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III. Platina with the Nitrous acid.

1. Spirit of nitre diluted with water, proof aquafortis,and the strong smoking nitrous spirit, were digested sepa-rately with one third their weight of platina, in a gentleheat, for several hours. During the digestion, some smallbubbles were observed, as if a dissolution was beginning,but the liquors acquired no colour, and the sire being in-creased,. so as to keep them boiling till they had to-tally evaporated, the platina remained unchanged, exceptonly that many of the grains had become discoloured.

2. Platina was treated likewise with nitrous cements, byprocesses similar to those in which it had been exposed tothe marine fumes. An ounce of pure nitre, and an ounceand a half of green vitriol calcined to redness,were groundtogether, part of the mixture pressed smooth into a cru-cible, over which was spread an ounce of platina, and therest of the mixture above it. The crucible was coveredand luted, and the fire gradually raised, so as to make thevessel of a full red heat, in which state it was continuedfor seven or eight hours. Red nitrous fumes issued copi-ously through some small cracks which they had forced inthe luting. The crucible being grown cold, the mixturewas found not melted or baked together, but loose andpowdery. .The platina was of the same weight and appear-ance as a# first, except that many of the grains had be-come, as in the foregoing experiments, dull coloured orbrownish.

IV. Additional experiments with the foregoing acids , &c. on

platina.

Mr. Marggraf has given some experiments on thishead, which having been conducted in a somewhat diffe-rent manner from mine-, he took notice of some pheno-mena