SCIENCE PAPERS, 



ON TUENSOLE. 



ALTHOUGH the subject of these remarks may by some be 

 considered more to concern the dyer than the pharmacist, I 

 trust that, taken in connection with another, substance well 

 known to chemists, and often confounded under the same name, 

 it may not prove altogether devoid of interest. 



Turnsole, or Tournesol, is a name applied to two 1 articles 

 of different origin. The one is the Litmus of English chemists 

 (Tournesol en pains of the French), a blue substance imported 

 from Holland, and believed to be derived from some species of 

 lichen. The property possessed by its solution, of being changed 

 by acids from blue to red, is its most important character. 



The other species of Turnsole, and that on which I propose Turnsole 

 to offer a few remarks, is called Turnsole Bags (Tournesol en ags ' 

 drapeaux). It is sold as pieces of very coarse hempen cloth, of 

 a purplish black colour. Steeped in water (which readily 

 extracts all the colour) we obtain a bright purple solution, 

 which is reddened on the addition of an acid or of an alkali. 

 The plant affording this colour is the Croton tinctorium, Linn. 

 Crozophora tinctoria, Endl., and la Maurelle of the French. It 

 is indigenous in the south of France, and has been cultivated 



1 The " Turnesol in linen " and " in cotton" of Pomet, being manifestly 

 different preparations, and no longer objects of commerce, are excepted. 



