§ 157. LICHEN ACIDS. 149 



plimbagin^ (coloured chetry-red by sniall quantities of alkalies), 

 polygmic acid,^ quasdn^ (which is soluble in water, can be removed 

 by shaking with benzene or chloroform. See also ^-55), rdilerin*- 

 simpirin,^ tanacetin,'^ tangMnin,'' taraxadn^ xylostmi^ xanthosderotin, 

 or sderoxanthin.^^ 



§ 157. lAchen Acids and allied Subsiances. — Amongst the consti- 

 tuents of plants that are solublfe in ether a number occurring in 

 lichens may finally be njentioned here. Some of them possess 

 the characters of aeids, as, for instance : 



BtiecelUc acid, which is itself insoluble in Water, but f orm&'soluble 

 alkahne salts. It can be detected in the gonidia by alkamia.1^ 



Others are characterised by yielding beatitifully coloured com- 

 pounds when acted upon by alkalies, ferric chloride or chlorinated 

 lime, properties that would indicate some relation to oicin and 

 allied bodies. Others, again, possess the chemical characters of 

 ethereal salts, being resolved by alkalies into stronger acids and 

 alcohols. To the former group belong the following ; 



Lecanoiie add (diorselUc acid); which is coloiired deep fed by 

 chlorina,ted lime (avoiding an excess^, and is decomposed at 153° 

 •into orcin and carbonic acid.^* 



Orsdlic a-flid^. which undergoes a similar decomposition at 17(5°, 



1 Compare Dolong, Jg;hrb. f. Pfiarm. xiv. 441. 

 " Compare Bademacker. 



* Compare Wiggera, Annal. d. Chem. und Pharm. xxi. 40, 1837; Gold- 

 Echmidt uiid Weidel, Ber. d. Wiener Akad. Ixxi7.,389, 1877 (■Tourn. Chem. 

 SOc. xxxiv. 80). See also my 'Ermittelung d. Gifte,' 2nd cd., 300 et. seq. ; 

 «(nd .Tahresb. t. Pharm. 619, 1878. Also Christensen, Arohiv d. Pharm. Xvii. 

 iSl, 1882. 



* GpiBpare Anderson, Chem. Centralblatt, 372, 1865 (Amer. Journ. Pharm, 

 JOaii. 325) ; Grotes; Jahresb. f. Pharm. 161, 1873(Phai-ra. Jonm. Trans. [3], 

 iu. 228). 



* Compare Peokolt, Zeitschr. d. Oesterr. Apotheker-Ver. 289, 1876 (Pharm. 

 Jomn. Trans. [3], yii. 69). 



' Compare Leroy, Journ. de Chim. med. xxi. 357 ; Leppig, ' Chem. Unters. 

 d. Tanacetum vulgare,' Disa Dorpat, 1882. 



'' Compare Heury, J oum. de Pharm. x. 52 (Amer. Journ. Pharm. viii; 102). 



* Compare Kjtrfnayer, ' i)ie Bjtterstoffe,' 97 ; iand Polex, Arohiv d. Pharan. 

 xiji. 50, 164(J. 



' Comp!U« Hiibschmanu, Pharm. Vierteljahresschr. v. 197 ; and Enz, ibid. 

 196, lS56. 



1" Compare Dragendorff and Podwissotzki, loc. cit. 



11^ Compare Schunck, Aunal. d. Chem. und Pharm. , Ixi. 66, 78; also Hesse, 

 cxvii. 332, 1861 (Journ. Chem. Soc. iii 153). 



'^ Schunck, AnnaL d. Chera. und Pharm. xli. 157, 1842 (Journ. Chem. Soc. 

 i. 71) ; liv. 261, 1845 ; Ixi. -64, 1847 ; Stenhouse, ibid. Ixviii. 57, 1848 ; cxxv 

 353, 1863 (Journ. Chem. Soc. xx. 221 ) ; Hease; cxxxix. 22, 1866. 



