a yellow Colouring Mailer. 197 



becomes brighter, while turmeric, which contains a blue and 

 yellowing colouring principle, has the former reddened by 

 acids, and the latter converted to a brown by alkalies. Moist- 

 ened yellow parietin paper, on the other hand, becomes red or 

 purple when freshly prepared, and reddish brown, if long pre- 

 pared, by coming in contact with ammonia and other alkalies. 

 The other reactions of parietin are simple. The alcoholic 

 solution is precipitated yellow by nitrate of silver and acetate 

 of lead, and other metallic salts. A solution of permuriate of 

 iron renders the colour much darker. The precipitates with 

 silver and lead have not been analysed, from the minute quan- 

 tity of parietin at my disposal. 



The yellow colour of the Parmelia parietina early attracted 

 the attention of those persons interested in dyes. It was ac- 

 curately described by Hoffmann, Amoreux, and Willemet, in 

 1786.* The latter informs us, that the Swedes in the pro- 

 vince of Oeland, obtained by means of this lichen and alum a 

 yellow dye for woollen stuffs, and that a flesh tint was also 

 procured from it, fitted for linen and paper ; that goats eat 

 this lichen ; and that Haller recommended it as a powerful 

 tonic in diarrhoea. He adds, that he had himself used it in 

 his practice as a tisan, and had found it to prove beneficial in 

 that form of the disease which occurs in autumn. Hoffmann 

 states, that in Norway, when boiled with milk, it is used as a 

 remedy in jaundice. This idea may have perhaps originated 

 from the correspondence in colour of the disease and cure, 

 upon the principle so much in vogue at present, " similia 

 similihus curanturT Hoffmann affirms that he never could 

 obtain a yellow colour from this lichen, but that with wine 

 vinegar he obtained an olive-green or fawn colour ; and with 

 true wine vinegar {aceto vini vero) and copperas, a flesh or 

 apricot shade. Of these colours he has appended to his essay 

 specimens, together with forty-nine others, obtained from 

 various species of lichens. Dr John P. Westring of Nord- 

 koping, in Sweden, who prosecuted an extensive inquiry into 

 the colouring matter of lichens, describes the Lichen parietinus 



♦ M^moires Couronnes en Tannee 1786, par TAcademie des Sciences, 

 Belles Lettres, et Arts, de Lyon, sur rUtilite des Lichens, dans la Me- 

 dicine et dans les Arts. 8vo, 1787. 



