1818.] colouring Constituent of Roses. 299 



muriatic acid. The acid being then filtered, was evaporated, 

 with gentle heat, to dryness ; and distilled water afterwards 

 added and filtered. The surface of the clear filtered liquor was 

 now touched with a glass rod, dipped in tincture of galls ; a pale 

 whitish precipitate appeared which, upon warming the liquor, 

 became chocolate brown, and afterwards black. Some of the 

 same liquor, in a separate vessel, touched with a glass rod dipped 

 in a very diluted solution of crystallized prussiate of potass, 

 instantly exhibited an abundant blue precipitate. 



From the foregoing observations, it is plain that the petals 

 of red roses contain iron ; and, perhaps, the medical virtues 

 ascribed to the infusion of roses, if they exist at all, may be due 

 to the very inconsiderable portion of the metal present in the 

 infusion. We all know how very insignificant are the chemical 

 constituents of many chalybeate waters, destitute of which their 

 salutary properties no longer characterize them ; and also that 

 when art attempts to supply what Nature has thus sparingly 

 afforded, the same deficiency ensues. 



Afterwards I submitted other vegetable bodies to a similar 

 investigation, and found evident traces of iron, although not 

 always in equal quantity, in the petals of blue, yellow, and white 

 flowers, and in the green leaves of several plants, especially in 

 the petals and leaves of centaurea cyanus,verbascum thapsus, phlox 

 paniculata alba, alceajici folia, &c. &c. White flowers contain 

 the smallest portion of the metal ; and its exhibition is more diffi- 

 cult during their examination than in other instances. Infusions 

 made of the green leaves of the fig-tree are sometimes used, when 

 highly concentrated, to remove grease spots from black cloths 

 and stuffs. I examined an infusion of this kind made with dis- 

 tilled water, two quarts of it being reduced by boiling, in glass 

 vessels, to a pint. From this infusion, a single drop of tincture of 

 galls immediately threw down a whitish precipitate, which sepa- 

 rated and became darker by being heated ; and when collected on a 

 filterwas found to contain iron. Ammonia caused a more copious 

 precipitate of the same nature, but of a mud colour ; and this 

 also contained iron. The same results were obtained in the 

 examination of an infusion, similarly made, of ivy leaves. The 

 most remarkable results, as being, perhaps,- the most satisfac- 

 tory, were obtained from a concentrated infusion made with the 

 green leaves of the lilium tigrinum, or tiger lily. From this in- 

 fusion, a gallate of iron was instantly separated, simply by touch- 

 ing the surface in a test-tube with a glass rod dipped in tincture 

 alls, and afterwards heating the infusion to trie boiling point. 

 Ammonia, being substituted for the tincture of galls, threw down, 

 as before, a more copious precipitate containing iron. 

 I remain, Gentlemen, yours, 6cc. 



Cambridge, Sept. 15. 1818. EDWARD DANIEL CLARKE. 



