Ryan and O'Riordan — Tinctorial Constituents of some Lichens. 103 



D. — Physcia Parietina De Not. 



Physcia 'parietina, which is a very widely distributed and well-known 

 lichen, is not much used in dyeing. 



Mrs. A. Mackay, in the pamphlet already referred to, states that a yellow 

 lichen which grows on rocks just above the high-water mark imparts a rose- 

 pink colour to wool mordanted with dichromate. It does not seem to have 

 been used to any extent in Ireland ; Sullivan, O'Cuiiy, Eutty, and Smith 

 make no reference to its tinctorial properties. 



E. Paterno (Gazetta Chim. Ital. 188-2, pp. 231-261) isolated from this 

 lichen an acid which he termed fiscic acid, and which consisted of reddish 

 brown crystals, melting at 204" C, and dissolving in alkalis to form red 

 salts. 



0. Hesse examined the lichen later (Liebig's Annalen,284(1895), pp. 157- 

 191) and found in it Paterno's fiscic acid, which, however, owing to its 

 quinonic character, Hesse termed physcione. He showed also that its formula 

 is CisHjjOs, that it yields a diacetate and a dibenzoate, and that it reacts with 

 hydriodic acid to form protophyscione, CuHi^Og, melting at 198" C, and 

 protophyseihydrone C15H12O5, meliing at 210° ('. 



Later (Liebig's Annalen, 388 (1912), pp. 97-102), Uesse showed that 

 physcione on demethylation, by means of concentrated sulphuric acid at 

 160° C, formed frangula-emodin, and also that on methylation it yielded 

 frangula-emodin-trimethylether. Further the protophyseihydrone obtained 

 by the action of hydriodic acid on physcione was shown to be emodinol from 

 the identity of its acetylation product with emodinol-tetracetate. The con- 

 clusion drawn from these facts is that physcione is identical with frangula- 

 emodin-monomethylether. 



It has been shown by E. Leger (Journ. Pharm. et Chim. (7) 4 (1911), 

 p. 241), and by G. A. Oesterle (Archiv. der Pharm. 250 (1912), p. 301), that 

 aloe-emodin, with which frangula-emodin is very closely related, has the 

 formula A — 



OH CO OH 



I I A I I 

 \/\/\/CH20H, 

 CO 



which, apart from the weakly tinctogenic peri hydroxyls, contains no mor- 

 danting groups. Since, however, 0. Fischer and H. Gross (Journ. f. pr. Chem. 

 (2) 84 (1911), p. 369) regard frangula-emodin as a trihydroxy-methyl- 

 anthraquinone, having the three hydroxyls in the rings, it seemed possible 

 that this compound, and its derivative physcione, might possess marked 



