An examination of the petals of the red rose " George Dickson " has shown that the anthocyan pigment contained therein is the cyanidin glucoside, cyanin. It is present to the extent of about 9/10 per cent by weight of the dried petals, and exists in the petals as an oxonium salt (i. e., in combination with a plant acid). A yellow glucoside sap-pigment also occurs in the same flowers, but beyond the fact that it has been shown to be capable of producing an anthocyan, by reduction, and that it is not a glucoside of the flavonol myricetin, it has been further identified, on account of the small quantity present.

The rose "George Dickson" was chosen for this investigation on account of its deep red color, which would indicate a fairly large percentage of the anthocyan pigment.

One hundred grams of petals (which had been first air-dried in the shade, at room temperature, and finally over concentrated sulphuric acid), were allowed to stand in a closed vessel, with about 300 c. c. of methyl alcohol, containing 2 per cent of concentrated hydrochloric acid (to prevent pseudobase formation), for about 24 hours; the mass was then pressed, to obtain as much extract as possible, and the residue treated with a further quantity of methyl alcoholic hydrochloric acid. After standing some hours, this was filtered, with suction, and as the extraction was still incomplete, the residue was again extracted with the same solvent. The residue, after filtering and washing, possessed but a pale pink color, and further extraction was deemed unnecessary. The filtrates and washings were united; they possessed a fine, deep red color, with a bluish-violet tinge at the edge of the solution. The combined filtrates and washings were poured into about three times their volume of ether, well agitated, and allowed to stand for some hours. Practically all the anthocyan pigment separated out as a dark brown, gummy mass, from which the supernatant solution could be readily decanted.

The crude anthocyan pigment was redissolved in methyl alcoholic hydrochloric acid, and reprecipitated with ether (about two and a half times the volume of the alcoholic solution). After standing some hours, to allow precipitation to be as complete as possible, the ether-alcohol solution was decanted off and the precipitate allowed to stand for 24 hours in contact with a mixture of methyl alcohol and glacial acetic acid (to remove impurities capable of being hydrolysed or acetylated), and finally collected on a filter, washed with a small quantity of methyl alcohol (containing 1 per cent hydrochloric acid), and air-dried.

The dark brown powder thus obtained was dissolved in boiling water, an equal volume of ethyl alcohol (containing 3 per cent hydrochloric acid) added, and the solution allowed to cool; the coloring matter separated out in the form of dark brown leaflets, possessing a golden reflex. These were collected and air-dried. For identification purposes the anthocyanin chloride thus obtained was examined for the following properties: viz., crystalline form, color and reflex; color changes on the addition of ferric chloride to aqueous and alcoholic solutions; color of solutions in aqueous acid and alcohol; color changes with alkalies; behavior with Fehling’s solution (hot and cold); color of precipitate with lead acetate; and behavior with sodium bisulphate.

On comparing these properties with those given by Willstatter and Nolan for cyanin chloride, they were found to be identical: the anthocyan pigment of the red rose "George Dickson" is, therefore, the di-glucoside cyanin.—G. Currey in the Proceedings of the Royal Society for March, 1922.