November 18,1871.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
415 
lure is raised, as may be seen from the following 
figures:— 
At 212° 100 parts of water dissolve .... "034 
At 400° 100 parts of water dissolve .... ’820 
At 480° 100 parts of water dissolve .... 3'160 
Alizarine is freely soluble in alcohol, ether, wood spirit, 
benzole, turpentine, sulphuret of carbon, and glycerine. 
It is soluble without decomposition in sulphuric acid, 
even at a temperature of 400° F., and is thrown down 
unchanged when large quantities of water are added. 
It is soluble in a warm solution of alum, but insoluble in 
■a cold one. It has been assigned different formula! by 
different chemists, the two most generally adopted being 
that of Dr. Schunck, C 14 H 10 O 4 , and that of Wolf and 
Strecker, C 20 H 12 O G . Alizarine gives a purple colour 
with a weak solution of caustic alkali, which undergoes 
no change by the action of air. It yields, with alumina 
fixed in fabrics, a variety of red and pink shades; with 
•oxide of iron it gives purples and blacks; and, with a 
mixture of these two oxides, chocolates. 
I shall now call your attention to one of the most 
interesting and important discoveries of chemistry, as 
.applied to manufactures, which have been made of late 
years, namely, the artificial production of this most impor¬ 
tant colour-giving principle, alizarine, or of a substance 
which, if not identical with, has great similarity to it. 
Messrs. Graebe and Liebermann, and Mr. Perkins, believe 
in the identity of the artificial product with the natural 
one. But this is denied by M. Alfraise, on the grounds, 
first, that the formula given by Messrs. Graebe and 
Liebermann does not agree with that given by Dr. 
.Schunck, as is shown by the following figures:— 
Schunck. Graebe and Liebermann. 
ChUiqO.! C h H 8 0 4 
Secondly, that the artificial alizarine does not give the 
.same coloured sublimate as the natural alizarine; and 
thirdly, that if both these substances are acted on by 
nitric acid, natural alizarine is converted into phthalic 
acid, whilst the artificial alizarine, which he calls aliza- 
purine, yields a large quantity of a nitro-compound 
having an intensely bitter taste, mixed with only a mere 
trace of phthalic acid. These observations of M. Alfraise 
have been confirmed by M. Ivopp. That the commercial 
artificial alizarine is not identical with a natural aliza¬ 
rine is rendered still more certain by the researches of 
Dr. Schunck, who, on examining a sample obtained from 
Mr. Perkins, found it to contain a large quantity of a 
compound crystallizing in yellow, silky needles, anthra- 
flavic acid, and which he obtained by treating Mr. 
Perkins’s product with alcohol. On treating the acid 
with fuming nitric acid he obtained a nitro-compound, 
the potash salt of which he describes as resembling 
picrate of potash. This is doubtless the bitter principle 
which Alfraise obtained, but did not study. Dr. Schunck 
gives the formula of anthrafiavic acid as C 15 H 12 0 4 , and 
considers it homologous to alizarine, one equivalent of 
its hydrogen being replaced by methyl. Messrs. Graebe 
and Liebermann, and Mr. Perkins, found their opinion 
.as to the identity of the two alizarines, on the fact that 
they give the same absorption bands on being submitted 
to Professor Stokes’s spectrum test. 
Artificial alizarine was first made, in 1869, by Messrs. 
Graebe and Liebermann. The substance from which 
they obtain it is Anthracene , a body discovered by Pro¬ 
fessor Anderson, of Glasgow. Anthracene is one of the 
last products passing over in the dry distillation of coal- 
tar, and is found most abundantly in the 10 or 15 per 
cent, which comes over from the temperature where soft 
pitch is formed, and that where hard pitch is produced. 
The quantity of anthracene in coal-tar varies greatly; it 
is most abundant in the tars obtained from those coals 
which yield most naphtha. The South Staffordshire 
coals give the largest quantity, whilst the Newcastle 
coals give very little. Its extraction can only be carried 
«on with advantage in cold weather, as it becomes very 
soluble on a slight rise of temperature in the oily homo- 
logues which accompany it. At a temperature of about 
40°, the distillate above described is semi-fluid; it is placed 
in a hydro-extractor, and the oily fluid separates from 
the solid matter, which is then submitted to cold and hot 
pressure. The cake thus formed is pulverized and care¬ 
fully washed with petroleum spirit, having a boiling- 
point of about 180°, wdiich leaves anthracene moderately 
pure. This pow r der dissolved in alcohol and crystallized, 
yields anthracene in nearly white scaly crystals, or in a 
fit state for the manufacture of artificial alizarine. 
Messrs. Graebe and Liebermann oxidized the anthra¬ 
cene (C 14 H 10 ), by nitric acid, into anthrachinon (C 14 H 8 0 2 ), 
this being again converted into bibrom anthrachinon 
(C 14 H G Br 2 0 2 ), winch by fusion with potash is changed 
into alizarine (C 14 H 8 0 4 ). There are three patents pub¬ 
lished, and a process, the details of which are kept secret. 
It is curious to notice that the patent taken out by the 
above-named gentlemen and Mr. Caro is dated the 25th 
of June, 1870, while Mr. Perkins entered his on the day 
following, in wliich nearly the same processes are de¬ 
scribed, merely employing different oxidizing agents. 
The following is an outline of one of the processes de¬ 
tailed in the specification of Messrs. Caro, Graebe and 
Liebermann:—One part of anthracene is heated with 
four of sulphuric acid, of sp. gr. T845, for three or four 
hours, to a temperature of 212° F., and then for an hour 
at 300°. The mixture is allowed to cool, and to it is 
added water equal to three times the weight of anthra¬ 
cene taken, and manganese equal to four times that 
weight. The whole is boiled for three hours, and milk 
of lime is then added, wliich gives rise to a deposit con¬ 
sisting of the excess of lime and manganese used, and 
protoxide of manganese, while there remains in solution 
a double sulphate of anthrachinon and lime. This solu¬ 
tion is now acted on by carbonate of soda in slight ex¬ 
cess, carbonate of lime separates, and the salt of soda thus 
produced is evaporated to dryness. To this solid mass 
are then added two or three parts of caustic potash or soda 
and a small quantity of water, and the whole heated 
under pressure, in suitable vessels, at a temperature of 
35U° to 500° for one hour, wlien the anthrachinon is 
further oxidized and converted into alizarine. Thus an¬ 
thracene, C 14 H 10 , gives anthrachinon, C 14 H 8 0 2 , and this 
alizarine, C 14 H 8 0 4 . The alkaline mass, on cooling, is 
dissolved in w r ater, and sulphuric or acetic acid added in 
slight excess, wlien an orange-y ello w flocculent substance 
precipitates, which, wlien properly washed and dried, is 
artificial alizarine. 
The second colour-giving principle of madder, to which 
I have referred several times already, is called purpurine, 
and was also discovered by MM. Robiquet and. Colin, in 
1828. Although in commerce it is sold as a red powder, 
as has been mentioned above, still, by heating at a 
temperature of 480° F., it can be obtained in the form of 
feathery crystals, of an orange-red colour. It is more 
soluble in water than alizarine, especially at a tempera¬ 
ture of 140° F., and is also soluble in the menstrua already 
mentioned under alizarine. Further, it gives, a red 
colour with caustic alkali, instead of purple as alizarine. 
It is soluble in a cold solution of alum, while alizarine is 
not. When fixed on fabrics, its colours.do not stand ex¬ 
posure to light as well as those of alizarine. 
Professor Stokes, of Cambridge, has found a most 
elegant method of discovering and characterizing, mere 
traces of these colouring principles. So delicate, is the 
test, that the colouring matter on one square inch of 
dyed fabric is sufficient to obtain the results. He treats 
the fabric with a solution of carbonate of soda, which 
dissolves the colouring matter. The solution is then in¬ 
troduced into a small tube, which is placed before a slit 
in the shutter of a dark room. The light which passes 
through is decomposed by a prism, wlien a spectrum is 
produced. The operator will observe that, wlien l' ur P^' 
rine is taken, there are principally two black bands 
formed by the absorption of light in the green pait ot 
