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crystalline plates melting at 136, which are slightly soluble in
water, more readily in alcohol. A solution of this compound in
the necessary amount of caustic potash yields on evaporation a
residue from which alcohol extracts the compound C 6 H 4 (CH 3 )
SO 2 .NHK+H 2 O, crystallizing in needles. 2

Toluenemetasulphonic acid, C 6 H 4 (CH 3 )S0 3 H-fH 2 O, forms very
deliquescent, thin crystalline crusts.

Toluenemetasulphonic chloride, C 6 H 4 (CH 3 )S0 2 C1, is an oily
liquid.

Toluenemetasulphonamide, C 6 H 4 (CH 3 )SO 2 .NH 2 , crystallizes in
long plates melting at 1.07- 108.

Toluene-orthosulphonic acid, C 6 H 4 (CH 3 )S0 3 H+2H 2 O, forms thin
deliquescent plates ; the chloride is an oily liquid, and the amide
crystallizes in quadratic pyramids or prisms, which are almost
insoluble in cold water, and only slightly soluble in alcohol.

The salts of the three acids as a rule crystallize well (Claesson
and Wallin).

1 Miillcr, Ber. Dcutsch. Ckcm. Ges, xii. 1348.

- Hakanssou, ibid. v. 1084 ; Claesson and Berg, ibid. xiii. 1170.



AROMATIC COMPOUNDS.



TOLUENEDISULPHONIC ACIDS, C 6 H 3 (CH 3 )(SO 3 H) 2 .

2029 a-Toluenedisidphonic acid (CH 3 : SO 3 H : SO 3 H=1 : 2 : 4),
is a thick liquid which can be heated above 100 without de-
composition ; it may be prepared by heating toluene, or its ortho-
and para-sulphonic acids with fuming sulphuric acid, 1 as well as
by passing toluene vapour into concentrated sulphuric acid
heated to 240 . 2 Its amide, C 6 H 3 (CH 3 )(SO 2 .NH 2 ) 2 is tolerably
soluble in warm water, and crystallizes in prisms melting at
185 -186.

Senhofer and Forber, by heating toluene with a mixture of
sulphuric acid and phosphorus pentoxide, obtained a 7-toluene-
sulphonic acid, 3 which is, according to Claesson, identical with
the a-acid. 4

ft-Toluenedisulphonic acid is obtained in small quantities in
the preparation of the a-compound, and is also formed when
toluenemetasulphonic acid is treated with fuming sulphuric acid
(Hakansson). Its amide melts at 224 (Claesson).

y- Toluene disulphonic acid (1:3: 5). When orthotoluidine is
heated with fuming sulphuric acid or with chlorosulphonic acid,
toluidinedisulphonic acid (CH 3 : NH 2 : S0 3 H : SO 3 H = 1:2:3:5)
is formed ; this yields a crystalline diazo-compound, CH 3 .C 6 H 2
(N 2 SO 3 )SO 3 H, which is, according to Neville and Winther, con-
verted into the toluenedisulphonic acid by heating with absolute
alcohol under pressure, 5 while Limpricht and Basse observed
that ethoxytoluenedisulphonic acid, CH 3 .C 6 H 2 (OC 2 H 5 )(SO 3 H) 2
is thus formed. In order to obtain the former, the diazo-com-
pound is converted into iodotoluenedisulphonic acid, and this
heated with concentrated hydriodic acid.

7-Toluenedisulphonrc acid forms an amide which crystallizes in
small lustrous plates melting above 240 . 6



TOLUENETRISULPHONIC AdDS, C 6 H 2 (CH 3 )(S0 3 H) 3 .

Only one of the six toluenetrieulphonic acids which are theo-
retically possible is known ; it is obtained by gradually heating

1 Hakansson, Ber. Deutsch. Chcm. Ges. \: 1084 ; Claesson and Bey, ibid. xiii.
1170.

2 Gnehm, ibid. x. 542 ; see also Fahlberg, ibid. xii. 1052.

3 Ann. Ckem. Pharm. clxiv. 226.

Ber. Deutsch. Chem. Ges. xvii. Ref. 284.

8 Hid. xv. 2993. s Im , xviii . 2177.



THE CRESOLS. 23



potassium a-toluenedisulphonate with three molecules of chloro-
sulphonic acid to 240, until the product forms a clear solution
in water. The barium salt is then prepared, and from this
the potassium salt, which is converted by the action of phos-
phorus pentachloride into toluenetrisulphonic chloride, C 6 H 2
(CH 3 )(SO 2 C1) 3 , which crystallizes from chloroform in rhombic
tablets melting at 153. On heating with water to 130 140
the free acid is obtained ; it crystallizes with six molecules of
water in long, fine needles. 1



MONOHYDROXYTOLUENES AND ALLIED
BODIES.

CH 3
THE CRESOLS, C 6 H/

\OH.

2030 In 1851 Stadeler discovered in the urine of fche cow,
together with phenylic acid, a very similar body which he named
Taurylic acirf, and considered to be the next higher homologue of
phenylic acid. 2 As the question was subsequently raised whether
the creosote discovered by Reichenbach in wood-tar is identical
with phenol or not, Fairlie, under Williamson's directions, con-
ducted an investigation on the so-called coal-tar creosote (Part
III. p. 70) and found in it " hydrate of cresyl," C 7 H 8 O, the
homologue of phenyl hydrate ; he describes this compound as a
strongly refractive liquid smelling like phenol and boiling at
203, and investigated its properties with some care. 3 Duclos
discovered the same compound in tar from pine-wood 4 and
Marasse in that from beech-wood. 5

Griess obtained cresol or cresyl alcohol artificially by boiling
diazotoluene nitrate with water, 6 and Wurtz by fusing toluene-
sulphonic acid with caustic potash. 7

Engelhardt and Latschinow were the first to prove that three
isomeric cresols exist ; they obtained pure paracresor, or, as
they called it, a- cresol, by fusing tolueneparasulphonic acid with
caustic potash, and from ordinary toluidine by Griess' reaction.
By the same reactions they prepared /3-cresol from the ortho-

1 Claesson, Ber. Deutsch. Chem. Ges. xiv. 307.

- Ann. Chem. Phnrm. Ixxvii. 188.

3 Chem. Soc. Journ. vii. 232. * Ann. Chem. Phnrm. cix. 135.

5 Ibid. clil. 64. Jahresber. 1866, 458.

7 Ann. Chem. Pharm. cxliv. 1^1.



24 ABOMATIC COMPOUNDS.

sulphonic acid and pseudotoluidine (orthotoluidine), but they
did not obtain it in a pure state. They further found that
thymol, C 6 H 3 (GH 3 )(C 3 H 7 )OH, on heating with phosphorus pent-
oxide, decomposes into propylene and y-cresol. 1 This metacresol
was then obtained in larger quantities by Oppenheim and Pfaff
by heating hydroxyuvitic acid with lime. 2

Kekule obtained pure orthocresol by acting with nitrous acid
on orthotoluidine and by heating carvacrol (cymophenol), an
isomeride of thymol, with phosphorus pentoxide. 3

The constitution of the three cresols was determined with
certainty by Earth, who showed that on fusion with caustic
potash, orthocresol is oxidized to salicylic acid, metacresol to
hydroxybenzoic acid, and paracresol to parahydroxybenzoic acid
(Part III. p. 45). 4

Further investigations have shown that the cresol contained
in coal-tar is a mixture of the three isomerides. 5 It is obtained
from the oily mother-liquor left after crystallization of the
phenol by dissolving in caustic soda, removing all naphthalene
by a current of steam, and then fractionally precipitating the
solution with hydrochloric acid ; the cresol separates out first,
the phenol, being a stronger acid, remaining in solution. 6 Ac-
cording to another method, the solution is neutralized with
hydrochloric acid and the mixture agitated with sufficient
baryta water to dissolve all the phenol. 7 The cresol obtained
is purified by distillation until it boils at 198 -203. Deriva-
tives of all three cresols can be prepared from it, but only the
para-compound can actually be extracted in the pure condition.
This is effected by treating the mixture with benzoyl chloride,
paracresyl benzoate, melting at 78, being formed ; this is sepa-
rated by pressing from the liquid ethers of the two other cresols,
purified by re-crystallization, and decomposed by caustic soda
(Engelhardt and Latschinow). Baumann has pointed out that
the cresol (taurylic acid) contained in the urine of graminivora
occurs as the potassium salt of paracresylsulphuric acid. 8 This
compound also occurs in human urine during scarlatina, ery-
sipelas, &c. 9 The urine of horses also contains some orthocresyl

1 Zeitxchr Chem. 1869, 618.

* Ber. Deutsch Chem. Gcs. viii. 884.
3 Ibid. vii. 1006.

* Ann. Chem. Pharm. cliv. 356.

* Schotten and Tiemann,' Ber. Deutsch Chem. Gcs. xi. 783.
" Miiller, Zeitschr. Chem. 1865, 271.

7 Ihle, Journ. Prakt. Chem. [2] xiv. 442.

8 Ber. Deutsch. Chem. Gcs. ix. 1389, 1716.
51 Brieger, Hoppe-Seyler's Zeitschr. iv. 204.



ORTHOCRESOL. 25



sulphuric acid. 1 Para- and ortho-cresol are also formed when
the liver of the horse is caused to putrefy with the addition of
river-mud. 2

2031 Orthocresol is best obtained by adding 12 parts of pure
potassium nitrite to a solution of 15 parts of orthotoluidine and
15 parts of sulphuric acid in 500 parts of water; the liquid is
heated by a current of steam, and the cresol distilled off in the
steam. 3 It forms colourless crystals, melts at 30 and boils at
188. Its aqueous solution is coloured blue by ferric chloride ;
on fusion with caustic potash it is oxidized to salicylic acid.
When administered to a dog it appears in the urine as ortho-
cresylsulphuric acid and oxycresylsulphuric acid (hydrotolu-
quinonesulpliuric acid). By the action of potassium chlorate
and hydrochloric acid it yields di- and tri-chlorotoluquinone. 4

Orthocrcsyl oxide, (CH 3 .C 6 H 4 ) 2 O. If a few grains of iodine and
then some aluminium are added to boiling orthocresol, alu-
minium orthocresylate, (CH 3 .C 6 H 4 0) 6 A1 2 , is formed, and this
solidifies on cooling to a black vitreous mass. When subjected
to dry distillation it yields, among other products, orthocresol
and orthocresyl oxide, which is a colourless liquid smelling like
the geranium, and boiling at 272 9 -278. 5

Dicklororthocrcsol, C 6 H 2 C1 2 (CH 3 ).OH, is obtained by the action
of chlorine on boiling orthocresol ; it crystallizes from alcohol in
needles with a silky lustre, melts at 55 and on oxidation under-
goes partial combustion, at the same time yielding trichloro-
toluquinone. 6

Broinorthocresol, C 6 H 3 Br(CH 3 )OH, has been prepared from
bromorthotoluidine, and crystallizes from alcohol in lustrous
golden needles melting at 88'5. 7

a-Nitro-orthocresol, C 6 H 3 (CH 3 XN0 2 ) OH (1 : 3 : 2), is formed
when a solution of 2 parts of orthocresol in 2 parts of glacial
acetic acid is allowed to drop into a cold mixture of 3 parts of
nitric acid, of specific gravity 1'4, and 6 parts of glacial acetic
acid. It is insoluble in water and crystallizes from dilute
alcohol in long, yellow prisms melting at 69'5. Its potassium
salt crystallizes in garnet-red, rhombic tablets.

When the hydrochloride of the amidocresol obtained from

Preusse, ibid. il. 355 ; Ber. Deutsch. Chcm. Gcs. xi. 1911.

Baumann and Brieger, Hoppe-Seyler's Zcitschr. iii. 149, 252.

Schotten and Tiemann, loc. cit.

Routhworth, Ann. Chem. Pharm. clxviii. 273.

Gladstone and Tribe, Journ. Chcm. Soc. 1886, i. 25.

Claus and Riemann, Bcr. Deutsch. Chcm. Gcs. xvi. 1598.

"VVroblevsky, Ann. Chcm. Pharm. clxviii. 165.



26 AROMATIC COMPOUNDS.

this compound is distilled with sodium formate, a methenyl
compound is formed ; this reaction is characteristic of all the
amidophenols in which the amido-group is in the ortho-relation
to the hydroxyl. 1

Methenylamidorthocresol is formed according to the following
equation :

,NH, /N.

CH 3 .C 6 H 3 < + CHO.OH = CH 3 .C H/ >CH + 2H 2 O.

X)H \Q/

It is a crystalline mass which melts at 38 39, boils at 20(T
and has a peculiar smell, resembling that of acetamide, charac-
teristic of these anhydro-bases.

A liquid nitrocresol boiling at 226 230 is formed together
with the solid compound. 2

fi-Nitro-ortlwcresol (1 : 5 : 2) is prepared from the corresponding
nitro-orthotoluidine by means of the diazo-reaction or by heating
it with strong caustic soda. It crystallizes in fine, light yellow
needles and melts at 95. 3 On reduction it yields /3-amido-
orthocresol, the hydrochloride of which crystallizes readily.

<y-Nitro-ortkocresol (1 : 4 : 2) is formed together with the a-com-
pound when orthocresol is nitrated at as low a temperature as
possible. On distillation with steam it remains behind. It is
only very slightly soluble in water, readily in alcohol and ben-
zene, and crystallizes in white needles united to form bushy
aggregates, or * n small, hexagonal tablets, being, therefore,
dimorphous like paranitrophenol. It melts at 82 85, and
forms a potassium salt, crystallizing in small brass-yellow
plates. On reduction it is converted into 7- amldo-orthophenol,
crystallizing in tablets which have a silvery lustre and melt at
175. When oxidized in an acid solution, it is converted into
toluquinone. Hirsch has been unable to obtain the liquid nitro-
cresol mentioned above. 4

Dinitro-orthocresol, C 6 H 2 (CH 3 ) (NOg) 2 OH (1 : 3 : 5 : 2), was
first obtained from orthotoluidine, nitro-orthotoluidine (NH 2 :
NO 2 = 2 : 5), and orthotoluidinesulphonic acid (NH 2 : SO 3 H =2:3),
by converting them into diazo-compounds and heating these with
dilute nitric acid. 5 It is also formed by the further nitration of

' Ladenburg, Her. Deutsch. Chcm. Ges. ix. 1524; x. 1124.
' Hofmann and Miller, ibid. xiv. 467.
3 Neville and Winther, ibid. xv. 2978

Hirsch, ibid, xviii. 1511.
5 Neville and Winther, ibid. xiii. 1496 ; Nolting, and Sails, ibid. xiv. 987.



METACRESOL. 27



a- and y-nitro-orthocresol (Hirsch), and of orthocresyl ether. 1
It crystallizes from alcohol in long, yellow prisms, and from
petroleum-spirit in broad, golden-yellow needles, which have a
blue surface-lustre and melt at 86.

On the reduction of its ethyl ether the diamido-ether is
obtained, and this compound forms a chrysoidine with diazo-
benzene (Part III. p. 301), thus affording a further proof that the
nitroxyl groups in dinitrocresol have the meta-relation to each
other.

2032 Metacresol. In order to prepare this compound, 100
grammes of thymol are heated for ten or twelve hours with 35
grammes of phosphorus pentoxide, the propylene which is
evolved being passed into bromine in order to obtain its bromide
as a by-product. The syrupy mass is brought into 115 120
grammes of fused caustic potash, and the mixture kept in a
state of fusion and well agitated for five or ten minutes. It is
then dissolved in water and extracted with ether in order to
remove cresyl phosphate and other substances ; the residue is
then decomposed with hydrochloric acid, the metacresol taken
up with ether, the latter distilled off, and the product purified
by distillation in a current of carbon dioxide (Schotten and
Tiemann).

It is a liquid which smells like phenol, boils at 201 and does
not solidify in a freezing mixture ; if, however, a crystal of phenol
be thrown into the cooled liquid it solidifies immediately, form-
ing crystals resembling those of phenol and melting at 3 4. 2
Its aqueous solution is coloured violet to blue by ferric chloride ;
by the action of potassium chlorate and hydrochloric acid, it is
converted into dichlorotoluquinone (South worth).

Metacresyl oxide, (CH 3 .C 6 H 4 ) 2 O, is formed, together with pro-
pylene and other products by the dry distillation of aluminium
thymol, (C 3 H 7 (CH 3 )C 6 H 3 0) 6 A1 2 , and is a liquid boiling at
284 288 . 3

Bromometacresol, C 6 H 2 Br(CH 3 )OH (1:3: 5), has been pre-
pared from the corresponding bromotoluidine, and crystallizes
from hot water in white needles melting at 56 57. 4

Nitrometacresol, C 6 H 3 (CH 3 )(NO 2 )OH (1 : 3 : 5), is prepared
from symmetric dinitrotoluene ; it crystallizes from hot water in
light yellow, lustrous prisms, containing one molecule of water

1 Stadel, Ann. Chem. Plmrm. ccxvii. 158.

- Stadel, Bcr. DeMsch. Chem. Ges. xviii. 3443.

3 Gladstone and Tribe, Journ. Chem. Soc. 1882, i. 5.

4 Seville and Winther, Bcr. Deutsch. Cham. Gcs. xv. 2991.



28 AROMATIC COMPOUNDS.



of crystallization. It is deposited from solution in benzene in
anhydrous crystals melting at 90 91. On reduction it yields
amidometacresol, the hydrochloride of which is readily soluble. 1

Trinitrometacresol, C 6 H(NO 2 ) 3 (CH 3 )OH (NO 2 : NO 2 : NO 2 = 2 :
4 : 6), was obtained by Duclos from crude cresol ; N biting and Salis
have prepared it from metacresol, which is readily converted into
the trinitro-compound, while its isomerides yield the dinitrocresols
as final products. In order to prepare it, coal-tar cresol is
dissolved in 3 parts of concentrated sulphuric acid, and allowed
to stand in a warm place until cresol no longer separates Out on
the addition of water. Crude nitric acid is then gradually
added to the aqueous solution, which is subsequently evaporated,
the residue being extracted with a little water to remove picric
and oxalic acids, and repeatedly re-crystallized from alcohol. 2

Liebermann and van Dorp obtained it by heating nitrococ-
cussic acid, 3 C 6 (NO 2 ) 3 (CH 3 )(CO 2 H)OH, and Emmerling and
Oppenheim by the action of nitric acid on hydroxyuvitic acid,
C 6 H 2 (CH 3 )(CO 2 H) OH. 4 Trinitrometacresol is slightly soluble
in cold, somewhat more readily in hot water, and crystallizes in
long, yellow needles melting at 105 106.

When its ethyl ether is heated with alcoholic ammonia, no
nitrous acid is removed (Nolting and Salis), which proves that it
contains no nitroxyl groups in the ortho-relation (Part III.
p. 73), and, therefore, that trinitrometacresol has the following
constitution :

CH 3



2033 Pamcresol is most readily obtained from paratoluidine, as
orthocresol is from orthotoluidine ; it crystallizes in prisms melting
at 36, and boils at 198 ; its aqueous solution is coloured blue
by ferric chloride. It differs from its isomerides in not yielding
a chlorinated toluquinone by the action of potassium chlorate and
hydrochloric acid.

Paracresyl oxide (CH 3 .C 6 H 4 ) 2 0, has been prepared by
Gladstone and Tribe in the same manner as the ortho-compound,

1 Ber. Deutsch. Chcm. Ges. xv. 2978.

2 Beilstcin and Kellner, Ann. Chem. Pharm. cxxviii. 165.

3 Ibid, clxiii. 101.

4 Ber. Deutsch. Chem. Ges. ix. 1094.



PAEACRESOL. 29



a,nd is also formed by heating paracresol to 300 with zinc chloride.
It crystallizes from alcohol in small lustrous plates, and from
petroleum spirit in needles which have a silky lustre, and melt
at 165, but readily volatilize at 100 . 1

Chloroparacresol, C 6 H 3 (CH 3 )C1(OH) (1:3: 4), is formed by
the action of dry chlorine on anhydrous sodium paracresate. It
is a colourless liquid which boils at 195 196, and has a peculiar,
unpleasant, persistent odour. Phosphorus pentachloride converts
it into a dichlorotoluene, which yields on oxidation the ortho-
ilichlorobenzoic acid melting at 200 . 2

Dichloroparacresol, C 6 H 2 (CH 3 )C1 2 .OH, is formed by the
action of chlorine on boiling paracresol; it crystallizes from
alcohol in monoclinic needles, and from a hot, concentrated
solution in petroleum-ether in long needles melting at 39 ; on
the gradual evaporation of a dilute solution, it is obtained in
transparent prisms with a melting point of 42 ; these, however,
soon fall to pieces, and the product then melts at 39. On
oxidation the dichlorobenzoic acid melting at 156 is formed
(Glaus and Riemann).

' Broinoparacresol, C 6 H 3 (CH 3 )Br(OH) (1 : 3 : 4), is obtained
by the action of bromine on potassium paracresate. It is a
liquid which does not solidify in a freezing mixture, boils at
213 214, and has a less unpleasant smell than the chlorine
compound (Schall and Dralle).

iJromoparacresol (1 : 2 : 4) may be readily obtained by the
action of bromine on a solution of paracresol in chloroform ; it
crystallizes in needles, melting at 17 18, and boils at
218 220. On fusion with caustic potash it is converted into
lutorcinol, C C H 3 (CH 3 ) (OH) 2 . 3

Dibromoparacresol, C 6 H 2 (CH 3 )Br 2 (OH), is also . formed when
potassium paracresate is treated with bromine. It crystallizes
from alcohol in prisms which are isomorphous with dichloropara-
cresol and melt at 49 (Schall and Dralle).

lod&paracresol, C 6 H 3 (CH 3 )I(OH) (1:3: 4), is an oily liquid,
and is obtained by the action of iodine on potassium paracresate ;
on fusion with potash it yields protocatechuic acid, C C H 3 (OH) 2
C0 2 H, and catechol.

Di-iodoparacresol, C C H 2 (CH 3 )I 2 (OH), is formed in the pre-
paration of the mono-compound, and crystallizes in small tablets
melting at 61'5 (Schall and Dralle).

1 Buch, Ber. Deutsch. Chem. Ges. xvii. 2638.

'" Schall and Dralle, ibid. xvii. 2528. 3 Vogt and Henninger, ibid. xv. 1081.



30 AROMATIC COMPOUNDS.

a-Nitroparacresol, C 6 H 3 (CH 3 )(N0 2 )OH (1:3: 4), is obtained
by boiling nitracetparatoluide with caustic soda, 1 and by the
nitration of paracresol. 2 It is slightly soluble in water, readily
in alcohol, and crystallizes in flat, yellow needles, which melt at
33'5, and are volatile in steam.

a-Amidoparacrcsol, C 6 H 3 (CH 3 )(NH 2 )OH (1:3:4) is formed
by the reduction of the nitro-compound with tin and hydro-
chloric acid ; it crystallizes from ether in monoclinic prisms, and
when heated with formic acid yields methenylamidoparacresol,
melting at 45 (Hofmann and Miller).

/3-Nitroparacresol, (CH 3 : N0 2 : OH = 1 : 2 : 4), is prepared from
ordinary dinitrotoluene by reducing it with ammonium sulphide
to nitrotoluidine and then replacing the amido-group by hy-
droxyl. It forms long yellow crystals which melt at 78 and are
readily soluble in hot water and alcohol. 3

P-Amidoparacr&sol, (CH 3 : NH 2 : OH = 1 : 2 : 4), is obtained
by the reduction of the preceding compound, and crystallizes
from hot water in small plates melting at 143 144 . 4

ry-Amidoparacresol, (CH 3 : NH, : OH = 1:4:2). The hydro-
chlorids of this base is obtained by converting the monacetyl
compound of the corresponding diamidotoluene into acetamido-
cresol, C 6 H 3 (CH 3 )OH(NH.C 2 H 3 O) and boiling this with hydro-
chloric acid. It crystallizes in small glistening plates, and on
treatment with potassium bicarbonate yields the free base,
which forms small lustrous plates or needles, melting at
159 161 (Wallach).

The constitution of the substituted paracresols follows from
their conversion into dihydroxytoluenes.

Dinitroparaeresol, C 6 H 2 (CH 3 )(NO 2 ) 2 OH(1 :3 :5 :4), has been
prepared from the corresponding dinitrotoluidine and by the
nitration of cresolsulphonic acid. 5 It is also obtained by warming
the diazo-compound prepared from paratoluidinesulphonic acid
with nitric acid (Neville and Winther), and by the nitration ol
paracresol ethyl ether; it crystallizes from dilute alcohol in
yellow needles melting at 85. On the reduction of its ethyl
compound, diamidoparacresyl ether, C 6 H 2 (CH 3 )(NH 2 ) 2 OC 2 H 5 , is

1 Wagner, Ber. Deutsch. Chem. Ges. vii. 537 ; Neville and Winther, ibid. xv.
2893.

2 Armstrong and Thorpe, Jahresb. Chem. 1876, 452 ; Hofmann and Miller,
loc. tit.

3 Knecht, Ann. Chem. Pharm. ccxv. 83 ; Ber. Deutsch. Chem. Ges. xv. 298.
Neville and Winther, ibid. xv. 2980

4 Wallach, ibid. xv. 2831.

5 Armstrong and Field, Ber. Deutsch. Chem. Ges. vi. 974.



DIHYDROXYTOLUENES. 31



obtained ; this compound forms a chrysoidine with diazobenzene
chloride, proving that the nitroxyls of the dinitrocresol are in
the meta-relation to each other.

Potassium dinitroparaeresate, C 6 H 2 (CH 3 )(NO2) 2 OK, crystallizes
in red needles and forms the "golden yellow," which was
exhibited as a new dye in the Belgian section of the Vienna
Exhibition in 1873. 1

It is also, together with the potassium salt of dinitro-ortho-
cresol, contained in " safronsurrogate," which is used for colouring
milk, butter, and cheese. 2

Victoria yellov: or aniline orange, which formerly came into
the market as a red powder, is the salt of a third dinitrocresol,
the constitution of which is unknown. It crystallizes from hot
water in yellowish needles, melting at 109 110. 3

T/iiocresols, C 6 H 4 (CH 3 )SH, are obtained by the reduction of

the corresponding sulphonic chlorides.

Melting- Boiling-
point, point.
Orthothiocresol 4 small, delicate plates . 15 188

Metathiocreso! 5 liquid * 188

Parathiocresol c large plates ' 43 189



DIHYDROXYTOLUENES AND ALLIED BODIES.

HOMOCATECHOL, OR HOMOPYROCATECHIN, C C H 3 (CH 3 )(OH) 2
(1:3:4).

2034 Hugo Muller obtained this compound by heating its
monornethyl ether, creosol, with hydriodic acid : 7

/CH 3 /CH 3

C C H 3 ^-OH + HI = C C H 3 ^-OH + CHJ.
'\OCH 3 \OH

It is also formed by fusing creosol with caustic potash, 8 by
boiling the diazo-compound of a-amidocresol with water (Neville

Piecard, Her. Dcutsch. Chem. Gcs. viii. 685.

Wichelhaus, ibid. vii. 770.

Marlins and Wichelhaus, ibid. ii. 206.

Hiibner and Post, Ann. Chem. Pharm. clxix. 30.

Ibid. 6 Miircker, ibid, cxxxvi. 79

Chem. News, x. 269.

Tiemann and Koppe, Her. Deutu-h. Chem. Ges. xiv. 202'..



32 AROMATIC COMPOUNDS.

and "Winther), and by submitting a-homoprotocatechuic acid,
C C H 2 (CH 3 )(OH) 2 C0 2 H, to dry distillation. 1

Homocatechol is a syrup which readily dissolves in water,
alcohol, ether, and benzene, and can be distilled without



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