i 5 Sl ]

A mixture os platina and iron was melted with thriceits weight of lead upon a cupel, and a strong fire kept uptill greatest part of the lead was worked off. The remain-ing mass was rugged and cavernulous: in its cavities, andat the bottom, was a very considerable quantity of a darkblackish powder with somewhat of a purplish cast, whichwas attracted, though not vigorously, by a magnetic bar.

This experiment seems decisive of the greater affinity ofplatina to lead than to iron; as it shews iron, which hadbeen previously well combined with platina, thrown outagain in its metallic form by lead. It may therefore bepresumed, that the absorption of part of the platina fromiron by lead in the first experiment, proceeded from thissuperior affinity of the platina to the lead, and not, as wasat first suspected, from its having an equal affinity to themboth.

IV. Aqua reg/a:

Zinc:

Platina.

Platina, digested in a saturated solution of zinc madein aqua regia, did not appear in the least corroded; butzinc, put into a saturated solution of platina, soon begun todissolve, and to precipitate the platina. The precipitatewas of a brownish black colour: the liquor, after the zincceased to be acted on, continued yellow, a mark that theprecipitation by zinc was not total, any more than by theunmetallic precipitants in section iii. Marggraf found,that when solution of zinc in aquafortis was mixed withsolution of platina, an orange-red or brick-coloured preci-pitate fell, the liquor continuing yellow as in the othercafe.

Tfff 2

V. Aqua,