COLOURING MATTERS OF LICHENS .

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alcohol, ether, and ammonia. These two substances are separated either byprecipitation with hydrochloric acid, and subsequent solution of the erythrinein hot water, or by adding chloride of calcium to the ammoniacal liquor,whereby the roccellic acid is separated as insoluble roccellate of lime. Since,however, ammonia also dissolves a brown matter present in the lichens, thepurification of the erythrine is not so easy as when milk of lime is used.

Bromine converts erythrine, in presence of ether, into a crystalline bromatedproduct, insoluble in water, but soluble in alcohol.

Picroerythrine, is a solid, white, very bitter body, sparingly

soluble in cold water, readily soluble in boiling water; soluble, also, in alcoholand ether. It may be obtained from its concentrated aqueous solutions incrystals ; it fuses at 158°; its reaction with test-paper is slightly acid, Withbromine, in presence of ether, it yields a bromated compound. If heated in asealed tube, orcine is formed. It is soluble in alkalies in the cold ; its ammo-niacal solution reddens easily on exposure to air. Neutral acetate of leaddoes not yield a precipitate with picroerythrine, but with the basic acetate aprecipitate is produced containing 68*94 P er cent °f oxide of lead ; perchlorideof iron gives a purple colouration ; ammoniacal nitrate of silver is reduced tothe metallic state. Prolonged boiling with water does not affeft picroerythrine,but if, at the same time, baryta or lime is present in excess, water is fixed,orcine, and erythrite, and an alkaline earthy carbonate are formed. This re-aftion is greatly accelerated at 150°, in sealed tubes. Picroerythrine isobtained by boiling erythrine with water, when it dissolves gradually, and theconcentrated liquid yields a brown glue-like mass, which gradually becomescrystalline : on treating this mass with cold water impure orcine dissolves,while picroerythrine remains as a residue. Instead of water alcohol can betaken, and, according to Dr. Stenhouse, erythrine should be treated with limeprevious to boiling, in which case the conversion is far more rapid.

Erythrite Synonyms: —Erythroglucine, erythromannite, pseudo-orcine,C4H8O4. This substance is an important member of the group, inasmuch asthe researches of Dr. Hesse and De Luynes have proved that erythrite a&s asa tetratomic alcohol, of which erythrine and picroerythrine are the orsellicethers; orsellic acid is itself triatomic, and its rational formula is, according

to Dr. Grimaux, j 0 3 .

Without' entering here into hypothetical details, we prefer to mention theprocess of preparation of erythrite and orcine as suggested and carried out byM. de Luynes. Lima lichens are exhausted with milk of lime, the filteredliquid is precipitated with hydrochloric acid; the erythrine thus obtained iswashed, and next heated for two hours in a closed iron vessel, at 150°, alongwith a certain quantity of milk of lime, too small to effefl the entire decom-position of the substance : the carbonate of lime having been separated byfiltration, the liquid is evaporated slightly, when, on cooling, orcine separatesin the crystalline state ; the evaporation of the mother-liquor yields a crystal-line magma, consisting of erythrite and orcine, which latter is removed bymeans of ether. The erythrite is purified by solution in boiling alcohol, fromwhich it crystallises on cooling. The calcareous extracft may also be boiled,ln order to concentrate it; the lime may be removed by carbonic acid; theliquid, after removal of this deposit, is evaporated to dryness, and treated withuther to remove the orcine.

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