OF COBALT, &e. 425 



folublc. From tbcfe circumftanccs it may be 

 fufpcdlcd to contain plumbago. 



Into a folution of an hundred pounds, or ra- 

 ther of the folublc part of an hundred pounds 

 of mangancfe in vitriolic acid, I put a quantity 

 of zinc, which I observed to precipitate only fe- 

 ven pounds of a brown ponderous metallic pow- 

 der. This powder give* a green tinge to micro-, 

 cofmic fait, but renders borax red, and like cop- 

 per, deprives it of its tranfparency. But only a 

 very fmali part of the precipitate can be of a 

 cupreous nature ; for in its nitrous folution, un- 

 Icls the folution be very complcatly faturated, 

 the infufion offal-ammoniac fcarce produces any 

 green tinge. If, however, the volatile alkali be 

 added in L larger proportion than what is rcquifitc 

 to f.uurate the folution, a tine white powder im- 

 mediately falls, communicating as it falls a (light 

 tin^c of green to the fupernntant liquor. This 

 white powder, when colleclcd, wafhcd and dif- 

 folvcd in nitrous acid, aflumcs,upon the infufion 

 of phlogifticated alkali, in part a green, and part- 

 ly a ycllowifli colour, and fubfides to the bot- 

 tom of the veilel : whence it appears plainly to 

 be a mixture of calces of iron and zinc. 



'Ainc then docs not precipitate the manganefe 

 itfeif, but the extraneous matters accidentally 

 adhering to it, That the mangancfe remains in 

 folution together with the zinc, appears plainly 

 from what takes place on the infulion of alkali. 



For 



