On the Formation of Indigo from the Woad 

 (Isatis tinctoria)''. 



Proceedings of the Section <>{ Sciences, Kon. Akadeniie van Wetenschappen, Amster- 

 dam, Vol. II, 1809, blz. I20~ijr,. — X'erscheen onder den titel »Ovcr de indigovorming 

 uit de Weede (Isatis tinctoria). in Verslagen Kon. Akademie van Wetenschappen 

 Wis-en Natuurk. Afd., .Amsterdam, Deel VU, 1899, blz. 91— 99. 



Some years ago I wished to become acquainted with the so-called «indigo-fermen- 

 tation«, about wliich nearer particulars had been communicated by Mr. .'Mvarez. 

 He examined Indigofera and says'): 



»If a decoction of the plant is prepared and sterilised after passing it into test-" 

 tubes or Pasteur's-flasks, the reddish colour of the liquid remains many months un- 

 changed without the appearance of indigo. But if some microbes of the surface-mem- 

 brane of an ordinary indigo-fermentation are adiled, as also the special active bacterv 

 of it in an isolated condition, after some hours an abundant indigo-formation is ob- 

 served.« 



Ithen triedtomakefrom \voad(/.'a(/.f tnicturiaj.ht which.according to the Iiterature, 

 indican, i. e. the same indigo-producing substance as in the other indigo-plants should 

 be present, a decoction with which I might repeat the experiment of .Mvarez. But I 

 could, neither by boiling, nor by extraction at low temperature, obtain from this plant 

 a sap which remained unchaiiged at the air. Constantly, after a .sort time, indigo 

 will separate out of it, without there being any question of the influence of bacteria 

 or enzymes, so that the word »indigo-fermentati(in« would here be quite misplaced. 

 Neither do purposely added bacteria or enzymes favour the indigo-formation fr<im 

 woad-decoction. 



Later, however. 1 was enabled to convmcc myself that the statement of /Mvarcz 

 is correct, as well with regard to the decoction of Indigofera leptostachya as to th.it 



') It was first niy intcntion to treat »On tlie function of enzymes and bacteria 

 in the formation of indigO'". I have declined this plan for the moment, and givc now 

 only part of my e.xperiments, because I see that also Mr. Haze winkel, of the Ex- 

 perimentstation for Indigo at Klatcn, Java, has obtained important results about that 

 very subject, which results, for particular reasons, have however been imparted till 

 now to a few experts only. Yet I cannot avoid mentioning some facts, found by me, 

 the priority of which perhaps pertains to Mr. Hazewinkel, without niy being able 

 to acknowledge bis claim. One indiscretion, however, I am obliged te commit: Mr. 

 Hazewinkel has, already before me, established the fact, that by the action of the 

 indigoenzyme and of acids on indican, indoxyl is produced. 



') Comptes rendus, T. 105, pag. 287, 1887. 



