the Roccella tinctoria and Evernia Prunastri. 259 



Mr. Stenhouse, however, added caustic potash to the alcohol, 

 so that any lecanoric acid or lecanoric aether present must 

 necessarily have been decomposed. 



I have still a few words to say in regard to Kane's erythry- 

 line. Kane has given this name to the colour-producing sub- 

 stance found by him in the Roccella tinctoria. It is analogous 

 to erythric acid ; but in composition it differs so widely from 

 the latter, as to preclude the supposition of their being iden- 

 tical. Since erythryline gives among the products of its de- 

 composition a body of the same composition as lecanoric 

 aether, I infer that it contains lecanoric acid in a similar state 

 of combination as in erythric, orsellic and evernic acids. Kane 

 gives as the formula of erythryline, C 22 H 16 O e . I propose to 

 change this into C 42 H^ 12 . The composition would then 



be as follows : — • 



Kane. 



. A k 



I. II. 



42 eqs. Carbon . 3150 66*85 66*88 65*53 

 29 ... Hydrogen 361*9 7*68 8*13 8*38 



12 ... Oxygen . 1200 25*47 24*99 26*09 



4711*9 100*00 100*00 100*00 



If this formula be adopted, it follows that — 



if from 1 eq. erythryline . . . =C 42 H 29 12 

 we subtract 1 eq. lecanoric acid =C ]8 H 8 O a 



C 24 H 21 4 

 and add 2 eqs. water . . . . = H 2 2 



the resulting formula is . . . C 24 Hgg 6 - /Urt-<J.l>u< o^^ 



Now C 24 H 23 6 is the formula which I have given in my 

 paper on the Roccella tinctoria for roccellic acid. It would 

 appear, therefore, that erythryline is equal to lecanoric acid 

 plus roccellic acid minus two equivalents of water. As Kane 

 has mentioned no experiments on its products of decomposi- 

 tion, no further reasons can be given for or against this view 

 of its composition. 



In my opinion, therefore, erythryline, erythric acid, orsellic 

 acid and evernic acid, are coupled acids, in which lecanoric 

 acid forms the acid ingredient, and they might be called re- 

 spectivelyfi'occell-lecanoric,Berypicrine-lecanoric^fiDrcine-leca- 

 noric andBfcvernesine-lecanoric acids. They resemble those 

 coupled acids, which consist of simple acids united with neu- 

 tral bodies, and which saturate the same quantity of any base 

 as the simple acids contained in them. They are similar to 

 hippuric acid, which may be considered as a compound of 



