OF COD ALT, Ac.' 



For the alkali precipitates a powder that be* 

 comes black in the fire, tinges borax and micro- 

 cofmic fait \vith the colour peculiar to manga- 

 nefe ; which colour, however, foon fades on ac- 

 count of the 7,inc intermixed ; zinc being well 

 known to efface the colours of glafles. 



From a faturated nitrous folution of manga- 

 nefe, there is a precipitate of copper obtained by 

 the intervention of zinc ; which lias in part the 

 red colour peculiar to that metal, and partly 

 that pale green appearance which a precipitate,' 

 even a folution of fine copper ufually exhibits.- 



vi. Corollaries.. 



i. Were platina only a mixture of iron and 

 gold, thefe two metals would, of necellity, be 

 feparatcd, upon the addition of zinc to a foluti- 

 on of the mixture. Gold is precipitated from 'its 

 i'olutions by all the ether metals, and ef^echlly 

 by zinc. JUit zinc can never precipitate iron, 

 even though dillblvcd in vitriolic aciU, which in 

 other cafes combines but very ilightly with the* 

 metals. Wherefore, fmce platina is precipitated 

 by zinc, without the lols of any of its qualities, I 

 infer that iron, though often accidentally inter- 

 mixed in it, forms no ellcntial part of its fub- 

 ftancc. That which 1 ufed in my experiments 

 bad only a fourth part of iron, but the propor- 

 tion vane?; and iu common platina there K 



fonict huts 



