The most commercially used pgm salts are generally their chlorides. Their main uses are: chloroplatinic acid – as a precursor for loading platinum onto substrates for heterogeneous catalysts; palladium chloride – for electronic plating; rhodium trichloride – for plating applications and catalyst loading; chloroiridic acid – for plating, especially for anode coatings for chloralkali use; osmium tetroxide – in electron microscopy; and ruthenium trichloride – for plating, especially for anode coatings for chloralkali use. J. E. Gourd