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my opinion, consider it as certain that the Europeans, and first
the Florentines, were made acquainted with this dye-stuff and
its use in the beginning of the fourteenth century. At that
time the Italians brought from the East the seeds of many arts
and sciences, which, afterwards sown and nurtured in Europe,
produced the richest harvests ; and nothing is more certain than
that the art of dyeing was brought to us from the East by the
Italians. I do not believe that the merit of having discovered
this dye by the above-mentioned accident is due to that Floren-
tine ; but I am of opinion that he learned the art in the Levant,
and on his return taught it to his countrymen, which was doing
them no small service.

The archil lichens, the most valuable of which are Eocella tinc-
toria and R. fuciformis, occur in several varieties and in con-
siderable quantity on the coasts of warm and tropical countries,
such as the islands of the Mediterranean, the Canary and Cape
Verde Islands, Madagascar, Zanzibar, Angola, Ceylon, Java,
Peru, Chili, &c.

The old method for the preparation of archil consisted in
treating the lichens with stale urine and lime in large casks
provided with moveable lids, a considerable quantity of alum
and white arsenic being added to prevent the fermentation from
passing to a further stage. The mixture is well agitated for a
month and then stored in casks in which it is allowed to stand
for a long time before use, the colour being found to improve on

A more modern process consists in treating the finely-chopped
lichens with dilute ammonia, and keeping the mixture at the
temperature of the air or at a slightly higher one until a dark
violet paste has been formed ; this is diluted with ammonia and
filtered through a press ; the solution thus obtained is known as
blue archil. Red archil is obtained from this by gentle heating,
the ammonia being thus removed.

Stenhouse proposed first to extract the lichens with milk
of lime, precipitate the solution with hydrochloric acid and
work up the erythrin, &c., thus obtained as by-products, the

1 These documents from the Florentine records may be found in Dominid,
Marine Manni do Florcntinis Inventis Commcntarium. Ferrariae 1731. Beck-
inanu quotes the passage in question.


colouring matter being thus left in a much purer condition.
Marnas of Lyons found that the best results were obtained by
extracting with dilute ammonia and warming the compounds
precipitated from the solution with ammonia in a current of air
to 70 for about three weeks. On addition of calcium chloride
a precipitate, known as French purple (pourpre fran$aise), is
thrown down, and the material thus obtained yields much finer
and clearer shades than archil.

Since the discovery of the aniline dyes, archil has lost much
of its commercial importance ; it is now only used in combina-
tion with other colouring matters in order to obtain certain
shades of brown, and for the production of a cheap blue for wool
dyeing ; the material is first grounded with indigo and then dyed
with archil, the result being a dye which is similar to that of
genuine indigo-blue.

Cudbear or Persia. The inhabitants of Sweden, Scotland,
Ireland, Wales, &c., have for centuries been in the habit of
using various kinds of lichen, especially Lecanora tinctoria, for
wool-dyeing, the colour being produced by treatment of the
lichen with urine. During last century a patent was taken out
by Dr. Cuthbert Gordon for the preparation of cudbear, 1 by
drying and powdering the pasty mass obtained by the action of
ammonia or urine on the lichens. Cudbear is prepared in the
Auvergne from Variolaria orcina by a similar method.

Orceln. Robiquet has given this name to the colouring
matter of archil, which is formed, as he discovered, by the action
of hydrogen and ammonia on orcinol. 2 Gerhardt calculated its
formula from the analyses of Dumas and Kane, 3 and gave the
following equation for its formation :

C 7 H 8 2 + NH 3 + 30 = C 7 H 7 N0 3 + 2H 2 0.

Kane prepared orcein from commercial archil ; he describes it
as a carmine-red powder, containing carbon and nitrogen in a
constant ratio, while the amount of oxygen is variable, being
larger as the archil becomes older ; hence he assumed that it
consists of two similar colouring-matters, a-orcein and -orcein.

Liebermann, who obtained the colouring matter by the action
of gaseous ammonia and air on pure orcinol, found that two

1 Bancroft, Philosophy of Permanent Colours, 1813, i. 300.
Ann. Chim. Phys. Iviii. 320.
Ann. Chem. Pharm. xxxix. 25.


compounds are thus formed according to the ? following
equations :

2C 7 H 8 2 + NH 3 + 30 = C u H n NO a + 3H 2 6

C U H 13 N 4 + NH 3 + O = C U H 12 N 2 3 + 2H 2 O.

The latter is therefore formed in larger quantity when the
action of the ammonia is allowed to continue for some time ; it
is less soluble in aqueous ammonia and alcohol than the former
compound. Both occur as amorphous masses having a beetle-
green lustre, and forming splendid purple solutions with alkalis ;
but the solution of the second compound has a bluer shade than
that of the first. 1

2040 Litmus (tournesolso a^kmus)wd& discovered by the Dutch. 2
It is prepared from various species of Rocella, Variolaria and
Lccanora, by allowing them to ferment in contact with ammonia
and carbonate of potash; as in the manufacture of archil. When
the mass has become violet, stale urine, lime and potashes are
added, and the mass again allowed to ferment until it has as-
sumed a blue colour ; it is linen' mixed with gypsum or chalk,
and a little indigo, 3 and made up into small tablets.

Kane was the first more accurately to investigate litmus, and he
obtained several colouring matters and other substances from it. 4
Wartha, who also investigated the colouring matter of litmus,
found indigo in it ; this, however, had probably been purposely
added as just described, although it may possibly have been
derived from the urine, which is known to contain appreciable
quantities of a substance which yields indigo on decomposition.
On extracting litmus with cold alcohol, Wartha obtained a red
colouring matter which is indifferent towards acids, and yields
litmus blue and another substance when treated with water.
On evaporating the solution and treating the residue with
absolute alcohol and a little acetic acid, a scarlet colouring
matter is removed, and this is changed to a purple by ammonia,
while the pure litmus blue remains behind as a brown powder,
which forms a reddish brown aqueous solution turned blue by
the slightest trace of an alkali. 5

According to De Luynes, the pure colouring matter is obtained
by digesting 1 part of orcinol with 5 parts of ammonia and 25

1 Ber. Dcntsch. Chem. Ges. viii. 1649.

2 The origin of this name is unknown ; it may perhaps be derived from Lacca
musci, a lake prepared from moss. 3 Gottlieb, Chem. Tech. p. 531.

4 Loc. cit. 5 jj cr , Dcutsch. C'hcm. Gcs. ix. 217.


parts of crystallized carbonate of soda for four or five days at
60 80, and precipitating the solution with hydrochloric acid. It
is only slightly soluble in water, and the wine-red colour of this
solution is changed to bluish violet by alkalis, and to a reddish
brown by acids. It yields a red solution with alcohol, and a
yellow one with ether. De Luynes considers that the colouring
matter is a weak acid which forms blue salts, the potassium
salt existing in litmus. 1

Litmus is not only employed in the laboratory in the form of
litmus paper and tincture, but is also used for colouring wine
and vinegar. The colouring matter can readily be recognized by
its absorption spectrum ; ether extracts it from an acid solution
yielding a yellow liquid which absorbs the left end of the spec-
trum up to E \ D. A drop of ammonia colours the solution
blue, an absorption band being formed which begins at d, where
it is very intense, gradually diminishing to E. On shaking with
water the colouring matter is taken up, and the blue solution
gives an absorption band at D ; the addition of acid now chaages
the colour to brick-red, and the solution gives an absorption
spectrum similar to that of wine. 2

Ribbon Litmus (Tourncsollappen, tournesol en drapeaux, Bezetta,
Lackmus in Fleckchcn) is obtained in southern France from
the expressed sap of Croton tinctorium ; linen rags are soaked
in the sap, dried in the sun, and then exposed on heaps of
horse-dung covered with chopped straw, the ammonia evolved
being sufficient to change the colour of the rags, which are fre-
quently turned, to blue. They are then again dipped in the
sap, to which urine has been added, the colour thus produced
becoming dark green or purple-red on drying, and they are then
brought into the market. It was formerly believed that the
Dutch employed them for the manufacture. of litmus, but this is
not the case ; they are actually used to colour the exterior of
cheeses red.

The colouring matter contained in these ribbons has not been
accurately investigated; acids change it to red, but the blue
colour is not restored by alkalis.

1 Jahresber. 1864, 551.

2 Vogel, Spcctralanalysc, p. 269.


CRESORCINOL, C 6 H 3 (CH 3 )(OH) 2 (1 : 2 : 4).

2041 This dihydroxy toluene, which was called lutorcin by
Vogt and Henninger, may be prepared from /3- and 7-amido-
paracresol by the diazo-reaction 1 and by fusing bromoparacresol
with caustic potash. 2

It is readily soluble in water, alcohol, ether and benzene, and
crystallizes in monosymmetric prisms which form characteristic
spherical aggregates and melt at 104 105. Ferric chloride
produces an unstable, greenish blue colouration, and an alkaline
solution becomes coloured red in the air. Like resorcinol it re-
duces silver solution in the cold, is not precipitated by lead
acetate, and gives a precipitate with bromine water which soon
becomes crystalline. On heating with phthalic anhydride and
dissolving the mass in dilute caustic soda, a solution is formed
possessing as fine a green fluorescence as does that obtained by
a similar process from resorcinol. It differs however from the
latter in yielding no colouring matter when 'heated with sul-
phuric acid and nitrobenzene. In presence of ammonia and
moist air it is converted into yellow cresorcein, which dissolves
in dilute caustic soda, forming a blue solution turned red by
acetic acid.

Isordnol. Senhofer obtained this compound by the fusion of
7-toluenedisulphonic acid, 3 and Hakansson prepared a-isorcinol
in a similar manner from a-toluenedisulphonic acid. 4 Claesson
subsequently showed that these two sulphonic acids are identical,
and that, therefore, only one isorcinol can exist. It crystallizes
in needles melting at 87 88, but it resembles cresorcinol
so closely that Neville and Winther look upon the two as
identical, an opinion which is supported by the fact that the
toluenedisulphonic acid has the side chains in the same relation
as cresorcinol.

1 Knecht, Bcr. Dcutsch. Chem. Ges. xv. 298 and 1069 ; Ann. Clicm. Pfiarm.
ccxv. 83 ; Wallach, Bcr. Dcutsch. Chem. Gcs. xv. 2831 ; Neville and Winther,
ibid. xv. 2980. 2 Vogt and Henniuger, ibid. xv. 1081.

3 Ann. Chem. Pharm. clxiv. 131.

4 Bcr. Dcutsch. Chem. Gcs. v. 1084.



C 6 H/CH 3 )(OH) 2 (1 : 2 : 5).

2042 This compound may be obtained from orthotoluidine
just as is quinol from aniline, 1 and may also be prepared from
/3-amido-orthocresol by means of the diazo-reaction. 2 It is
readily soluble in water, alcohol and ether, and crystallizes from
hot benzene or toluene in pointed, rhombic plates which have a
nacreous lustre and melt at 124. Cajustic soda produces a
bluish green colouration which rapidly changes to dark brown ;
bleaching powder solution gives the same reaction, but when
very dilute produces a brownish red colour. Oxidizing agents
readily convert it into toluquinone.

Toluguinol monomethyl e^,C 6 H 3 (CH 3 )(OCH 3 )OH, is formed,
together with the compound described below, by heating tolu-
quinol with caustic soda, methyl iodide and wood-spirit to 190.
It has a faint smell of creosote, crystallizes in plates melting at
72, boils at 240 245, and yields toluquinone on oxidation.

Toluquinol dimethyl ether,- C 6 H 3 (CH 3 )(OCH 3 ) 2 , can easily be
separated from the monomethyl ether, since it is insoluble in
alkalis and non-volatile in steam. It is a liquid which has a
pleasant smell like fennel and boils at 214 218. When
oxidized by chromic acid in acetic acid solution, it is converted
into a compound, C 16 H 16 O 4 , which- is precipitated by water in
brick-red needles and crystallizes from its deep yellow alcoholic
solution, in hair-like needles, which appear almost black when
seen in masses and become silver-grey on- drying. They melt at
153 and sublime when more' strongly heated. Ammonium sul-
phide reduces it to the compound C 18 H 18 O 4 , crystallizing from
alcohol in small prisms, melting, at 173, which are readily

JJiacetotoluquinol, C 6 H 3 (CH 3 )(OCO.CH 3 ) 2 , is formed by the
action of acetyl chloride on toluquinol ; it crystallizes from
alcohol in large tablets melting at 72 (Nietzki).

1 Nietzki, Bcr. Deutsch. Chem. Gcs. x. 834, 19S& ; Ann. Chem. Pharm. ccxv.
a Neville and Winther, Ber. Deutsch. Clicm. Gcs. xv. 2979'.


TOLUQUINONE, C 6 H 3 (CH 3 )O 2 .

2043 This compound is formed when paradiamidotoluene, 1
crude cresol 2 or amidorthocresol 3 is oxidized with manganese
dioxide and dilute sulphuric acid, or when orthotoluidine hydro-
chloride is heated with ferric chloride. 4 It crystallizes in small
golden-yellow plates which readily volatilize, have a penetrating
smell resembling that of benzoquinone, and melt at 69. It
dissolves slightly in cold, more readily in hot water, forming a
golden-yellow solution which is coloured brownish red by alkalis.
Sulphurous acid reduces it to toluquinol.

Dianilidotoluquinone, C 6 H(CH 3 )0 2 (NH.C 6 H 5 ) 2 , is obtained by
the action of aniline on toluquinone in alcoholic solution;
it crystallizes from hot glacial acetic acid in brown, matted
needles, which melt at 232 233 and form a blood-red solution
in sulphuric acid. When boiled with alcohol and sulphuric
acid, anilidoliydrcxytoluquinone, C 6 H(CH 3 )0 2 (NH.C 6 H 5 )OH, is
formed ; it crystallizes from alcohol or acetic acid in deep blue
needles and forms salts with bases.

Dianilidotoluquinone anilide, C 6 H(CH 3 )0(NC 6 H 5 )(NH.C 6 H 5 ) 2 ,
is formed when aniline and toluquinone are brought together in
solution in a mixture of alcohol and acetic acid. It crystallizes
in broad dark-brown plates which have a blue surface lustre,
melt at 167 and combine with acids to form salts, which are only
slightly soluble in water but crystallize well from alcohol.

On heating with alcoholic sulphuric acid, anilido-cthoxytolu-
quinone anilide, C 6 H(CH 3 )0(NC 6 H 5 )(NH.C ? H 5 )OC 2 H 5 ,is formed ;
this compound crystallizes from alcohol in silky, red needles
melting at 115 116, is a tolerably strong base and forms blue
salts. It dissolves in concentrated sulphuric acid with a green
colour. On treatment with alcoholic potash it yields anilido-
hydroxytoluquinone anilide, C 6 H(CH 3 )0(NC 6 H 5 )(NHC 6 H 5 )OH,
crystallizing from hot, dilute acetic acid in brownish needles,
which form a deep green solution in sulphuric acid. It forms
insoluble or difficultly soluble salts with the metals.

Diliydroxytoluquinonc, C C H(CH 3 )0 2 (OHX, is obtained from

1 Nietzki, loc. cit.

"_ Carstanjen, Journ. Prakt. Chvm. [2] xxiii. 425.

3 Nolting and Kohn, Ber. Deutach. Chcm. Gr.s. xvii. 370.

4 Ladenburg, ibid. x. ]l'2f>.



the preceding compound by the action of very dilute caustic potash
solution. It is readily soluble in most solvents and crystallizes
from them badly ; it readily sublimes, however, in brownish
yellow, lustrous plates, melting at 177. Its salts form insoluble
or only slightly soluble precipitates which are not characteristic. 1
Toluquinhydrone, C 6 H 3 (CH 3 )O 2 -(-C 6 H 3 (CH 3 )(OH) 2 , is obtained
by mixing aqueous solutions of the two constituents, and crys-
tallizes in fine, almost black needles which melt at 52 and are
tolerably soluble in water forming a brownish yellow solution


The chlorine substitution products are obtained by treating
orthocresol or metacresol, and therefore also crude cresol, with
potassium chlorate and hydrochloric acid. 2 Trichloroquinone is
likewise formed by this method from orthotoluidineparasulphonic
acid. 3 Sulphurous acid converts them into the corresponding
derivatives of toluquinol.

Dichlorotoluquinone, C 7 H 4 C1 2 2 , yellow transparent tablets.
Trichlorotoluquinone, C 7 H 3 C1 3 O 2 , yellow plate's.

Tetrachlorotoluquinone,C 7 H 2 Cl 4 2 , j ^
Tribromotoluquinone, 4 C 7 tLBr 3 O , yellow plates.


2044 a-Toluquinonoxime, C 6 H 3 (CH 3 )O(NOH). This compound
which is generally known as nitroso-orthocresol, is formed in an
analogous manner to quinonoxime (Part III. p 295) by the action
of nitrosyl sulphate on an aqueous solution of orthocresol, 5 or
by adding hydroxylamine hydrochloride to a dilute solution of
toluquinone. 6 It is only slightly soluble in cold, more readily in hot

* Hagen and Zincke, Bcr. Deutsch. Chem. Ges. xvi. 1558.

bouthworth, Ann. Chem. Pharm. clxviii. 274 ; Bergmann, Hid. clii. 243 ;
Brauninger ibid, clxxxv. 352 ; Knapp and Schultz, ibid. ccx. 176.
' Hayduck, ibid, clxxii. 209.

* Canzpneri and Spica, Bcr. Deutsch. Chem. Ges. xvi. 793.
; Bolting and Kohn, ibid. xvii. 370.

6 Goldschmidt and Schmidt, ibid. xvii. 2063.


water, from which it crystallizes in long, white needles, melting
at 134 135. It forms a reddish brown solution in dilute
alkalis, and is thrown down by acids as a white, flocculent

Potassium a-toluquinonoximate, C 6 H 3 (CH 3 )O(NOK), is ob-
tained by the addition of an ethereal solution of toluquinone-
oxime to a solution of potassium ethylate, as a yellowish
green precipitate, which crystallizes from acetone in brown

Sodium a-toluquinonoximate, C 6 H 3 (CH 3 )0(NONa) + 3H 2 O, is
a dark green precipitate which crystallizes from acetone in short,
brown needles, and forms a reddish brown solution in water ; it
detonates when heated.

Toluquinonoxime gives Liebermann's reaction with phenol
and sulphuric acid ; potassium ferricyanide oxidizes it to
/3-nitro-orthocresol, and nitric acid to dinitro-orthocresol, while it
is converted into 5-amido-orthocresol by reduction.

a-Toluquinonc chlorimide, C 6 H 3 (CH 3 )O(NC1), is formed in an
analogous manner to quinone chlorimide when a concentrated
solution of bleaching powder is added to a dilute hydrochloric acid
solution of y-amido-orthocresol ; the liquid first becomes coloured
cherry-red, changing to golden-yellow, the chlorimide then
separating out. It crystallizes from benzene in yellow needles,
which melt at 87 88 and detonate at higher temperatures.
When boiled with water it volatilizes, a portion being simul-
taneously decomposed into a-toluquinone and brown, amorphous
bodies ; it also gives Liebermann's reaction. 1

J3- Toluquinonoxime, or Nitrosometacrcsol, C 6 H 3 (CH 3 )O(NOH),
has been prepared by boiling nitrosodimethylmetatoluidine ; it
is slightly soluble in hot water, from which it crystallizes in
small, colourless needles, while it is deposited from solution in
ether or acetic acid in thick needles or prisms, decomposing at
140 150.

/3-Toluquinonoxime acetate, C 6 H 3 (CH 3 )O(NO.C 2 H 3 O), is ob-
tained by the action of acetic anhydride on the compound
just described ; it crystallizes from alcohol in prisms melting at

/3-Toluquinonoxime gives Liebermann's reaction in a most
characteristic manner ; nitric acid oxidizes it to trinitrometa-

ITOSol. 2

1 Hirsch, Ber. Deutsch. Chem. Ge*. xviii. 1514.

- Wur.-it.'i-ainl Ricdel, ibid. x:i. 1799.


The following formulas explain the isomerism of the two
toluquinonoximes :





v \/

c c

ii 1


Paracresol does not form a nitroso-compound or quinonoxime,
since the methyl group is situated in the para-position.

Hydroxytoluquinonoxime, C 6 H 2 (CH 3 )(OH)O(NOH). This
compound, which is also called nitroso-orcinol, is obtained by
evaporating a solution of 12 grammes of orcinol and 4 grammes
of caustic soda to a syrup, and gradually adding 12 grammes
of amyl nitrite to the cold mass with constant stirring; the
mixture is then gently heated on the water-bath until a small
portion dissolved in water gives a red precipitate with sulphuric
acid. The fused mass is then dissolved in water and precipitated
with dilute sulphuric acid. Nitroso-orcinol crystallizes from alcohol
in small dark red prisms, which become coloured black at 110
without melting. 1 It has the following constitution :





Azo-ordn, C 14 H U N0 3 . Weselsky obtained this compound by
the action of his reagent on an ethereal solution of orcinol ; 2 it is
also formed when orcinol is heated on the water-bath with nitroso-
orcinol and sulphuric acid (Brunner and Kramer). It crystal-
lizes in small, brownish red prisms which dissolve in alkalis
forming a deep purple-coloured solution with a splendid orange-

* Dn adK mer ' Bcr - D tsch. Chem. Ges. xvii. 1879.


red fluorescence; acids precipitate it from this as a scarlet

Its formation is quite analogous to that of azoresorcin,
C 10 H 9 NO 4 , but it is not homologous with this substance. The
homologous compound is, however, first formed and is converted
into azo-orcin with loss of water; the latter compound may
possibly possess the following constitution :


CH 3 .C 6 H 3 < >NC 6 H 2 (CH 3 )( >C 6 H 2 (CH 3 )N<( >C 6 H 3 CH 3 .

Liebermann obtained a similar colouring matter by gradually
adding 40 grammes of his reagent to a solution of 10 grammes
of orcinol in 10 grammes of sulphuric acid. 1 Another colouring
matter is simultaneously formed but can easily be separated, as
it forms a sodium salt which is insoluble in alcohol, while that
of the former forms a purple-red solution with a cinnabar-red
fluorescence. The colouring matter, C 29 H 21 NO 6 , separated from
this solution by the addition of an acid, is an amorphous mass
with a beetle-green fluorescence, the aqueous alkaline solution of
which has a brownish red fluorescence. The formation of this
compound corresponds exactly to that of Liebermann's phenol
colouring-matter, and its constitution is therefore the following :


HO^ X O.C 6 H 3 -CH 3

HOV ^O.CeH, CH 3


The second colouring matter, C. 22 H 21 N0 7 , is an oxidation
product of the former, which it resembles very closely; its violet
alkaline solution, however, does not fluoresce (Brunner and


2045 Mcthylpyrogallol, or Methylpyrogallic acid, is the only
known compound of this group. Its dimethyl ether occurs,
together with the same ethers of pyrogallol and propylpyrogallcl
1 Her. Deutsch. Chem. Ges. vii. 1110.


in the fraction of beech-wood-tar creosote which dissolves in
alkalis and boils at between 255 and 270. In order to
separate them, the mixture is heated with benzoyl chloride, the
benzoic ethers separated by fractional crystallization and then
decomposed by alcoholic potash.

Mdhylpyrogallol dimethyl ether, C r H 2 (CH 3 )(OCH,) 2 OH, is a
crystalline substance, melts at 36, and boils at 265. On heating
with concentrated hydrochloric acid, methylpyrogallol is obtained ;
this closely resembles pyrogallol, and on heating sublimes in
needles, which melt at 129. Its aqueous solution is coloured
brown by ferrous sulphate, and its alkaline solution rapidly turns
brown in the air. 1



2046 The history of these compounds goes hand in hand
with that of the nitrotoluenes. Hofmann and Muspratt reduced
crude nitrotoluene by repeated treatment with alcoholic am-
monium sulphide and obtained the product free from unaltered
nitrotoluene by washing well with water, treating with hydro-
chloric acid and distilling the liquid, after the removal of all
alcohol by evaporation, with caustic soda ; they thus obtained an

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