FLAVIN 403 



stuffs in a weak soda-solution, saturating with sulphuric or hydrochloric acid, and 

 boiling for half-an-hour. The inventor claims that the products thus obtained differ 

 from the original substances in being free from tannin and lime (?), and in having 

 acquired new properties, viz. a greater affinity for mordants and a more vivid and 

 richer colour. Being less soluble in water, they are preferable for the dyeirg of such 

 tissues as require a boiling heat in the vat. 



' Since particular stress is laid upon the increase of the intensity of the colour, it is 

 to be assumed that the flavine contained then a larger proportion of quercitrin. 

 Although the patentee fails to give hints with regard to this point, my supposition 

 has been confirmed by the results of an examination of flavine imported in 1858 into 

 Germany, made by Koenig. I am unfortunately not in possession of the original 

 paper, yet according to Gmelin, Kcenig obtained quercitrin in minute crystals by 

 treating the flavine with very dilute boiling sulphuric acid, and by purifying the 

 separated flocculent precipitate the ordinary manner. However, it will always 

 remain a disputed point whether Leeshing was or was not acquainted with the papers 

 on quercitrin by Kigand, who first communicated the fact that this substance is split 

 up if acted upon by dilute mineral acid. This paper appeared in the " Chemical 

 Gazette," two years previous to the date of Leesliiug's patent. I would remark that 

 Rigand was well aware of the fact that mordanted cotton assumes a purer yellow when 

 dyed with quercetin than when dyed with quercitrin. 



' With regard to the process of Leeshing for enhancing the colouring power of the 

 yellow oak, Bolley, in his " Chemische Technologic der Spinnfasern," says that it was 

 not rational, the quercetin formed being deposited on the bark. But the learned 

 technologist failed to consider that the process in question was also applied to flavine, 

 which was already then a commercial commodity ; and, moreover, we may well accept 

 that it was not the intention of Leeshing to extract the colouring matter, partly 

 because the weighty bark with enhanced colouring power brought a proportionally 

 higher price than the pure dye-stuff, and partly because the demand for the latter (the 

 flavine) was undoubtedly not yet sufficiently large. When considered in this light, 

 the inventor certainly deserves credit. One of the processes is quite analogous to the 

 preparation of garancine from madder. In both cases a substance combined with 

 glucose must be set free to be converted into a dye-stuff. In short, the " quercitrin " 

 of Leeshing is a technical product from quercitron. 



' After the beautiful researches of Bolley and Rigand on quercitrin had already 

 been published, it is incomprehensible that Muspratt (vide his " Chemistry applied 

 to the Arts and Manufactures," edition of 1860), in treating of the above-mentioned 

 dyes, states that their intensity was probably enhanced because the colouring matter 

 had become more soluble in water. Yet on the very same page, in giving an abstract 

 of the Patent Specification of Leeshing, he mentions that the derivates in question upon 

 being treated with hot as well as cold water, yield much less colouring matter than 

 the materials from which they had been produced. Schlumberger, according to 

 Grothe, treats the bark of the yellow oak as follows : 100 kilos of the ground wood 

 are mixed with 280 litres cf water, acidulated with 25 kilos of oil of vitriol. This 

 mixture is boiled for two hours, whereupon the bark is washed out, pressed and dried. 

 For the same quantity of bark Schlumberger takes four times the quantity of acid (of 

 only one-third the strength) of that of Leeshing, but extends the time of treatment to 

 twice the length. These are the only points in which these two methods differ from 

 each other. In speaking of this process, Grothe, in his " Katechismus der Bleicherei, 

 Farberei, und des Zeugdrucks" (p. 103), remarks: "All the tannin having been 

 separated by treating the bark with sulphuric acid, the colours produced with quercetin 

 are much purer and brighter than those obtained with flavine." I am at a loss to 

 comprehend this, for it must be evident to every one that the ground bark, when 

 directly treated with acids, must always contain a larger amount of intermediary 

 products than flavine, even when this latter has not been washed out. Grothe, more- 

 over, observes: " Dye-extracts from quercitron, which contain mainly quercitrin, yield 

 with alum a beautiful yellow." I ask, how is it possible that extracts from quer- 

 citron, among which Grothe includes the flavine, dye a beautiful yellow, if yet con- 

 taining tannin, which, according to Grothe, acts injuriously? And why have extracts 

 of quercitron been produced " with a high percentage of quercitrin," since " recent 

 investigations have demonstrated that they contain quercetiu, which is principally 

 effective ? " 



' Immediately after this, Grothe remarks : " For this reason the quercetin is now 

 especially made." If Grothe designates with this name the prepared bark of Schlum- 

 bergor, he will excuse me for asking why it is that it is not preferable to produce the 

 flavine, which, with regard to purity and intensity of colour, is to the yellow bark as 

 the purpurine of Kopp to the madder of Alsace ? 



4 With regard to the behaviour of the peculiar kind of tannic acid contained in the 



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