F. The Chemical Constitution of the Purpurigenic Matter.

The chemical analysis of the purpurigenic matter is mainly associated with the names of Bizio (1833-35), the brothers A. and C. de Negri (1875), Schank (1879), Lettelier, Friedlaender, and Dubois. The researches of these eminent scientists can hardly be properly understood and appreciated by non-chemists, including the writer of these lines. It is, however, of special importance for our study to underline the following results: (1) Already Bizio had ascertained that the dye-secretion of Murex trunculus contains an element of blue very analogous to indigo: 


 “I was only sent an ounce of the liquid from the Murex trunculus to Florence. However, the liqueur of this murex was separated from me into two different substances, an absurdity … it has a strange substance and totally analogous to indigo!” “Del liquore del Murex trunculus non mi fu dato di portarme a Firenze che solo un’oncia. Tuttavia il liquore di questo murice fu separato da me in duo sostanze diverse, una assura … ha sostanza assura e in tutto analoga all’indace!” (2) 


The researches of Prof. August Lettelier into the chemical constitution of the purpurigenic matter of Purpura lapillus have shown that it contains at least three substances: a yellow not susceptible to light, an applegreen developing into deep blue under the action of light, a gray-green developing under the same action into a crimson red. (3) Professor Friedlaender in analysing the dye furnished by Murex brandaris succeeded in isolating from it the 6′.6′ dibromoindigo (reddish violet); in the dye secretion obtained from Murex trunculus he discerned in addition a blue dye, the constitution of which he has not yet established.1

Last but by no means least comes Professor Dubois’ work (Recherches sur la Pourpre, etc.) which besides presenting the results of technical research in a form as intelligible to the general reader as possible, also contains many an illuminating remark bearing upon purple in antiquity. Professor Dubois replying to me from Lyons under date of May 20th, 1913 writes inter alia (among other things)


“As I indicated in my work on Purple and some other animal pigments in the Archives of Experimental and General Zoology, Paris, 5th Series, V.II, 1909, purple is a mixture of two pigments, red and blue. The latter especially is very close to indigo from a chemical point of view. It is much more abundant in Murex trunculus and for an artifice one could, I believe, obtain pure blue with this last marine gasteropod. “ “Ainsi que je l’ai indiqué dans mon travail sur la Pourpre et quelques autres pigments animaux en Archives de Zoologie expérimentale et générale, Paris, 5ème Série, V.II, 1909, la pourpre est un mélange de deux pigments, un rouge et un bleu. Ce dernier surtout se rapproche beaucoup del’indigo du point de vue chimique. Il est beaucoup plus abondant dans Murex trunculus et pour une artifice on pourrait, je crois, obtenir du bleu pur avec ce dernier gasteropode marin.”


Next after its intrinsic quality of stability, the new play of colour which it produces upon the fabric in sun-light is said in the ancient writers to have secured for the purple dye the high esteem in which it was held (See especially W. Adolf Schmidt op. cit. p. 157.) It must have come to many a reader as a surprise to be told by Professor Friedlaender: 


“The results confirm the expectations of nuance and authenticity that were justified by Kirtian reading of ancient literature, but they are likely to cause great disappointment to modern audiences. We are used to livelier and pure tones now, and I do not think they are today’s mankind that canunderstand the enthusiasm of our ancestors. If I am wrong, the ancient colors are now available to us at a price that would be more than 1000 times lower than the old world; … / We have a poor illusion; that the shine and the beauty of the antique purple are no longer able to spark our spoiled eyes. “71 “Die Resultate bestätigen durchaus die Erwartungen hinsichtlich Nuance und Echtheit, zu der die kirtische Lektüre der alten Literatur berechtigte, aber sie dürften dem modernen Publikum eine grosse Enttäuschung bereiten. /Wir sind gegenwärtig an lebhaftere und reine Tone gewöhnt, und ich glaube nicht, dass die heutige Menschheit die Begeisterung unserer Vorfahren auch nur wird verstehen können. Sollte ich mich irren, so standen uns jetzt die antiken Färbungen zu einem Preise zur Verfügung, der uns mehr als 1000 mal niedriger käme als der alten Welt;… /Wir sind um eine Illusion armer; der Glanz und die Schönheit des Antiken-Purpurs vermögen unser verwöhntes Auge nicht mehr zu blenden.”2

As a set-off against this disillusioning information, I should draw attention to the following passage in Dr. Dedekind’s Beitrag –


“About the magnificent color effect of these purple samples, her maker wrote to me: ‘on silk the reflections are magnificent on the thread the color is beautiful, but does not have the admirable transparency that it offers on silk.’ In fact, these purple samples, especially those on silk, showed the delightful play of colors so rightly praised by the ancients, that miraculous, delicious shimmer for which the expressions are available: : Angé, pheggos lumen, nitor, splendor, fulgor, color in suspectu refulgens, versicolor, splendens, sublucens, micans, ardens, etc. “74 “Über die prächtige Farbenwirkung dieser Purpurproben schrieb mir ihr Anfertiger: ‘sur la soie les reflets sont magnifiques sur le fil la couleur est belle, mais n’a pas cette admirable transparence qu’elle offre sur la soie.’ In der Tat zeigte sich bei diesen Purpurproben, insbesonderes jenen auf Seide, das von den Alten mit Recht so gepriesene entzückende Farbenspiel, jener wundersame, köstliche Schimmer, wofür die Ausdrücke vorliegen: Angé, pheggos lumen, nitor, splendor, fulgor, color in suspectu refulgens, versicolor, splendens, sublucens, micans, ardens, etc.”3


Compare also in this connection another passage in Friedlaender 


“They are also praised for a play of colors that emerges in the sun by name, presumably similar to the coppery shine that can be observed in intense indigo colors, And which we now call bronzing for several other dyes.” “Gerühmt wird ferner an ihnen ein namentlich in der Sonne hervortretenden Farbenspiel, vermutlich ähnlich dem kupfrigen Glanz, der bei intensiven Indigofarbungen zu beobachten ist, Und den wir bei zahlreichen anderen Farbstoffen jetzt mit Bronzieren bezeichnen.”4


In conclusion I may be permitted to observe that the case of Murex trunculus tends to show that there is a distinct relationship between the fastness of the purple colour and its development through the action of light.When one considers that the Murex trunculus develops its dye in darkness as well as in day light,5 and that contrary to its congeneric species (Murex brandaris) its dye is not fast,(76a – Lacaze-Duthiers, op. cit.) at least to washing, one is naturally led to think that the two characteristics are interdependent.



  1. Friedlaender, ibid.: “Untersuchungen haben ergeben, dass aus den Dursen von Murex trunculus neben dem rotvioletten Farbstoff auch noch ein blauer von noch nicht aufgeklärter Zusammensetzung erhältlich ist.”

    “Studies have shown that in addition to the red-violet dye, a blue of unex elucidated composition is also available from the durses of Murex trunculus.”

  2. Idem, p. 10.
  3. Dedekind, ibid., v.I, p. 23.
  4. Friedlaender, ibid., pp. 6-7.
  5. R Dubois, op. cit., p. 518: “On a prétendu que la lumière exerçait une action photographique sur le mucus purprigène de cette espèce (sc. Murex trunculus) c’est une erreur, partagée cependant par de Lacaze-Duthiers. D’autres ont dit que la lumière active a avive le couleur la couleur de ce pigment. Les expériences de A. et G. Negré sont contraires à cette opinion, etc.”


    “It has been claimed that light exerts a photographic action on the purprigenic mucus of this species (sc. Murex trunculus) it is an error, shared however by de Lacaze-Duthiers. Others said that the active light       brightened the color of this pigment. The experiences of A. and G. Negré are contrary to this opinion, etc.”