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periment they were all nearly as bright and white as atfirst, on account, perhaps, of the mixture having melted,so as to wash and cleanse their surfaces.

4. Of the other metallic bodies, gold is the only onewhich relists the marine acid in the above way of appli-cation. As the platina in these experiments had no markof dissolution, it was presumed that this metal likewisehad resisted it; and that the deficiency in weight wasowing to some of the smaller grains having been washedoff along with the ponderous metallic matter of the vi-triol. The experiment was therefore varied, by substi-tuting, to the foregoing mixtures, mercury-sublimate, acombination of the concentrated marine acid with quick-silver; when this compound is mixed with any one of thecommon metals, gold excepted, and the mixture exposedto a proper heat, the quicksilver separates and exhales-,while the acid unites with the metal. An ounce of pla-tina was spread upon three ounces of powdered sublimatein a glass vessel, which being set in a moderate sand heat,the sublimate totally arose, leaving the platina of its ori-ginal weight, and uncorroded, though discoloured a little.

5. As the action of sublimate on bodies depends notonly on the acid being capable of corroding them, but onits having a stronger affinity to them than it has to themercury, that is, a disposition to unite with them in pre-ference to the mercury; it is possible that there may bebodies, really corrosible by the acid, but which, havingless affinity to it than mercury has, will of consequenceresist the action of sublimate. The regal cement wastherefore again had recourse to, but that none of thegrains of platina might be in danger of being lost, twicetheir weight of gold was melted with them, and themixture carefully hammered into a thin plate. A piece ofthe plate, weighing fifty grains, was surrounded with

regal