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being imbibed by the mercury, while the platina is preci-pitated in powder, which may be separated from the amal-gam by washing.

Solution of mercury in aquafortis rendered solution ofplatina instantly turbid, and precipitated a greyish brownpowder. Solution of mercury-sublimate in water, pouredinto solution of platina, precipitated a red matter, withnumerous bright sparkling particles, the liquor continuingyellow : the precipitate bore washing with water, withoutlosing its red colour.

X. Aqua regia ;

Nickel :

Platina.

Marggraf relates, that a piece of pure regulus of co-balt, or cobald-speise, from the smalt works at Schneebergin Saxony, after being repeatedly melted with glass till allits blue-colouring matter was extracted, was readily at-tacked by solution of platina : the regulus lost its bright-ness, and became black, a yellowish powder precipitated,and the liquor looked greenish.

The substance by which the platina was here precipi-tated, and which communicated a green colour to the li-quor, I apprehend to have been the metallic body callednickel, discovered and described by Mr. Cronstedt, in theSwedish transactions for the years 1751 and 1754, one ofwhose characters is to dissolve green in aqua regia,whereasthe regulus of cobalt, strictly so called, gives a reddish so-lution. Mr. Cronstedt observes, that cobalt generally con-tains, besides its proper regulus, or the metal which givesa blue glass, a quantity both of nickel and of bismuth :that the fpeise, or metal which separates to the bottom ofthe melting-pot in making the blue glass, generally con-sists of all the three metals z the cobalt-regulus and bis-muth, which of themselves are averse to any union with

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