCARBOXYLIC ACID.

The following derivatives of this acid are alone known :

Tricthylhydroxyquinolcarboxylic acid, C 6 H 2 (OC 2 H 5 ) 3 CO 2 H, is
formed by the oxidation of the two isomeric triethylaesculetic
acids, C 6 H 2 (OC 2 H 5 ) 3 C 2 H 2 .CO 2 H, with potassium permanganate,
and crystallizes from hot water in fine needles, melting at 134.
Its aldehyde, C 6 H 2 (OC 2 H 5 ) 3 COH, is also formed and crystallizes
from alcohol in splendid pointed prisms, melting at 95.

Trimethylhydroxyguinolcarboxylic acid, C 6 H 2 (OCH 3 ) 3 C0 2 H,
resembles the ethyl compound and melts at 108 109 . 2

These compounds were at first considered as derivatives of
phloroglucinolcarboxylic acid. When the triethylcompound is
distilled with lime, however, a triethoxybenzene is obtained,
which melts at 34, and is therefore different from the triethyl
ether of pyrogallol or phloroglucinol, so that it must be that of
hydroxyquinol. 3

1 Bcr. Dcutsch. Chcm. Ges. xvii. 2103.

2 Will, ibid. xvi. 2112.

8 Will and Albrecht, ibid. xvii. 2108.



QUINIC ACID. 381



CONSTITUTION OF THE TRIHYDROXY-
BENZOIC ACIDS.

According to theory, six of these compounds can exist, but
only four are known :

Pyrogallolcarboxylic Phloroglucinolcarboxylic
Gallic acid. acid. acid.

C0 H C0 2 H C0 2 H



l OBOH



OH\ /OH \ /OH

OH OH OH

Hydroxyqninolcarboxylic acids.



C0H



|
OH



I I H

\/'OH HOW

OH



The constitution of gallic acid is determined by its formation
from bromoprotocatechuic acid and a-bromoresorcylic acid,
whence it also follows that pyrogallol is an adjacent trihydroxy-
benzene, and that in phloroglucinol the hydroxyls are symmetri-
cally arranged (Part III., p. 188). The latter can only yield
one carboxylic acid, so that the constitution of phloroglucinol-
carboxylic acid is determined ; this is confirmed by its formation
from daphnetic acid, in which a hydroxyl is known to be in the
ortho-position to the carboxyl.

The constitution of the hydroxyquinolcarboxylic acid from
aesculetic acid has not yet been determined.



QUINIC ACID, C 6 H 7 (OH) 4 C0 2 H.

2207 Count Claude dc la Garaye, in 1746, obtained a crystal-
line deposit l from the extract of Peruvian bark, which became
known as Sel cssentid de la Garaye. Hermbstadt of Berlin
showed in 1785 that this " Chinasalz " is a salt of lime, 2 and
Hofmann, an apothecary of Leer, in 1790 detected in it a
1 CMmie hydraulique, Paris, 1746, 114. " Crcll's Ann. ii. 115.



382 AROMATIC COMPOUND?.

characteristic acid, which lie named " Chinasiiure," l and which
was carefully investigated by Vauquelin in 180G, who called it
acide quinique? Its correct formula was determined by Liebig 3
and Woskresensky. 4

It occurs to the amount of 5 8 per cent, in true Peruvian
bark, combined with alkaloids and lime. Stenhouse 5 was unable
to obtain the slightest trace from the false China nova s. surina-
mcnsis (Buena magnifolid] ; but Hlasiwetz subsequently showed
that it is present, although only in small amount. 6 Zwenger
and Siebert have also detected it in bilberry leaves (Vac-
cinium Myrtillus)? and in coffee beans. 8 They obtained an
ounce of the acid from some baskets of bilberry leaves gathered
in May, and one variety of Java coffee yielded O3 per cent.
Loew discovered it in meadow hay, 9 which contains about O'G
per cent.

Calcium quinate was formerly a byproduct of the manufacture
of quinine, but is not obtained by the method now in use. 10 It
is prepared by treating the powdered bark for two or three days
with cold water, adding a little milk of lime to the extract, in
order to precipitate tanning matters and the small quantity of
alkaloids present, and evaporating the nitrate until it has the
consistency of syrup. The calcium quinate which separates out
after some weeks is purified by re-crystallization and decom-
posed by sulphuric or oxalic acid.

Quinic acid crystallizes in hard, transparent, monoclinic prisms
or tablets, has a very sour taste, and dissolves at 9 in 2'5 parts
of water, more readily in alcohol, and scarcely at all in ether.
It is optically active and its aqueous solution is laivorotatory.

When it is heated it melts at 161'G , 11 and loses water at a
higher temperature, forming quinide, C 7 H 10 O 5 , which separates
from water in crystals resembling those of salammoniac, which
have an acid reaction and combine with bases to form salts
of quinic acid. 12 It probably has the following constitution,
C 8 H 7 (OH) 4 CO.OC fl H 7 (OH) 3 CO 2 H.

Quinic acid decomposes on dry distillation with formation of
phenol, quinol, catechol, benzoic acid and other products. 13






Crdl's Ann. ii. 314.
Ann. Chem. Pharm. vi. 14.
Ibid. liv. 100.
Ibid. cxv. 108.
Journ. Prakt. Chem. [2] xix.
Hesse, Ann. Chem. Plumn.
Hesse, ibid. ex. 335.


- Ann. Chim. lix. 162.
4 Ibid. xxiv. 257.
6 Ibid. Ixxix. 144.
8 Ibid. Suppl. i. 77.
309. 10 Neues HandwSrterb. ii.
cxiv. 292.
J3 Wohler, ibid. Ii. 146.


532.



QUTN1C ACID.



When lead dioxide is added to its aqueous solution, carbon
dioxide is evolved and the reaction may be carried on by
heating the mixture, lead quinate and quinol being formed : 1

C 7 H 12 G +0 = C 6 H 6 2 + CO,+3H 2 0.

When it is heated with manganese dioxide and sulphuric
acid, quinone is formed, while protocatechuic acid may be
obtained by evaporating a solution of the acid to which bro-
mine has been added, 2 or by fusing the acid with caustic
potash, 3 or caustic soda, 4 as well as, together with a large
amount of benzoic acid, by heating quinic acid to 150 with
fuming hydrochloric acid. 5

Fuming hydriodic acid reduces it at 120 to benzoic acid :

C 7 H 12 +2HI = C 7 H 6 2 +4H 2 + I 2 .

On heating with concentrated hydrochloric acid to 140 150,
parahydroxybenzoic acid and quinol are formed ; it dissolves
when heated with sulphuric acid with evolution of carbon dioxide
and formation of quinoldisulphonic acid (Hesse). Phosphorus
chloride converts it into metachlorobenzoyl chloride (Griibe) :

C 7 H 12 6 + 5PC1 5 = C 7 H 4 C1 2 + 5POC1 3 + 8HC1.

It is converted by the animal organism into hippuric acid
(Lautemann).

The whole behaviour of quinic acid points to the fact that it
belongs to the aromatic addition-products. 7 It is tetrahydroxy-
hexhydrobenzoic acid, and, since it is optically active, must
con cain an asymmetric carbon atom, so that it has the following
constitution :



H 2 C| jCH.OH
HO.HC, ^CH.OH
CH



; Hesse, Ann. Chan. Phnrm. cxiv. 292. '' Hesse, ibid. cc. 239.

'* Griibe, ibid, cxxxviii. 203. 4 Hesse, loe. cit.

5 Fittig and Hillebraml, ibid, cxciii. 197. 9 Ibid. cxxv. 9.

7 Griibe, Ann. C'Jiem. Pharm. cxlvi. 66.



AKOMATIC COMPOUNDS.



It differs from quercitol (Part III. p. 207) in containing a
carboxyl in the place of one hydroxyl. A different formula has
been proposed by Lieben, who found that quinic acid yields
iodoform when treated with iodine and caustic potasli ; he
therefore assumes that its constitution must be expressed by
the following or some similar formula : l

HO.CH CH 3
HO.C CH.OH

HO.CH CH.C(XH.



The Quinates. The salts of quinic acid are for the most part
readily soluble in water, slightly in alcohol, and crystallize well.
They have been investigated by Baup, 2 Woskrensky, Hesse, and
Clemm. 3

Sodium quinate, C 7 H n O 6 Na + 2H 2 O, crystallizes in large,
nacreous, rhombic prisms.

Clemm was unable to obtain the potassium and ammonium
salts in crystals ; their solutions only gave syrupy residues on
evaporation over sulphuric acid.

Calcium quinate, (C 7 H n O 6 ) 2 Ca 4- 10H 2 O, forms silky, rhombic
plates, or long, concentrically-grouped prisms, which dissolve at
10 in 6 parts of water and are insoluble in absolute alcohol.

Barium quinate, (C 7 H n O ) 2 Ba + 6H 2 O, crystallizes, according
to Henry and Plisson, in acute octohedral pyramids, while Baup
always obtained it in dodecahedra formed by the combination of
two pointed pyramids, and Clemm only as a partially crystalline
mass.

Lead quinate, (C 7 H n O 6 ) 2 Pb, crystallizes in readily soluble
needles ; ammonia added to its solution produces a voluminous,
hydrated precipitate which has the formula C 7 H 8 O c Pb 2 , after
drying at 200.

Silver quinate, C 7 H u O 6 Ag, forms warty crystals, which readily
dissolve in water and blacken in the light.

Copper quinate, (C 7 H n O 6 ) 2 Cu + 5H 2 O, crystallizes in light
blue plates.

Basic copper quinate, C 7 H 10 O 6 Cu + 2H 2 O, is obtained by boiling
the aqueous solution of the acid with an excess of copper oxide ;

1 Ann. Chem. Pharm. Suppl. vii. 232.

2 Ibid. vi. 1 ; Ann. Chim. Phys. [2] li. 56.

3 Ann. Chem. Pharm. ex. 345.



ETHYL QUINATE.



it forms small, green crystals, which are only slightly soluble in
cold water.

Ethyl quinate, C 6 H 7 (OH) 4 C0 2 .C.2H 5> was obtained by Hesse by
the action of ethyl iodide on the silver salt ; it is a viscid mass,
which is readily soluble in water and alcohol, and has a very
bitter taste.

Ethyl tetracetylguinate, C 6 H 7 (OCO.CH 3 ) 4 CO.OC 2 H 5 , is formed
by boiling the ethyl ether with acetic anhydride, and crystallizes
from boiling water in plates ; it separates from ether in large,
rhombic crystals which melt at 135, and sublime without
decomposition (Fittig and Hilldebrand).



v<>r.. in. PART iv



AROMATIC COMPOUNDS.



THE XYLENE GROUP.

2208 It has been already mentioned under benzene (Part III.
p. 77) that Mansfield in 1848 discovered that coal-tar naphtha
contains, besides benzene, its homologues ; of these he isolated
the following (0 = 6):

Boiling-point.

Toluol, C 14 H 8 about 113.

Cumol, CjgHj, 143 145.

Cymol, C M H, 4 170 172.

He adds, it is interesting to note, " that tar-oil contains
among its constituents the only four known members of the
series C 6 +n(C 2 H ). It seems, therefore, not improbable that
the gap \vhich still exists in this series (n = 5), corresponding to
a substance whose boiling-point lies between those of toluol
and cumol, will be filled by a compound to be obtained from
tar-oil. 1

Soon after this, Cahours discovered xylol (zyldne),CJ3. lo (C = 12),
boiling at 128 130, along with toluol in crude wood-spirit
(%v\ov, wood), 2 and Vdlkel found the same hydrocarbons in
wood-tar. 3 Church then stated that xylol is also contained
in coal-tar oil, and boils at 126'2, 4 whereas Ritthausen 5 and
Hiltenkamp 6 could only detect in it the hydrocarbons already
discovered by Mansfield.

Warren de la Rue and H. Mliller then showed that Rangoon
tar contains benzol and its homologues, which they were
unable to isolate, but recognised by conversion into their
characteristic nitro- compounds. 7 Shortly before this time,
Bussenius and Eisenstuck had investigated the rock oil from

1 Ann. Chem. Pharm. Ixix. 162. "- Ibid. Ixxiv. 168 ; Ixxvi. 236.

3 Ibid. Ixxxvi. 331. * Phil. Mag. [4] ix. 256.

8 Journ. Prakt. Chem. Ixi. 74. Ann. Chem. Pharm xcv. 89.
7 Journ. Prakt. Chem. Ixx. 300.



THE XYLENE GROUP. ' 387

Sehnde in Hanover, and discovered in it a new hydrocarbon,
which they called petrol, C 8 H 10 , its existence being proved by its
characteristic trinitro-derivative ; l and Hugo Miiller then showed
that the hydrocarbon obtained from coal-tar and boiling at 140
is not cumol, but xylol, which also occurs in the oils from
Burmah and Sehnde, trinitropetrol being identical with trinitro-
xylol. 2 In spite of this Bechamp repeated the statement that
xyloi boils at 126 130, adding that coal-tar also contains a
"new" hydrocarbon boiling at 139 140 . 3

Mansfield's cumol was subsequently proved to be a mixture
of trimethylbenzenes.

After Fittig and Tollens had made the important discovery
that the synthetic methylpheriyl or methylbenzol is identical with
toluol, 4 it was supposed that ethylphenyl or ethylbenzol would
be identical with xylol. This, however, was found not to be
the case, since it boils as much as 7 lower than the latter, and
does not yield a crystallized trinitro-derivative.

Beilstein then investigated xylol more carefully ; he fully con-
firmed Miiller's observations and found that on oxidation with
chromic acid it yields dibasic terephthalic acid, C S H 6 4 . 5 About
this time Fittig prepared methylbeuzyl, which he considered to
be identical with xylol, by the action of sodium on a mixture
of bromotoluol and methyl iodide. 6 He also found that ethyl-



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