264 Mr. Schunck on the Substances 



substance had separated was evaporated to dryness, when it 

 left a dark green viscid residue, interspersed with yellowish 

 crystalline grains. This residue was treated with boiling 

 water, which removed some picro-erythrine contained in it, 

 and then with cold alcohol, which left behind a quantity of 

 the greenish-white fat just described, and acquired a dark 

 green colour. The alcoholic fluid had an acid reaction. It 

 contained roccellic acid and a dark green, easily fusible fat. 

 In order to separate the roccellic acid, an alcoholic solution 

 of sugar of lead was added. This produced a greenish-white 

 flocculent precipitate, which was separated by filtration and 

 washed with alcohol. This precipitate, consisting of roccel- 

 late of lead, was decomposed by dilute nitric acid, which left 

 the roccellic acid behind of a green colour. The latter, after 

 being washed with water to remove the nitrate of lead, was 

 dissolved in boiling alcohol, to which some animal charcoal 

 w T as added. After filtering the solution, the roccellic acid se- 

 parated on cooling in white crystalline needles. By adding 

 water to the green alcoholic fluid from which the roccellate 

 of lead had been precipitated, it became milky, and on boil- 

 ing, dark green drops of a fatty substance collected at the 

 bottom. This substance is a kind of fat, which is easily fu- 

 sible at the temperature of boiling water. Its green colour is 

 no doubt owing to the presence of chlorophylle, which cannot 

 however be separated from it. It imparts no colour to boil- 

 ing muriatic or dilute sulphuric acid. Boiling nitric acid de- 

 stroys its green colour and changes it into yellow, after which 

 it dissolves in alcohol with a yellow colour. It is soluble in 

 alkalies, and is precipitated again by acids. 



The lichen, after extraction with 'water and alcohol, was 

 treated with dilute caustic ley at a boiling heat. A dark 

 brown fluid was obtained, to which, after filtration, muriatic 

 acid was added. This produced a dark brown flocculent 

 precipitate, which, after filtering, washing with water and 

 drying, appeared as a light brown powder. When heated it 

 burns without leaving any ash. On being treated with strong 

 caustic potash at a boiling heat, it gives off a slight smell of 

 ammonia. It is soluble in alkalies, but insoluble in alcohol. 

 The acid fluid from which it was precipitated deposited on 

 evaporation a dark brown substance, in the same way as a 

 solution of tannin or extractive matter. It is doubtful indeed 

 whether the brown substance precipitated by the acid from 

 the alkaline fluid is contained in the plant as such, or whether 

 it is formed by the conjoint action of the air and alkali on 

 some other substance in the lichen. 



The Roccella tinctoria is easily reduced to ashes. These 



