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moderate cementing heat, which towards the end was in-creased to a considerable degree. On separating the pla-tina from the mixture by washing, many of its grains ap-peared divided, and its weight was somewhat increased.Being afterwards exposed hastily to a very intense fire, itdid not melt, but emitted arsenical fumes, and after thesehad ceased, the platina was found to weigh just one ounceas at first.

This experiment seeming to shew that platina and.arsenic have some disposition to unite, I was preparing toprosecute it, to see if more arsenic could: be combinedwith the platina so as to bring it into fusion, when Mr.Scheffers papers came into my hands, in which I find aremarkable experiment on this point. Mr. Marggraflikewise has since tried platina with arsenic, in a mannernot greatly different from that above mentioned.

Mr. Marggraf mixed one dram of platina with two.drams of white arsenic, and exposed the mixture to thefire in a glass retort: the arsenic rose uncoloured, and lestthe platina white and undiminished in weight. The pro-cess was repeated with the fame quantity of fresh arsenic,and the fire augmented to as great a degree as the coated,retort could bear: the arsenic still rose white, but thegrains of platina were now become black, though theystill continued malleable, and weighed as much as at first..A dram of platina, two drams of arsenic,, and one dram ofsulphur, being well mixed together and treated in the samemanner the arsenic and sulphur subliming together form-ed, as they usually do when united in these proportions,a red compound; the platina becoming blackish, andweighing two grains, or one thirtieth part, more than atfirst. It seems therefore that in this way of managingthe process, the arsenic has less effect on the platina thanin my experiment above mentioned.