Alloy contains 97% Pt and 3% Ir. Melted it with zinc, dissolved zinc with HCl, remaining PM powder was treated in AR for quite long, and everything dissolved. Then denox, and drop Pt with ammonium chloride. But, Ir also goes down at the same time. I read, that there is delay for about an hour between platinum and iridium salts precipitation, and ammoniun chloroplatinate, which drops immediately, can be filtered out while iridium is still in solution. What am I doing wrong? Thanks.