372

DYEING AND CALICO PRINTING.

Erythrite yields large crystals belonging to the tetragonal system, somewhatsweetish to taste, neutral to test-paper, very soluble in water, less so inalcohol, almost insoluble in ether; it does not assume any colour, either by thecombined adtion of air and ammonia, or when in contact .with hypochloriteof lime. It is neither precipitated by basic nor neutral acetate of lead. Itfuses readily, and does not possess the colourable properties of the lichens.It is decomposed by caustic potassa, yielding hydrogen and acetic acid, andwhen heated to 240°, with that base, hydrogen and oxalic acid are formed.When treated with from 20 to 30 parts of concentrated sulphuric acid, at 6o°,erythrogluci-sulphuric acid is formed : the aqueous solution of this substanceis readily and rapidly oxidised when in contadt with air or with spongy pla-tinum. When dry erythrite is fused, and heated along with twelve times itsweight of hydriodic acid (sp. gr. 1*99), it yields, on distillation, hydriodate ofbutylen, C 4 HsIH.

Orsellic, or cr-Orsellinic, Acid, CsHsO^—Since orcine is diatomic, anddiffers from orsellic acid by having C0 2 less, the orsellic acid is, according toGrimaux, triatomic. This acid is best prepared by boiling the lecanorates oflime or baryta for a short time with water ; the ebullition should be carefullyconduced, since otherwise carbonate of lime and orcine are formed : the or-sellic acid is precipitated by means of hydrochloric acid ; the ensuing gelatinousprecipitate is treated with boiling alcohol or with warm water, and, on cooling,prismatic crystals are deposited. This acid is more soluble in water thandiorsellic and lecanoric acids ; its lime and baryta salts are also more soluble,and it is by far more soluble in ether ; its taste is sour and bitterish ; it reddenslitmus-paper; fuses at 176°, but is then also decomposed into orcine and carbonicacid. This reaction is also produced by long-continued boiling. Bleaching*powder gives it a fugitive violet-red colour. In contadt with air, causticammonia colours it red. The alkaline and alkaline-earthy orsellates aresoluble in water, but if any excess of base be present are readily decomposedinto orcine and the carbonate of the base. Orsellic acid, combined also withmethyl, ethyl, and bromine, converts it into tribromorcine.

c 8 h 5 o

Lecanoric, Diorsellic, a-Orsellic Acid, or Lecanorine, C8H5O O5.

H 4 )

—Schunck found this acid in lichens belonging to the species Lecanora andVariolaria , Rochleder and Held in the Evernia prunastri , and Stenhouse inthe Roccella tinctoria. It may be prepared by the following processThelichens, previously pulverised,, are exhausted with ether, the solution is evapo-rated to dryness, and the residue first treated again with ether, next withwater, and lastly dissolved in alcohol. The lichens may also be treated withmilk of lime or with ammonia, the liquids filtered from the insoluble residue,and the filtrate treated with hydrochloric acid ; the pasty precipitate is sepa-rated by filtration, well washed, dried, and next taken up with alcohol, fromwhich the acid crystallises. This acid then forms white acicular crystals,sparingly soluble in cold water and cold alcohol; soluble in ether, boilingalcohol, and acetic acid: 1 part of the acid requires for solution 2500 parts ofboiling water, 150 parts of alcohol at 15 0 , 5*15 parts of boiling alcohol, and80 parts of ether. Bleaching-powder colours it temporarily red. The alco-holic solutions of the acid are tinged purplish by the addition of chloride ofiron. When the acid is dissolved in ammonia, and left in contadt with air, it