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V. Aqua regia:

Iron:

Platina.

A saturated solution of iron in aqua regia did notsensibly act on platina: a saturated solution of platina rea-dily corroded iron, the platina precipitating. A goodquantity of yellow ochery powder settled at the bottom,and the undissolved part of the iron appeared incrustatedwith a dark coloured matter: it could not be judged fromthe colour whether the precipitation was complete, the so-lutions of platina and of iron having a great resemblancein colour.

VI. Platina:

Aqua regia and solution of iron-vitriol:

Gold.

Solution of iron in the vitriolic acid, or a solution ofthe common green vitriol of iron made in water, whichtotally precipitate gold from aqua regia, made no changein solution of platina. A mixture of platina and gold,which had been melted together and kept in fusion forsome hours, being dissolved in aqua regia, and the vitriolicsolution added, the gold was precipitated and the platinaremained dissolved. Solutions of iron in the nitrous andmarine acids did not precipitate either platina or gold.

VII. Aqua regia:

Copper:

Platina.

Platina, put into a solution of copper in aqua regia,was not sensibly acted on: plates of copper, put into solu-tion of platina, begun quickly to dissolve, and to precipi-tate the platina. The precipitate was of a dark greyish

colour*