Royal Society. 301 



I. South American variety 0/ Roccella tinctoria. 



The lichen was cut into small pieces and macerated with a large 

 quantity of water for some hours, then quick-lime was added. A 

 yellow solution was obtained, from which muriatic acid precipitated 

 the colouring matter, as a bulky gelatinous mass ; this was washed, 

 dried on a plate of gypsum, and dissolved in hot spirits of wine (not 

 boiling). The solution on cooling deposited the colouring principle 

 in small white prismatic needles arranged in stars. This is — 



1. Alpha- Or sellic acid (hydrated) C3.2H15 0,3 + HO 



and its salt of baryta — 



Alpha- Orselliate of baryta C3.2 H,3 0,,+ BaO 



2. Alpha- Or sellesic acid w&s 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- Or sellesic acid CioHgOj + HO 



Alpha- Orscllesiate of baryta Cjc Hs O7 + 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 

 clianging to yellow. 



3 . Orsellesic ether, Gig Hg Oj + C4 Hj O, is obtained from alpha-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 /rom the Cape of Good Hope. 



By processes similar to those just mentioned, this lichen yielded — 



1 . Beta- Orsellic acid Cj^ H,. O^ + HO 



Beta- Orselliate of baryta .... C^, H,; O,^ + 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. in. 



C 60-82 60-75 60-83 



H 6-27 6-15 6-27 



O 32-91 33-10 33-C9 



100-00 100-00 100-00 



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

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

 Blrong spirit. Tlic ctlier compound dissolves, and roccellinine remains 

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

 aided by animal charcoal, and jjresents itself in soft iiair-like crystals 

 about an inch long, arranged in stars. It is a very indifferent sub- 

 Btunce, appearing however to be a feeble acid. 



Its empirical formula is C33 II,; Oij. 



