Lapachol.(CHAPTER II. The Naphthoquinone Group.) (Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

This colouring matter has been obtained from the wood of the Lapacho tree, from Greenheart wood, and also from Bethaberra wood. It was from the first-named that Arnaudon (Comptes rend., 1858, 46, 1154) originally obtained it by extracting the wood with alcohol, and recrystallising the product from a mixture of alcohol and ether. Stein (J. f. pr. Chem., 99, 1) showed that the same colouring matter was present in Greenheart wood, whilst Green and Hooker (Amer. Chem. Jour., 11, 267) obtained it from Bethaberra wood.

According to Paternò (Gazetta, 12, 337; 21, 374) the colouring matter is best extracted from the wood by means of soda solution (1 gram soda crystals in 16 grams water for 20 grams finely divided wood), the product being precipitated from the combined extracts by means of hydrochloric acid, purified by extraction with barium hydroxide solution and reprecipitation with acid. The product thus obtained when recrystallised from benzene is readily obtained in a pure condition.

Kermes(CHAPTER I. The Anthraquinone Group.)(Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Kermes is the most ancient dyestuff on record, for it was known in the time of Moses, and is mentioned in Scripture by its Hebrew name, "tola" or "tolaschani". According to Tychsen (Bancroft's "Philosophy of Permanent Colours," i, 394), "the scarlet or kermes dye was known in the East in the earliest ages before Moses, and was a discovery of Phoenicians in Palestine, but certainly not of the small wandering Hebrew tribes". Under the name "coccus" it is frequently referred to by the Greek and Latin writers.

Kermes is an insect found on the oak kermes (Quercus coccifera, Linn.), and when living the female insects, which are fixed to the twigs of the tree, resemble bluish berries, and are covered with a whitish powder. As soon as their eggs are on the point of hatching these insects should be collected, killed by exposure to the steam of vinegar, and dried, and the product has then the appearance of pale reddish-brown grains. According to Bancroft, it would require 10 or 12 lbs. of kermes to produce the effect of a single lb. of cochineal.

Kermesic acid, C₁₈H₁₂O₉, the colouring matter of kermes, was first isolated, in the crystalline condition, by Heisse (Arbeit, a. d. K. Gesundheitsamte, 1895, 513), and has since been examined by Dimroth (Ber., 1910, 43, 1387; and Annalen, 1913, 399, 43). To isolate the kermesic acid, the kermes is first extracted with ether to remove wax, and this has been examined by Dimroth and Sherndal (Annalen, 1913, 399, 43), and identified as ceryl cerotate, C₅₂H₁₀₄O₂. The residue is then allowed to stand overnight with an ethereal solution of hydrochloric acid, by which means the kermesic acid, which exists in kermes in the form of a salt, is liberated and made capable of removal by repeated extraction with ether. For the purification of the substance, it is converted into its sparingly soluble sodium salt, which allows of its separation from flavo-kermesic acid, a substance stated by Dimroth to be present in kermes dye to the extent of about 0.06 per cent. the sodium salt of this being soluble in hot 2N sodium acetate solution, whereas the disodium salt of kermesic acid is almost insoluble. The sodium salt when dissolved in boiling sodium hydroxide solution and treated, whilst boiling, with excess of hydrochloric acid, yields a crystalline precipitate of kermesic acid.

---

Kermesic acid is thus closely related to carminic acid, which is also considered by Dimroth to be a derivative of anthraquinone.

Dyeing Properties.

According to Hellot (Bancroft, "Philosophy of Permanent Colours," i, 404), "the red draperies of the figures exhibited in the ancient Brussels and other Flemish tapestries were all dyed with kermes". "The fine red or crimson colour of these tapestries, which was originally called simply scarlet, took the name of Venetian scarlet, after the cochineal scarlet upon a tin base was discovered...."

For the production of this scarlet, the wool, previous to dyeing, was mordanted with alum and tartar; and, according to Bancroft, there is no evidence even in more recent years of the employment of a tin mordant in respect of this colouring matter, although the experiments he carried out indicated that by this latter method a scarlet could be produced "in every respect as beautiful and estimable as any which can be dyed with cochineal".

Lac Dye(CHAPTER I. The Anthraquinone Group.)(Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Lac dye is produced by an insect, the Coccus lacca or ficus, living on the twigs of various kinds of trees, particularly the Ficus religiosa (Linn.), the Zizyphus jujuba (Lam.), and the Butea frondosa (Roxb.). These insects appear usually in November, and subsequently fasten themselves to the fleshy portions of the young branches. Gradually the abdomen of the insects becomes covered by a viscous fluid, which slowly forms a cellule surrounding the animal. The substance composing this cellule is the stick lac. The cellule attains its full size in March, and the insect then exhibits the appearance of a red oval- shaped, smoothly polished lifeless sack entirely filled with a beautiful red liquid; its size is then the same as that of the fully grown cochineal (Crookes, "Dyeing and CalicoPrinting," p. 354). Commercial stick lac is chiefly gathered on the hilly banks of the Ganges in India, that for dyeing purposes possessing a deep red colour, whereas the pale perforated kind in which no insects exist is employed for varnish-making, and constitutes the material for shellac.

Of lac, the following varieties occur: stick lac, the crude product together with the twigs upon which it is formed: grained lac, the material removed from the twigs; and caked lac, the latter variety fused and cast into moulds.

Such a resinous material is not suitable for dyeing purposes, and a simple process is adopted to remove the colouring matter from the resin, or at least to obtain it in a more concentrated form. This consists in extracting the stick lac with hot dilute sodium carbonate solution, evaporating the extract, and moulding the residue into square cakes. According to Crookes (loc. cit.) the product, which is lac dye, contains on an average about 50 per cent, of colouring matter, 25 per cent, of resin, and 22 per cent, of earthy impurities.

Lac dye is an extremely ancient dyestuff, and was employed in the East for many centuries before it was known in Europe. It appears to have been introduced into this country about 1790. Early in the last century, lac dye was a very important article of commerce, so much so that at one time shellac was practically a bye-product of its manufacture. The position of these products has now been reversed, for whereas the dyestuff is almost defunct, the shellac industry is of considerable importance.

According to the older writers, the colouring matter of lac dye was considered to be identical with that of cochineal, but that this is not the case has been clearly indicated by Schmidt (Ber., 20, 1285).

---

Dyeing Properties.

The dyeing properties of lac dye are practically identical with those of cochineal, but the shades obtained are somewhat faster. Owing to the resinous and mineral impurities accompanying the colouring matter, it is not readily soluble in water, and before use it is therefore ground to a paste with the requisite quantity of tin spirit together with a little hydrochloric acid, and allowed to stand overnight. Cochineal and lac dye can be used together with advantage, or after the wool is dyed with lac it may be entered into a fresh bath with cochineal. Its employment at the present time is, however, extremely limited.

Fowler (Indian Textile Jour., 1917, 244) has made attempts to standardise various Indian colouring matters so that they may be marketed in uniform strengths. It would appear that "Lac dye" is one of those with which he has been concerned.

Cochineal. Dyeing Properties of Cochineal.(CHAPTER I. The Anthraquinone Group.)(Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Cochineal has been little employed in cotton dyeing, but was very largely used in silk and wool dyeing. It has now been practically replaced by the azo-scarlets.

Two shades of red are obtained upon wool with cochineal, namely, crimson, which is produced by means of aluminium sulphate, and a very fiery scarlet, for which stannous and sometimes stannic chlorides are employed.

For crimson, wool is mordanted with aluminium sulphate and tartar, and is then dyed in a separate bath with cochineal. The employment of calcium salts in the dyeing operation is not beneficial. Fairly good shades of crimson can also be obtained by mordanting and dyeing in a single bath with aluminium sulphate, oxalic acid, and cochineal. For scarlet, wool can be mordanted with stannous chloride and tartar, and dyed in a separate bath with cochineal. A single-bath method, employing stannous chloride, oxalic acid, and cochineal, has, however, been very largely used for this purpose. On the other hand, preparations of stannic chloride, known as "tin spirits," "scarlet spirits," and "nitrate of tin," are and have been much employed by dyers of cochineal scarlet. Though, when used alone, stannic chloride does not give such brilliant shades as the stannous mordant, a mixture of both is considered to be beneficial. For very yellow shades of scarlet, yellow colouring matters can be added to the cochineal dye-bath, and of these "flavine" has been considerably employed.

Cochineal red on wool possesses considerable fastness to light, but has the defect that weak alkalis and soap cause it to acquire a duller or more bluish shade.

Wool mordanted with potassium dichromate gives with cochineal a good purple colour, whereas with ferrous sulphate and tartar, purplish, slate, or lilac colours can be produced. These mordants, however, are not employed in practice. A good crimson shade is produced by mordanting silk with alum, and dyeing with an extract of cochineal. In scarlet dyeing, silk is preferably first dyed yellow, then mordanted with "nitromuriate of tin," and finally dyed in a second bath with the assistance of cream of tartar. Silk can also be dyed in a single bath with cochineal, stannous chloride, and oxalic acid.

Cochineal. Technical Preparations of Cochineal.(CHAPTER I. The Anthraquinone Group.)(Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Ammoniacal Cochineal.

When a solution of carminic acid in ammonia is allowed to stand for some time, there is formed a new compound, which appears to consist of carminic acid in which one of the hydroxyls has been replaced by an amino group. The formula assigned to this substance by Schützenberger was C₉H₉NO₄. This reaction, long known, has been utilised for the production of a new colouring matter termed ammoniacal cochineal, or carminamide, and this comes into commerce either as cakes or in the form of a paste.

The first variety is usually prepared by allowing one part of cochineal to stand in a closed vessel for three months with three parts of ammonia. The clear liquid is decanted, treated with about half its weight of gelatinous alumina, evaporated, and when the mass has become thick, it is cut up into cakes and dried.

The paste is manufactured in a somewhat similar manner, the ammonia, however, being only allowed to react for eight days. The clear liquid is then evaporated to about one-third its bulk without addition of alumina (Crookes, "Dyeing and Calico Printing ").

Ammoniacal cochineal dyes much bluer shades than cochineal itself, and it is sometimes employed in conjunction with the latter. Its use is now very limited, but it finds some application in the blueing of bleached cotton.

Cochineal. The Constitution of Carminic Acid.(CHAPTER I. The Anthraquinone Group.)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Nitrococcussic acid was obtained by W. de la Rue from carminic acid by the prolonged action of boiling nitric acid. It was subsequently studied by v. Kostanecki and Niementowski (Ber., 18, 250), and was found to be identical with the trinitrocresotinic acid, of the following constitution: [KUVA PUUTTUU]

When carminic acid dissolved in 50 per cent, acetic acid is treated with an excess of bromine, and the solution digested at the boiling heat, two substances, known as α- and β-bromcarmines, are produced (Will and Leymann, Ber., 18, 3180).

α-Bromcarmine, C₁₀H₄Br₄O₃, the more sparingly soluble substance, crystallises in colourless needles, and melts at 247-248°, with decomposition. When oxidised with potassium permanganate in alkaline solution, it gives dibrommethylhydroxyaldehydrobenzoic acid and dibrommethylhydroxyphthalic anhydride.

On treatment with hot caustic soda solution, a-bromcarmine yields, in addition to a purple-red colouring matter, dibrommethylhydroxyphthalic acid, and bromoform (Miller and Rohde). As a result of this reaction, these authors assigned to α-bromcarmine the constitution of a methylhydroxytetrabromdiketohydrindene for Zincke (Ber., 20, 3227; 21, 2388) had previously shown that dibromdiketohydrindene itself under similar treatment yields both phthalic acid and bromoform.

β-Bromcarmine, C₁₁H₅Br₃O₄, is obtained as a yellow amorphous powder, easily soluble in alcohol (Will and Leymann), and is best purified by means of its potassium salt. Crystallised from acetone, it separates in orange needles, melting at 232° (Will and Leymann) or 288° (Miller and Rohde). By the action of bromine in the presence of 50 per cent, acetic acid solution, it is converted into abromcarmine. As a result of their investigation, Miller and Rohde ascribed to β-bromcarrnine the constitution of a methyldihydroxytribrom-a-naphthaquinone, possessing one of the following formulæ: [KUVA PUUTTUU]

This suggestion was supported by the fact that bromoxynaphthaquinone, on treatment with bromine and caustic soda solution, is converted into dibromdiketohydrindene (Zincke, loc, cit.)

Additional support for this view was obtained by a study of the behaviour of β-bromcarmine with zinc-dust in alcoholic solution. Thus the acetyl compound of the reduction product, melting-point 206°, gave, on analysis, numbers agreeing with those of the acetyl derivative of a methyldibromdihydroxynaphthahydroquinone, possessing the following formula: [KUVA PUUTTUU]

From a consideration of the points above enumerated, Miller and Rohde considered that the constitution of carminic acid could be represented by one or other of the following expressions: [KUVA PUUTTUU]

As, however, such formulæ require C = 64.7 per cent., H = 3.92 per cent., figures which are much higher than those given by the analysis of carminic acid itself, these authors suggested the addition of two molecules of water of hydration, as shown below: [KUVA PUUTTUU]

A substance of this constitution would require C = 55 per cent., and H = 5 per cent.

Somewhat later, Liebermann and Voswinkel (Ber., 30, 688) studied the oxidation of carminic acid with alkaline potassium permanganate at the ordinary temperature, and in this way succeeded in producing two important acids.

Cochenillic acid, C₁₀H₈O₇, crystallises in colourless needles, which melt at 224-225° with evolution of CO₂. It is tribasic, and at 260° is converted into hydroxymethylphthalic anhydride. When heated with water in a sealed tube at 210° it yields symmetrical cresotinic acid and in the same manner at a lower temperature, 170°, gives α-coccinic acid or m-hydroxyuvitic acid. The constitution of cochenillic acid is therefore as follows: [KUVA PUUTTUU]

α-Coccinic acid, C₉H₈O₅, the second product of the oxidation, which, as already indicated, can also be prepared from cochenillic acid, proved to be identical with the hydroxyuvitinic acid of Oppenheim and Pfaff (Ber., 7, 929). It consists of colourless needles, melting-point 239°.

Liebermann (ibid., 30, 1731), whilst agreeing with the diketohydrindene constitution which had been assigned to a-bromcarmine by Miller and Rohde, considered that β-bromcarmine was an indone rather than a naphthoquinone derivative, and could be better represented as follows: [KUVA PUUTTUU]

It was probable, indeed, that carminic acid itself was a hydrindene or bishydrindene derivative, and the following constitutions were at the time suggested for it: [KUVA PUUTTUU]

In a subsequent paper, however, Liebermann and Voswinkel (Ber., 37, 3344) consider that carminic acid is possibly a tetrahydrate of α-dimethyldihydroxynaphthacenequinonedicarboxylic acid and it was observed that the dimethyltetrahydroxynaphthacenequinone prepared by these authors not only possessed weak tinctorial property of a cochineal-like character, but in several respects closely resembled carminic acid itself.

Rohde and Dorfmuller (Ber., 1910, 33, 1363) further examined β-bromo-carmine, and obtained results which support the naphthoquinone constitution assigned to it by Miller and Rohde (loc. cit.), but disprove Liebermann's contention that it is a derivative of indone. By reduction with zinc-dust and acetic acid and subsequent acetylation, β-bromo-carmine gives the compound C₁₇H₁₄O₈Br₂ colourless needles, melting-point 208°C.

Simultaneous hydrolysis and oxidation converts this into the substance [KUVA PUUTTUU] orange prisms, melting-point 258°C.; and it thus appears that by the latter treatment an hydroxyl has entered the quinone nucleus. The diacetyl derivative melts at 233°C. When distilled with zinc-dust, this product, and also β-bromo-carmine itself, give naphthalene.

A valuable contribution to the subject was made by Dimroth (Ber., 1909, 42, 1611), who studied the oxidation of carminic acid with potassium permanganate at 0° in presence of sulphuric acid. The solution thus obtained gave nothing to ether, but on heating for three-quarters of an hour at 90°, it evolved carbon dioxide, and ether then extracted carminazarin.

Carminazarin crystallises from water in garnet-red needles, decomposing at 240-250°. It possesses the constitution, and is very similar to isonaphthazarin.

Its alkaline solution when treated with a stream of oxygen, is quickly decolorised with formation of 5:6-dicarboxy-4-hydroxy-o-tolylglyoxylic acid.

A further point of resemblance of carminazarine to isonaphthazarine is shown by its behaviour with nitric acid in glacial acetic acid, for whereas the latter gives tetraketotetrahydronapthalene, the former yields the analogous Carminazarinquinone crystallising in colourless prisms and which, when heated with water or acetic acid, passes back to carminazarin.

The intermediate product formed by the oxidation of carminic acid with permanganate at 0° insoluble in ether, and which, on heating, is transformed into carminazarin, is termed by Dimroth carminoquinone. The constitutions assigned to this substance and tentatively to carminic acid are given below: [KUVA PUUTTUU]

Carminic acid was, therefore, not a symmetrical compound, and the nature of the group C₁₀H₁₅O₇ was not then determined. At the time, Dimroth considered that the coccinin (see above) of Hlasiwetz and Grabowski, and which is prepared by fusing carminic acid with potassium hydrate, had probably the constitution of a tetrahydroxymethylnaphthalene.

Later, Dimroth (Annalen, 1913, 399, 1) re-examined this product in detail, preparing it by fusing carminic acid with caustic potash at 170-200°C. To it he gave the formula C₁₇H₁₄O₆, and described the pale yellow crystalline tetra-acetyl derivative, C₁₇H₁₀O₆(CH₃CO)₄, melting-point 242-244°C.

When coccinin was oxidised by means of air, or oxygen, in alkaline solution (6 per cent. NaOH), the colour changes above described occurred, and when the pure violet colour had been obtained, acidification with hydrochloric acid yielded a substance coccinone, C₁₇H₁₂O₇, which forms dark brown glistening crystals and decomposes at 250°C.; it yields a tri-acetyl derivative,
C₁₇H₉O₇(CH₃CO)₃,
orange-red crystals, melting-point 210°C., and also ferms three different barium salts (one of which has a composition analogous to the sodium hydrogen salt of 2:6-dihydroxy-8-methyl-a-naphthoquinone-3:5-dicarboxylic acid). Coccinone is reconverted into coccinin by reduction with zinc-dust and ammonia; on the other hand, alkaline oxidation by means of hydrogen peroxide below 20°C. gives rise to two products, cochenillic acid, and an unexamined acid.

Dimroth now formed the opinion that coccinin and coccinone are derivatives of anthranol and anthraquinone respectively, and the position of one of the hydroxy, methyl, and carboxyl groups in coccinone is made clear by the production from it of cochenillic acid. To coccinone Dimroth ascribes the structure [EI KUVAA] and to coccinin either the structure [EI KUVAA].

When heated with water at 200° or dilute sulphuric acid at 170°C. coccinone loses carbon dioxide, yielding decarboxy-coccinone, to which the structure [EI KUVAA] is given; it forms red-brown crystals, and dissolves in alkalis to form purple-red solutions, and in concentrated sulphuric acid with a blue colour which becomes violet on addition of boric acid.

Not only coccinin, but carminic acid itself, has been further examined by Dimroth (loc. cit.), and as a result he considers that this substance is also a derivative of anthraquinone. He has oxidised carminic acid by means of hydrogen peroxide in aqueous caustic soda, using cobalt sulphate as catalyst, and in this way obtained in the first instance carminoquinone, but the reaction proceeded further with the formation, after acidification with 80 per cent, acetic acid, of a yellow crystalline compound, C₂₆H₁₃O₁₆Na₃, 5H₂O, which, when triturated at 0°C. with dilute hydrochloric acid, yielded 2:6-dihydroxy-8-methyl-a-naphthoquinone-3:5-dicarboxylic acid: pale yellow, hygroscopic crystals - trisodium salt, C₁₃H₅O₈Na₃,4H₂O, orange needles.

The orientation of this acid has been established by Dimroth by comparison of its colour reactions with those of 2:6-dihydroxy-α-naphthoquinone, synthetically prepared by Dimroth and Kerkovius, as also by its conversion into carminazarin by treatment with acid permanganate. Moreover, the structure previously assigned by Dimroth to carminazarin, viz. 2:3:6-trihydroxy-8-methyl-α-naphthoquinone-5-carboxylic acid, has been supported by conversion of carminazarin-quinone the oxidation product of carminazarin into a diphenazin, C₂₄H₁₄O₃N₄, by treatment with an alcoholic solution of ο-phenylene-diamine. The product crystallises in yellow needles, and yields an acetyl derivative, C₂₆H₁₆O₄N₄.

When 2:6-dihydroxy-8-methyl-α-naphthoquinone-3:5-dicarboxylic acid the oxidation product of carminic acid referred to above is warmed with water, carbon-dioxide is eliminated with the production of 2:6-dihydroxy-8-methyl-α-naphthoquinone-5-carboxylic acid: brown-yellow needles, potassium salt, C₁₂H₇O₆K, lemon-yellow crystals; dipotassium derivative, C₁₂H₆O₆K₂, orange-red crystals.

This compound when brominated in glacial acetic acid at 40° yields a monobrom derivative, yellow needles, melting-point 240-244°, which on treatment with hydrobromic acid yields α-bromo-carmin, whilst with bromine in cold methyl alcohol, the product is β-bromocarmin (Will and Leymann), which proves that this body has the structure [KUVA PUUTTUU] assigned to it by Miller and Rohde.

Beyond the above-mentioned decomposition products of carminic acid, Dimroth has obtained a 5 per cent, yield of hydrocarbons of the anthracene series by distillation with zinc-dust in an atmosphere of hydrogen. After oxidation of the mixture of hydrocarbons he isolated anthraquinone, and possibly α-methyl-anthraquinone.

By treatment of carminic acid with boiling dilute sulphuric acid, Dimroth has also obtained a 10 per cent, yield of trihydroxy-methylanthraquinone carboxylic acid (C₁₆H₁₀O₇), needles, melting-point above 300°, and this acid when heated with water at 230-240°, passes into trihydroxy-methyl-anthraquinone by loss of carbon dioxide.

Dimroth considered the possibility that the anthraquinone nucleus is produced during the reactions described above, but concluded that this is not the case, and that it is present as such both in carminic acid and coccinin. Dimroth formulates carminic acid thus [KUVA PUUTTUU]

On the other hand, C. and H. Liebermann (Ber., 1914, 47, 1213) bring forward arguments, chiefly the smallness of the yield of anthraquinone or anthracene derivatives obtained by Dimroth, in favour of the view that the anthracene nucleus is formed during the degradation reactions.

These authors have also re-examined the "ruficoccin" of Liebermann and van Dorp (see above), and conclude that it consists of a mixture of trihydroxy-methyl-anthraquinone carboxylic acid, and trihydroxy-methyl-anthraquinone, which is confirmation of the work of Dimroth, Incidentally they described carminic anhydride, C₂₂H₂₀O₁₂, prepared by heating carminic acid with thionyl chloride vivid red powder, resembling carminic acid, though less soluble. It is reconverted into the latter by the action of aqueous alkalis.

Cochineal(CHAPTER I. The Anthraquinone Group.)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

This important natural dyestuff, which, in its native country, Mexico, was used as a dye and cultivated by artificial means at a remote period of history, was for a long time considered to be of vegetable origin. Cochineal, however, consists of the dried body of an insect, the Coccus cacti, which lives upon a species of cactus (the Nopalea coccinellifera (S.-Dyck) or Nopal], a plant which is found in the wild condition, but which, for the sake of the insect, is cultivated in gardens which are termed Nopaleries. The collection of the insects takes place before the commencement of the rainy season, and they are then brushed either into straw baskets or into basins of tinned iron. A number of insects are left upon each plant, and a new generation is produced, which is again gathered at a suitable period. The insects are killed by immersion in boiling water, or are enclosed in a linen bag and placed in an oven; by the latter process the peculiar white down covering the insect is preserved, but in the former case is lost.

In Mexico and Central America two varieties of cochineal are known the home-grown, or fine cochineal (grana fina), and the wild, or forest cochineal (grana silvestra) The former is more .valuable than the latter, and is richer in colouring matter. Since 1830 the cultivation of cochineal was introduced into Spain and the Canary Islands, Algeria, and Java, but the most productive of these newer plantations were those of Java. Since the discovery of the coal-tar colours, the consumption of cochineal as a dye-stuff has gradually decreased, and at the present time it is only employed in a minor degree. According to Liebermann, cochineal contains about 10 per cent, of colouring matter (Ber, 18, 19).

Carminic acid, the colouring matter of cochineal, was first isolated by Pelletier and Caventou (Ann. Chim. Phys., (2), 8, 250), and was subsequently examined by Preisser (Annalen, 52, 375; J. Pharm. Chim., (3), 5, 191) and Arppe (Annalen, 55, 101); but Warren de la Rue (ibid., 64, 1) was the first to isolate this substance in a pure condition, and described it as a purple-brown mass, which, on grinding, yields a bright-red powder, easily soluble in water and alcohol, but not in ether. The mean of his analyses gave 54.13 per cent, of carbon, 4.62 per cent, of hydrogen, and 41.25 per cent, of oxygen (by difference), and from these figures he deduced the formula C₁₄H₇O₈ or (C₁₄H₇O₈)₂.

Schützenberger (Ann. Chim. Phys., (3), 54, 52), on the other hand, was the first chemist who succeeded in obtaining carminic acid in a crystalline condition. He precipitated the colouring matter, from an aqueous cochineal extract, in the form of its lead compound, suspended this in water, and decomposed it with sulphuretted hydrogen. The carminic acid thus liberated dissolved in the water and was recovered from this solution by evaporation at a low temperature. The product, dissolved in alcohol, was treated with ether to precipitate certain impurities, and the liquid partially evaporated, when, on cooling, a crystalline mass was obtained, which Schützenberger considered to consist of two substances, carminic acid, C₉H₈O₅, and oxycarminic acid, C₉H₈O₆, the latter being distinguished by its solubility in ether.

Schaller (J., 1864, 410), who prepared carminic acid by the same method, assigned to it, however, the formula C₉H₈O₆.

The work of Hlasiwetz and Grabowski (Annalen, 141, 329) indicated that carminic acid was a glucoside which could be decomposed into a sugar and a new colouring matter, carmine red:
C₁₇H₁₈O₁₀ + 2H₂O = C₁₁H₁₂O₇ + C₆H₁₀O₅
Carminic acid. Carmine red. Sugar. but according to Liebermann (Ber., 18, 1969; Will and Leymann, ibid., 1 8, 318; and Von Miller and Rohde, ibid., 26, 2647), this is incorrect.

Coccinin, according to Hlasiwetz and Grabowski, is produced when carminic acid is fused with caustic potash. It crystallises from alcohol in straw-yellow needles or leaflets, dissolves in alkalis with a yellow colour, which, by air oxidation, develops first a green, then violet, and, finally, a purple tint. The analyses of this substance were in agreement with the formula C₁₄H₁₂O₅.

Ruficoccin. - By heating carminic acid with sulphuric acid to 130-140°C., Liebermann and van Dorp (Annalen, 163, 105) obtained a new colouring matter ruficoccin, C₁₆H₁₀O₆, and this consisted of a bright-red powder, sparingly soluble in hot water and ether, with a greenish-yellow fluorescence. On distillation with zinc-dust, it yielded a colourless crystalline hydrocarbon, C₁₆H₁₂, melting-point 183-188°C, from which, by oxidation, a quinone melting at 250°C. could be produced.

Fürth, somewhat later (Ber., 16, 2169), prepared the same hydrocarbon by the distillation of both cochineal carmine and coccinin with zinc-dust.

Ruficarmine, C₁₆H₁₂O₆, can be obtained, according to Liebermann and van Dorp, by heating carminic acid with water in a sealed tube at 200°C. It consists of a carmine-red powder, easily soluble in alcohol.

In view of the uncertainty existing as to the percentage composition of carminic acid, Schunck and Marschlewski (Ber., 27, 2980) submitted this substance to an elaborate process of purification, and, using in their operations as low a temperature as possible, obtained a product which crystallised from alcohol in red prismatic needles. Their analyses agreed closely with that required by the formula C₁₁H₁₂O₆, and the percentage composition approximately with the figures given by Warren de la Rue, and also by Schützenberger.

On the other hand, analyses by Miller and Rohde (Ber., 30, 1762) pointed to the formula C₁₂H₁₁O₇ or (C₁₂H₁₁O₇)₂, but according to the more recent work of Liebermann, Horing and Wiedermann (Ber., 1900, 33, 149), it now appears that the correct formula for carminic acid is C₂₂H₂₂O₁₃.

The most simple method of purification of carminic acid is that devised by Miller and Rohde. A solution of the crude colouring matter in five times its weight of water is diluted with four times its volume of acetic acid. The filtered liquid, on standing over sulphuric acid, gradually deposits the carminic acid in a crystalline condition.

Carminic acid crystallises in red prisms, easily soluble in water and alcohol, with a purple-red colour. It possesses no melting-point, but darkens at 130°, and at 250° becomes quite black.

By the action of alcoholic potassium acetate, carminic acid (Perkin and Wilson, Chem. Soc. Trans., 1903, 83, 139) yields two potassium salts, viz.:
Monopotassium carminate, C₂₂H₂₁O₁₃K, which is red coloured; and Dipotassium carminate, C₂₂H₂₀O₁₃K₂, soluble in water with a violet-red coloration.

Hexabenzoylcarminic acid, C₂₂H₁₆O₁₃(C₇H₅O)₆, obtained by digesting carminic acid with benzoyl chloride (Liebermann, Horing and Wiedermann), is an orange-coloured powder, easily soluble in benzene.

Octacetylcarminic acid, C₂₂H₁₄O₁₃(C₂H₃O)₈, crystallises in goldenyellow needles, melting-point 155-165°, and is readily prepared by the action of acetic anhydride in presence of zinc chloride or sulphuric acid on carminic acid (Miller and Rohde).

Ventilago madraspatana(CHAPTER I. The Anthraquinone Group.)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Ventilago madraspatana (Gaertn.) is a large climbing shrub belonging to the order Rhamnaceæ, the root-bark of which furnishes a dyestuff much valued in Southern India. It is very common in the Western Peninsula from the Konkan southwards, as well as in Ceylon and Burma, and, according to Lostard, it is collected in Mysore at certain periods of the year and exported to other districts of India.

The following are a few of its vernacular names: pitti (Hindi); raktapita (Bengali); pappili-chakka, surralpattai (Tamil); poplichukai (Kan); lokandi, kanwail (Bomb).

The root-bark appears as dark purplish-brown scales, ribbons, or filaments, the dust from which, when it is ground to powder, irritates the throat in a marked manner. When treated with boiling water or alcohol it gives a red solution, which on addition of caustic alkali, changes to a deep crimson.

Perkin and Hummel (Chem. Soc. Trans., 1894, 65, 923), who examined this dyestuff, extracted the root-bark with carbon disulphide, and obtained in this manner a resinous colouring matter, ventilagin, together with the crystalline non-tinctorial substances described below.

Ventilagin, C₁₅H₁₄O₆, consists of a reddish-brown brittle resin which, when distilled with zinc-dust, gives α-methyl anthracene, and when treated with zinc-dust in alkaline solution behaves as a derivative of methyl anthraquinone. Dilute alkalis dissolve it with a purple-violet coloration, and the corresponding salts are obtained as violet precipitates on adding sodium or potassium chlorides to these solutions. According to Perkin and Hummel, ventilagin is possibly allied to alkannin C₁₅H₁₄O₄, the colouring matter of alkanet, Anchusa tinctoria (Lam.), and may differ from this merely by the possession of two additional hydroxyl groups.

Emodin monomethyl ether, C₁₆H₁₂O₅, melting-point 200°, consists of orange-red needles, and is identical with that subsequently isolated from the root of the Polygonum cuspidatum (Sieb. and Zucc.) (Perkin, Chem. Soc. Trans., 1895, 67, 1084). A similar, if not identical, substance was isolated by Schwabe (Arch. Pharm., 1888, 26, 569), and by Thorpe and Miller (Chem. Soc. Trans., 1892, 64, 6) from the bark of the Rhamnus frangula (Linn.), and it is also present in rhubarb and the Rumex ecklonianus (loc. cit.) and Goa powder.

Trihydroxy-a-methyl anthranol-monomethyl ether (A), C₁₆H₁₄O₄, colourless needles, decomposes about 260° before melting, and is soluble in alkaline solutions with a yellowish-brown coloration. On gentle oxidation with chromic acid it is converted into emodin methyl ether, melting-point 200° (loc. cit.), and the same reaction takes place when its alkaline solution is oxidised with hydrogen peroxide. It closely resembles the dehydro-emodin anthranol monomethyl ether, subsequently isolated from Goa powder by Tutin and Clewer (Chem. Soc. Trans., 1912, 101, 290).

Trihydroxy-a-methyl anthranol-monomethyl ether (B), C₁₆H₁₄O₄, pale yellow needles, melting-point 173°, when oxidised with chromic acid is also converted into the emodin methyl ether, melting-point 200°. As two methyl anthranols are capable of existence, the isomerism of these compounds may possibly be thus explained: [KUVA PUUTTUU]

Substance C₁₆H₈O₈, orange-red crystalline powder, melting-point 275-280°, is soluble in alkaline solutions with an orange-red coloration, and when heated with zinc-dust gives a hydrocarbon which resembles α-methyl anthracene.

Substance C₁₇H₁₂O₅? is a chocolate, crystalline powder, soluble in dilute alkali with a yellow coloration, and this solution, on exposure to air, deposits a blue amorphous precipitate.

Dyeing Properties.

On striped printed calico the root-bark gives with alumina mordant a claret-red, not unlike that of alizarin bordeaux; with iron mordant a greyish-lilac, which in strong colours approaches a black; and with a mixture of the two a very purplish dark chocolate. The colours are moderately fast to soap, although considerably behind the alizarin colours in this respect. On oil-prepared calico ventilago gives with alumina mordant a rich claret brown, with chromium mordant a very black purple, and with iron mordant a good purplish-black shade. On wool chromium mordant gives a good purplish-brown, alumina a bordeaux red, tin a brighter red similar to an alizarin red with alumina mordant, and iron mordant gives dark dull purple and black. On silk similar colours are produced. No difficulty is experienced in dyeing with ventilago, and no additions to the dye-bath are necessary, except in the case of wool, with which it is desirable to add calcium acetate in order to correct the strong acidity of the mordanted fibre. Owing to the slight solubility of the colouring matter in water, the dyeing does not commence until the temperature reaches 70-80°. The root-bark appears to contain from 8-10 per cent, of ventilagin.

Onosma echoides(CHAPTER I. The Anthraquinone Group.)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Onosma echoides is a biennial plant frequent throughout the Western Himalaya from Kashmir to Kumaon. It is widely distributed from Siberia and Carbut to France (Watt's "Dictionary of Economic Products of India," 1891, 5, 487). The roots are violet coloured and yield a dye which is readily extracted by alcohol, giving a red solution, but this is very sparingly soluble in water. In various districts of India it is employed for dyeing wool, and on account of its solubility in oils and fats, to which it imparts a red colour, is also used as a substitute for alkanet. According to Watt (loc. cit.} the bruised root is employed medicinally as also are the leaves and flowers of this plant.

The general properties and colour reactions of the dye present in the root are very similar to those given by alkanet, and there can be little doubt that it contains either the same or closely allied colouring matters (Perkin, private communication).

Anchusa tinctoria, Alkanet(CHAPTER I. The Anthraquinone Group.)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

The Arabic name Al-henneh, modified to alkanna or al-kenna, was originally applied to the lythraceous shrub Lawsonia alba (Lam.), the root of which was described as Radix Alkanna vera, in contradistinction to the root of our alkanna, which is Anchusa tinctoria (Lam.), and which became known as Radix Alkanna spuria tinctoria. The latter, or False alkanet, is also known as Orcanette, Fr.; Orkanet, Ger.; Languedoc bugloss or dyers' bugloss, Radix Alkanna spuria. A rough plant with downy spear-shaped leaves, and clusters of purplish or reddish flowers; belongs to the Boraginaceæ. Found in Asia Minor, Greece, Hungary, etc. The roots, which have an astringent taste, occur in commerce, varying from the thickness of a quill to that of a finger.

Alkanet is one of the more ancient dyestuffs, having been employed by the Romans, but, on the other hand, it does not appear at any time to have attained such importance as madder, indigo, or even turmeric. The colouring matter of alkanet, known as anchusin or alkannin, has been examined by several chemists, but it is doubtful whether this compound has as yet been obtained in a chemically pure condition. Its composition is variously given as C₁₇H₁₀O₄ (Pelletier, Annalen, 6, 27), C₃₅H₂₀O₈ (Bolley and Wydlers, Annalen, 62, 41), C₁₅H₁₄O₄ (Carnelutti and Nasini, Ber., 13, 1514), and C₁₅H₁₄O₄ or C₁₅H₁₂O₄ (Liebermann and Romer, Ber., 20, 2428).

Alkannin forms a dark red amorphous powder possessing a beetlegreen iridescence, is readily soluble in most of the usual solvents, and its alkaline solution is deep blue coloured. On distillation with zincdust it gives, according to Liebermann and Romer, both methyl anthracene and anthracene.

Diacetylalkannin, C₁₅H₁₂O₄(C₂H₃O)₂, forms a dull yellow microcrystalline powder (C. and N.).

According to Eriksson (Ber. Deut. pharm. Ges., 1910, 20, 202), alkannin consists of two red pigments, the one being coloured green and the other blue by the action of alkalis. Red crystals have been observed by Tschirch in spaces in the cortex of old specimens of alkanet root. As alkannin is insoluble in water, in dyeing with alkanet an alcoholic extract is usually employed; and with aluminium and iron mordanted fabrics, violet and grey shades are respectively produced. These colours, however, are not fast to light, and are somewhat readily affected by weak alkalis or acids.

Haussmann of Mulhouse introduced alkanet into calico-printing, and for a short time it appears to have played a quite important part, but it is now little if at all employed in Europe for ordinary dyeing purposes. It is still used for colouring artificial wines, pomades, hair-oils, sweets, etc., and for these purposes it is well adapted on account of its ready solubility and harmless nature.

Bättger (J. f. prakt. Chem., 107, 146) and Eng (Jahres., 70, 935) recommend the use of papers stained by alkanet as indicators in alkalimetry.

According to Jolin (Chem. Schriften liber Alkanna, iv., 84), Thomson (Pharm. J., [3], 16, 860), and Eriksson (loc. cit.), alkanet root contains from 5-6 per cent, of anchusin.