USES (JF LICHENS. 



87 



a small quantity of the powdered Lichen ; if it contain any 

 of the colourless colorific principles capable of generating 

 purple dyes, the liquid will speedily assume a reddish tint, 

 which, should they be abundant, will become developed 

 into a rich purple. He may use more elegant colorific tests, 

 but we are convinced, from our own experience, that none 

 will be found so easy and so successful as the above. He 

 may make in a test-tube an alkaline or alcoholic solu- 

 tion of the Lichen, by boiling or maceration ; the addition 

 of a few drops of a solution of common bleaching powder 

 (chloride of lime) will then cause the development of a 

 fugitive red tint, if it contain any of the colorific principles 

 in question. This reaction depends on the circumstance of 

 this solution (which may be considered chemically a solution 

 of hypochlorite of lime) striking a fugitive blood-red colour 

 with any of the organic acids before mentioned. Or he may 

 macerate the Lichen in milk of lime, and precipitate by 

 hydrochloric or acetic acid its colorific principles, which he 

 can subsequently collect and weigh. By the aid of such 

 simple chemical experiments we some years ago made a 

 series of investigations, with a view to ascertain whether 

 many native and colonial Lichens could not be made avail- 

 able in dyeing, and especially as substitutes for the com- 



