Its ſpecific gravity is 18,000^[60], when very pure. It diſſolves in aqua regia, and the loſs of phlogiſton during the ſolution, according to the experiments hitherto made may be expreſſed by 756. Beſides the muriatic acid, which when dephlogiſticated diſſolves every metal, no acid acts upon platina without it has undergone a previous calcination. It ſeems to retain its phlogiſton more obſtinately than any other metal. To melt it requires a heat greater than that at which iron melts.

I believe it has never been found quite free from iron, but this can be ſeparated by art^[61].