123 



mineral acid : in this particular it differs materially from the 

 fuccus of Bticanum lapillus, ^^'hich as we have before re- 

 marked is unalterable. 



Its property is materially different from that of Litmus, 

 wliich is turned from blue to red with the molt trifling mix- 

 ture of any acid. It differs alfo from vegetable colours in 

 general by not being affected by alkali, whicli turns the in- 

 fufions of blue or purple flowers to green. 



The colouring matter is readily taken up by fpirit as well 

 as water, and may be ground up and formed into a pigment 

 with a fmall portion of white : and it is remarkable that the 

 colour of this fecretion is not affected by putridity, as we 

 had occafion firft to try it in a highly putrid Hate. 



Although this colour is not proof againfl: mineral acids, nor 

 fixable by any aftringents hitherto tried, either in its prima- 

 tive or acquired colour, yet it is probable fome means might 

 be found by chemical procefs to give it durability equal to 

 cochineal ; but that article has now entirely fuperceded thefe 

 more coftly dyes. 



It is remarkable that cochineal (which at firft is fimilar in 

 colour^ though not fo beautiful, "^ is determined to a bright 

 fcarlet, by a folution of tin in aqua Regia, whereas this is 

 rendered of a bluifli-green by the fame procefs. 



CiATHRATULUS. 



Q2 



