iv] REACTIONS OF ANTHOCYANINS 57 



reactions given by various chemical reagents, i.e. sulphuric, hydro- 

 chloric and oxalic acids, ammonia, caustic potash, lime water, ferric 

 chloride, ferrous sulphate, potassium ferrocyanide, uranium, lead, 

 copper and sodium acetates, stannous chloride and others. Although 

 a certain amount of differentiation was possible on this basis of quali- 

 tative reactions, it was soon found that there were too many aberrant 

 and peculiar forms of pigment to arrive at any satisfactory classification. 



Before we close the chapter, there is yet another extract which may 

 well be quoted from the writings of Boyle (107), since it dealt two 

 hundred and fifty years ago with some of the phenomena which have 

 formed the basis of Willstatter's constitutional formulae for the cyanidin 

 of the Cornflower, i.e. the reactions of anthocyanin with acids and 

 alkalies, and its instability in water solution. 



Boyle writes : ' There is a Weed, more known to Plowmen than 

 belov'd by them, whose Flowers from their Colour are commonly call'd 

 Blew-bottles, and Corn-weed from their Growing among Corn. These 

 Flowers some Ladies do, upon the account of their Lovely Colour, think 

 worth the being Candied, which when they are, they will long retain 

 so fair a Colour, as makes them a very fine Sallad in the Winter. But 

 I have try'd, that when they are freshly gather'd, they will afford a 

 Juice, which when newly express'd, (for in some cases 'twill soon enough 

 degenerate) affords a very deep and pleasant Blew. Now, (to draw this 

 to our present Scope) by dropping on this fresh Juice, a little Spirit of 

 Salt, (that being the Acid Spirit I had then at hand) it immediately 

 turn'd (as I predicted) into a Red. And if instead of the Sowr Spirit 

 I mingled with it a little strong Solution of an Alcalizate Salt, it did 

 presently disclose a lovely Green;... And I remember, that finding 

 this Blew Liquor, when freshly made, to be capable of serving in a 

 Pen for an Ink of that Colour, I attempted by moistning one part of 

 a piece of White Paper with the Spirit of Salt I have been mentioning, 

 and another with some Alcalizate or Volatile Liquor, to draw a Line 

 on the leisurely dry'd Paper, that should, e'vn before the Ink was dry, 

 appear partly Blew, partly Red, and partly Green." 



