150 EESINS, BITTEE PRINCIPLES, ETC. 



and with alkaline solutions at a temperature as low as the boiling- 

 point. ^ Both this and the foregoing acid form salts of ethyl when 

 boiled with alcohol. 



Gyrophoric acid, which is sparingly soluble in ether, yields orcin 

 on decomposition with alkali, and turns red on exposure to am- 

 moniacal air.- 



PareUic acid, which is only slowly coloured under the same 

 conditions. 3 



CeratophjlUn, which strikes a violet colour with ferric chloride 

 and blood-red with chlorinated lime.'* 



PatcUaric acid, Avhich, in alkaline solution, turns red when ex- 

 posed to the air. Ferric chloride colours it blue ; chlorinated 

 lime, blood-red.^ 



Evernic acid yields orcin by dry distillation, is coloiured dark- 

 red by ammoniacal air, but only yellow by chlorinated lime.*^ 



Evcrninic acid (oxyusnetinic acid 1) is also coloured yellow by 

 chlorinated lime, but does not change when exposed to ammonia- 

 cal air. 



Usnic acid behaves in a similar manner, l)ut an alkaline solution 

 turns red on exposure to air, and the acid itself yields betaorcin 

 by dry distillation.'' 



Carbusnic acid^ (is sparingly soluble in ether) gives no colour 

 reactions. 



Vidpinic acid (chrysopicrin), which is more easily soluble in 

 bisulphide of carbon and chloroform than in ether, is obtainable 

 in yellow crystals and forms yellow salts with alkalies. Boiling 

 with baryta-water resolves it into alphatoluic acid, oxalic acid, 

 and methyl-alcohol.^ It may therefore be placed in the group of 



^ Schunck, Annal. d. Chem. und Pharm, xli. 157, 1842 (Journ. Chem. Soc. 

 i. 71) ; liv. 261, 184.''j ; Ixi. 64, 1847 ; Stenhouse, ibid. Ixviii. 57, 1848 ; cxxv. 

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



- Compare Stenhouse, ibid. Ixx. 218, 1849. 



3 Compare Schunck, ibid. liv. 274, 1845 ; Strecker, Ixviii. 114, 1848. 



^ Compare Hesse, ibid. cxix. 365, 1861. 



'' Compare Weigelt, Journ. f. prakt. Chem. cvi. 28, 1869. 



6 Compare Stenhouse, ibid. Ixviii. 86, 1848 ; Hesse, ibid, xlvii. 297, 1861. 



^ Compare Knop, Annal. d. Chem. und Pharm, xlix. 103, 1843 ; Kochleder 

 and Held, ibid, xlviii. 1, 1843 ; Stenhouse, ibid. Ixviii. 97, 114. Knop and 

 Schnedermann, Journ. f. prakt. Chem. xxxvii. 363, 1843 ; Hesse, Annal. d. 

 Chem. und Pharm, cxvii. 343, 1861. 



8 See Hesse, ibid, cxxxvii. 241, 1866 ; Ber. d. d. chem. Ges. x. 1324, 1877 

 (Journ. Chem. Soc. xxxii. 896). 



■* Stein, Chem. Centralblatt, 556, 1864 ; 432, 1865. See also Spiegel, Ber. 

 d. d. chem. Ges. xiii. 1629, 1880. 



