4io

DYEING AND CALICO PRINTING.

produced are similar to those of quercitron, but so fast as to be comparableto those of madder.

Before we enter into more details on the application of the yellow dye-stuffstreated of, we have to pay some attention to certain colouring matters re-sembling quercitron, and considered by some authors identical therewith,while others deny such identity ; these matters are the following :—

Rutin, also called rutic or rutinic acid, melin, phytomelin. According toHlasiwetz, this substance, obtained by MM. Weiss, Kummel, and Borntraegerfrom the leaves of the Ruta grctveolcns t does not at all differ from quercitrin,while Dr. Schunck and M. Stein* declare this opinion incorredt, and pronouncethis body entirely distinct from quercitrin by its composition and properties.Melin is less coloured than quercitrin, and the percentical composition ofthese bodies differs considerably; melin containing in ioo parts—Carbon,50*06; hydrogen, 5*65; but quercitrin — Carbon, 54*85; hydrogen, 5*15.Melin is also more soluble in water, hot as well as cold, as also in alcohol.The alcoholic solution of melin is precipitated by acetate of lead with agolden-yellow, but that of quercitrin with an orange-red. Melin is mostreadily obtained from the so-called Chinese yellow berries, the leaf buds ofthe Sophora japonica, which are exhausted with alcohol at 80 per cent; asmall quantity of hydrated oxide of lead is first added to the solution, inorder to eliminate impurities ; the ensuing precipitate is filtered off, and tothe filtrate is next added a larger quantity of the same oxide, and the ensuingyellow precipitate, after having been collected on a filter and washed, issuspended in alcohol and decomposed by sulphuretted hydrogen. The sul-phide of lead having been filtered off, the solution yields, on evaporation, agolden-yellow crystalline substance, which is melin, and which by beingboiled with dilute mineral acids is split up into glucose, and a new yellow body,melletin, somewhat like quercetin. The formula of melin is, according toM. Stein, Ci 8H 24 O i2 , while Zwenger and Drouke maintain that the formulaof melin, a substance quite distindt from rutin, which latter they extra&edfrom capers ( Capparis spinosa ) and Ruta graveolcns , as well as from horse-chestnuts, is C 25 H3 2 0 I7 .

Robinin has been extracted by the last-named chemists from the freshflowers of the acacia tree, Robinia pseudoacacia. The flowers are exhaustedwith water, and the solution evaporated to the consistency of a syrup, thentreated with alcohol; and the extradt when evaporated to a small bulkdeposits yellow crystals, which are washed with cold alcohol and dissolved inhot water. The solution is partially precipitated by acetate of lead, and theensuing precipitate having been filtered off the slight excess of lead is re-moved by sulphuretted hydrogen from the yet hot solution, which, on cooling,deposits yellow crystals of robinin. It is a neutral, insipid substance, verysparingly soluble in cold water and alcohol, but more freely in these fluidswhen hot; and insoluble in ether. It fuses at 195 0 to an amorphous mass,which in contadf with water combines therewith, and crystallises. Robininis soluble in alkaline solutions with a yellow colour; nitric acid converts itinto oxalic and picric acids. If boiled with dilute sulphuric and hydrochloricacids it is split up into an amorphous and unfermentable glucose, and intoquercetin. The glucose yields, on treatment with nitric acid, oxalic and picric

* “Journal fur Praktische Chcmie,” lxxxv., 351; and lxxxviii., 280.