Experiments on the Floral Colours

Abstract

IN 1837 the illustrious Berzelius wrote: “The red pigment of several kinds of berries has generally been regarded as a blue pigment reddened by an acid. This is not the case with all berries. I have examined the pigment of Prunus cerasus and of Ribes nigrum, which contain the same pigment, and this is not blue. Probably this has been surmised from tlie circumstance that the sap of these berries gives a blue precipitate with acetate of lead, but these precipitates are malate and citrate of lead, wherewith the pigment is combined.” He found that, after separating these acids from the colouring matter, the latter yields a green and not a blue precipitate with acetate of lead: and, moreover, when to its aqueous solution a little milk of lime is added sufficient to saturate all the free acid, the supernatant liquid is red and not blue, which latter it would be if its natural colour was blue. He arrives at similar conclusions with regard to the red pigment of the autumn leaves of cherry, red currant, &c.