60 WRITINGS OF JAMES SMITHSON. 



If the vegetable part of this blue residuum is burned 

 away, or it is washed off with water, a portion of smalt is 

 obtained. 



On exhaling, on a water bath, a tincture of turnsol, the 

 colouring matter is left in a dry state. 



This matter heated in a platina spoon over a candle, tume- 

 fied considerably, as much as starch does, became black and 

 smoked, but did not readily inflame, nor did it burn away 

 till the blow pipe was applied. It then burned pretty 

 readily, leaving a large quantity of white saline matter. 

 This saline matter saturated by nitric acid afforded crystals 

 of nitrate of potash, and some minute crystals like hydrous 

 sulphate of lime. 



Is this potash merely that portion of this matter which 

 exists in all vegetable substances ? or is the colouring matter 

 of turnsol a compound, analogous to ulmin, of a vegetable 

 principle and potash ? Its low combustibility gives some 

 sanction to this idea. 



Of the colouring matter of the violet 



The violet is well known to be coloured by a blue matter 

 which acids change to red ; and alkalies and their carbon- 

 ates first to green and then to yellow. 



This same matter is the tinging principle of many other 

 vegetables : of some, in its blue state ; of others, made red 

 by an acid. 



If the petals of the red rose are triturated with a little 

 water and carbonate of lime, a blue liquor is obtained. Al- 

 kalis, and soluble carbonates of alkalis, render this blue 

 liquor green ; and acids restore its red colour. 



The colouring matter of the violet exists in the petals of 

 red clover, the red tips of those of the common daisy of the 

 fields, of the blue hyacinth, the holly hock, lavender, in 

 the inner leaves of the artichoke, and in numerous other 

 flowers. It likewise, made red by an acid, colours the skin 

 of several plumbs, and, I think, of the scarlet geranium, 

 and of the pomegranate tree. 



