CATECHU.
493
mixture of two very closely allied homologous substances, which can beseparated from each other with great difficulty, viz., deutocatechuic acid,C16H16O8, and tritocatechuic acid, Ci 8H 20 C)8. Kraut and V. Delben, again,do not share Dr. Strecker’s opinion, and propose for catechuin the formulaCi2H I2 05 + 2H 2 0 ; Hlasiwetz and Malin prefer CigH^Os ; and the followingformulae, Ci 0 H I0 04 and C 22 H 22 0 9 , also agree with the results of the elementaryanalysis. It is clear, therefore, that the true formula for catechuin can onlybe settled by deduction from the products derived from it, and to thesederivatives we have now to turn our attention.
When catechuin is boiled with dilute sulphuric acid, with exclusion asmuch as possible of air, or boiled with alcohol, previously saturated withhydrochloric acid gas, it is converted into a brown amorphous body, insolublein water and alcohol, catechuretin, which appears to be formed by dehydrationfrom catechuin; the formulae assigned to catechuretin are, according toM. Neubauer, C I7 H I4 0 7 ; Kraut and V. Delben, C I2 Hi 0 0 4 ; Hlasiwetz,CigH I4 06 = CigHi808 (catechuin) minus 2H 2 0, also C 22 Hi 80 7 .
When catechuin is fused with hydrate of potassa it is split up into phloro-giucin and protocatechuic acid, a reaction which Hlasiwetz represents by—C19H18O8 + O2 — C 7 Hg0 4 +zCgHgOg.
Proto- Phloroglucin.catechuicacid.
Catechuin yields with bromine-water an insoluble reddish matter namedbromo-catechuretin, the formula of which is, according to Kraut andV. Delben, Ci 2 Br 4 Hs0 4 , or CigHsBrgOg, according to Hlasiwetz and Malin.Chloride of benzoyl yields, when heated to 190° with catechuin, two newproducts, one of which, soluble in alcohol, appears to be monobenzoiccatechuin, while the other body, insoluble in alcohol, seems to be benzoiccatechuretin. When catechuin is heated to ioo° with hydriodic acid, theorganic substance is deoxidised and transformed into a yellow elasticgranular body, insoluble in water, alcohol, ether, and acetic acid; containingin 100 parts 63-90 carbon, and 5*0 of hydrogen, the remainder being oxygen.A solution of catechuin in acetic acid yields, upon the addition of pulverisedbinoxide of barium a white body, insoluble in boiling water, soluble in aceticacid, and precipitated from that solution in a crystalline state upon theaddition of water; the percentage composition of this body is—Carbon, 58*0 ;hydrogen, 4*70; the rest being oxygen. Catechuin is converted by bichromateof potassa as well as by dilute and hot nitric acid into a brown insolubleamorphous body ; that resulting from the adtion of bichromate of potassaconsists, in 100 parts, of—Carbon, 58-07; hydrogen, 3*42; the rest beingoxygen. This brown matter is readily soluble in dilute nitric acid, the resultbeing the giving off of carbonic and the formation of oxalic acid. With concen-trated nitric acid, catechuin yields a product analogous to picric acid.Catechuin absorbs oxygen very rapidly and completely in presence of alkalies,and such solutions become thereby first red, then brown, and contain in thatcondition some brown, ill-defined substances known as rubinic and japonicacids. Catechuin undergoes the same alteration when its aqueous solution isexposed to air, but the adtion is more slow; it is this reaction and property ofcatechuin, viz., its readily yielding by oxidation brown insoluble matters, which1S the basis of its application in dyeing and printing.