HARDWICKE'S SCIENCE-GOSSIP. 



217 



THE COLOURATION OF THE ROSE, THE VIOLET, AND 



THE BUTTERCUP. 



By Dr. P. Q. KEEGAN. 



T is proposed here 

 to attempt by cer- 

 tain aDalyses to 

 discover what is 

 the precise funda- 

 mental organic 

 body which deter- 

 mines the colours 

 of the petals of 

 these three flowers. 

 Every botanical 

 student knows that 

 the blue and red 

 colours of flowers 

 are due to dis- 

 solved pigments, 

 while the yellows 

 and certain of the 

 oranges depend on 

 solid or crystalline 

 bodies combined 

 with a protoplasmic basis. In order to thoroughly 

 understand what follows, a little knowledge of organic 

 chemistry is absolutely necessary ; but I will en- 

 deavour to describe the process as briefly and as 

 clearly as possible, so that any student who may 

 happen to enjoy a lucid interval from the more severe 

 collecting (fighting) phases of his beloved science 

 may be able to follow suit. The process certainly 

 "wants a bit o' doing," but after all, it is very 

 simple, provided of course that you know how it's 

 done ! 



Having gathered some red wild-rose petals on a 

 dry day, you leave them out in the air of your study 

 for forty-eight hours or more, so that they may lose 

 some of their sugar, whereof they contain 3J per cent. 

 Now cut them up in very small pieces with a com- 

 mon pair of scissors, and place the pieces in a test- 

 tube or beaker, with some strong alcohol. Boil, 

 No. 334.— October 1892. 



pour off the liquid and filter, then boil the material 

 again with water, and pour off and filter. The two 

 liquids are mixed and evaporated down in a silver 

 or nickel basin to a small bulk, some strong solution 

 of caustic potash is added, and the whole evaporated 

 to dryness and fused, continuing the heat and stirring 

 occasionally with a glass rod until the mass is in a 

 uniform state of fusion. After cooling, the contents 

 of the basin are dissolved in hot water, and acidulated 

 with sulphuric or hydrochloric acid. After standing 

 and cooling, the liquid is filtered, and shaken up with 

 ether, which extracts and dissolves among others the 

 very substances we are in quest of. Now, what are 

 these ? They are no less than three in number, 

 and ic this particular instance are rather difficult to 

 detect, inasmuch as the amount of colouring-matter 

 in wild roses is very trifling indeed. However, if we 

 only will brush up our knowledge of organic chemis- 

 try, and have sufficient experience, we can recognise 

 here what is called protocatechuic acid, C 7 H 6 0j, 

 along with two phenols, viz., phloroglucol, C G H <; 3 , 

 and a trace of pyrogallol. But what have 

 these horrid names to do with the bewitchingly 

 beautiful tints of the queen of flowers ? I think it 

 can be shown that they have as much, and probably 

 much more, to do with them, than the man in the 

 moon has to do with the ebb and flow of the tides. 

 Not to be too stiffly scientific, I must forbear from 

 entering into details tending to prove that in the case 

 of blue, red, and some other varieties of coloured 

 flowers, it is the tannins, possibly aided by the gluco- 

 sides, which alone of all the constituents of the petals 

 can possibly be the generating cause of the bright 

 pigments thereof. Now, the aforesaid bodies which 

 we have obtained by virtue of the process just 

 described are the result of the oxidation of the 

 tannin which is proper to the rose-bush itself; and 

 precisely the same bodies can be also obtained by 

 treating the leaves or the stalks or branches of that 



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