736 



2. Alpha- Or sellesic acidwsis obtained by mixing crude gelatinous 

 orsellic acid with a little water, neutralizing with lime or baryta, and 

 precipitating with muriatic acid. A gelatinous hydrate is obtained, 

 which may be purified by solution in dilute alcohol and crystallization. 



The composition of this acid and its baryta salt is as follows ; — 



Alpha- Orsellesic acid Cig Oj. + HO 



Alpha- Or sellesiate of baryta Cje Hg 074-BaO. 

 This acid gives a fugitive bluish-red or violet tint with hypochlo- 

 rite of lime. Orsellic acid gives a deep blood-red tint, quickly 

 changing to yellow. 



3. Orsellesic ether, Cje Hg + C4 H5 O, is obtained from alj)ha-or- 

 sellic acid by boiling in strong alcohol, evaporating to dryness, and 

 dissolving in boiling water. It crystallizes on cooling in long flat 

 needles, having a yellowish colour from adhering resin. 



II. Roccella tinctoria from the Cape of Good Hope. 



By processes similar to those just mentioned, this lichen yielded 



1 . Beta- Orsellic acid C34 Hi- O14 -f HO 



Beta-Orselliate of baryta .... C34 H17 Oj^ + BaO. 



2. Beta-Orsellesic acid (formula to be given hereafter). 



3. An ether compound, which is probably orsellesic ether. By 

 three experiments its composition was found to be — 



I. II. III. 



C 60-82 60-75 60-83 



H 6-27 6-15 6-27 



O 32-91 33-10 33-00 



100-00 100-00 100-00 



4. RoccelUnin. — Obtained by drying the gelatinous mass which is 

 precipitated from the lime solution by muriatic acid, and boiling in 

 strong spirit. The ether compound dissolves, and roccellinin remains 

 behind. It is purified by repeated crystallization from strong spirit, 

 aided by animal charcoal, and presents itself in soft hair-like crystals 

 about an inch long, arranged in stars. It is a very indifi^erent sub- 

 stance, appearing however to be a feeble acid. 



Its empirical formula is C38 H17 O15. 



III. Roccella Montagnei. 

 By similar treatment yielded — 



1 . Erythric acid C20 Hio O9 + HO . 



This acid gives a blood-red colour with hypochlorite of lime. 



2. Erythric ether C20 Hio O9 + C4 H^ O . 



3. Erythric methylic ether C20 Hjo Og-f Cg H3 O. 



This ether crystallizes in longer and narrower prisms than erythric 

 ether. 



4. Eryihrelesic acid is analogous to alpha- and beta-orsellesic acids. 



5. Picro-crythrin By neutralizing- erythric acid with lime or 



