the Roccella tinctoria and Evernia Prunastri. 257 



by means of boiling alcohol, and of orcine by means of alkalies, 

 takes place. 



The formation of erythrelesic and orsellesic acids still remains 

 to be explained. If the view here taken be the correct one, 

 it follows that these two acids must be identical with lecanoric 

 acid combined with one equivalent of water, i. e. C 18 H 8 () 9 

 Its composition would then be as fol- 



+ HO: 



lows 



ClS^gOg. 



Orsellesic acid. 

 A 



18 eqs. 

 9 ... 

 9 ... 



Carbon . 

 Hydrogen 

 Oxygen . 



1350 

 112-3 

 900 



57-14 



4-75 



38-11 



I. 



57-99 



5-25 



36-76 



II. 

 57*90 



5-08 

 37-02 



2362-3 100-00 100-00 lOO'OO 



The composition of erythrelesic acid not having been ex- 

 amined, it is impossible to arrive at any conclusion in regard 

 to it. 



I may here mention, that I some time ago discovered that if 

 lecanoric acid be dissolved in caustic baryta and again preci- 

 tated, it is found to have taken up one equivalent of water, 

 and been changed into C 18 H 9 9 , and this water it does not 

 again lose. This equivalent of water is replaced in the aether 

 compound by C 4 H 5 O ; so that it appears that this aether 

 forms no exception to the general rule, according to which 

 the oxide of ethyle in the aethers always replaces the water of 

 the hydrated acid. The body C 18 H 8 8 might still retain the 

 old name of lecanorine. 



Mr. Stenhouse' s evernic acid may also be shown to belong 

 to the same class of bodies as the preceding. Mr. Stenhouse 

 gives for evernic acid the formula C 34 H ]6 14 . I propose to 

 change this to Cgg H, 7 15 . It would then be composed as 

 follows : — 



Stenhouse. 

 a 



36 eqs. Carbon . 

 17 ... Hydrogen 

 15 ... Oxygen . 



4412-1 100-00 100-00 lOO'OO 



The potash and baryta salts, when calculated according to 

 this new formula, also give numbers which agree sufficiently 

 well with those found by Mr. Stenhouse. 



