4o6 Mr. Henry's Conftderations on different Materiahy 



in diftillation, reddening the blue vegetable 

 juices, but capable of uniting, with equal 

 facility, with acids, and with alkalis. That 

 though it does not revive iron, without the 

 aid of fire, yet gold and filver are precipitated, 

 by it, in their metallic form ; and that it is 

 capable of dccompofing moft metallic folutions, 

 and giving different colours to their precipitates. 



Dr. Percival had endeavoured to produce an 

 ink, by macerating iron filings, without their 

 being combined with any acid ; but, making 

 his infufion without heat, he did not fucceed. 

 The Dijon chemifts, not content with making 

 a fimilar attempt, boiled the liquor j and thus 

 obtained a violet coloured ink, the traces of 

 which were as well defined and permanent, as 

 thofe produced by ink prepared in the common 

 way, even without the addition of gum. 

 Hence it fhould feem, that the heat not only 

 enabled the aftringent principle to diffolve 

 the iron, but alfo extrafted a mucilaginous 

 matter which fupplied the ufe of gum. 



I have related thefe fajEls in order to elucidate 

 fome circumftances attending the dying of 

 black. Green vitriol was formerly ufed ; but 

 the calx of iron is too much dephlogifticated 

 in this fait, and the black produced by it is not 

 permanent. Solutions of iron in acetous acid 

 hay? pf late been preferred, efpecially for 



cotton ; 



