Permanent Colours of Opake Bodies. 207 



numerous experiments and obfervations of Dr. 

 Prieftley are the mofl confpicuous. 



From the preceding experiments and obfer- 

 vations it appears, that the colouring particles of 

 flowers and leaves, are foluble in acid, and pliio- 

 giftic, menftrua. 



The other parts of vegetables confift of mate- 

 rials, fimilar to thofe which are contained in their 

 flowers, and leaves, and undergo the fame changes, 

 from the fame caufes. I extraded from logwood, 

 its colouring particles, by repeatedly boiling it in 

 water. The wood, thus deprived of its tinging 

 matter, no longer retained its yellow colour, * but 

 was of a brown hue, fimilar to oak wood. 



I macerated fome pieces of logwood thus de- 

 prived of its colour, in aqua fortis, and, after they 

 had undergone the aflion of that acid, they were 

 wafhed in a fufficient quantity of water. The 

 wood by thefe means was reduced to ivbltenefs, 



* Moft authors, who treat of colouring fabftances, de- 

 fcribe logwood, as a red wood. I have never procured 

 logwood which was of any other colour, than jf//o<itf . It 

 imparts yellow and orange colours to diftilled water. Other 

 waters e%'trad a red tinge from it, by means of the alcali 

 ivhich they contain. Thefe obfervations are alfo appli- 

 cable to the other dying woods, to kermes, and various 

 other articles of the materia tinftcria. I fliall only add 

 that the tinftures, infufions, and folutions, which are enu- 

 merated in the preceding table of coloured liquors have 

 been dcfcribed from careful and repeated obfervations. 



By 



