The analytical methods referred to in our heading are infected with numerous sources of error, amongst which until lately the uncertainty of our knowledge of the combining constant “Pt” played a prominent part. This uncertainty, it is true, has been removed to a great extent by Seubert's investigation “Ueber das Atomgewicht des Platins,” Liebig's Annalen (for 1881), vol. ccvii. p. 1 et seqq. The value 194·8 for Pt, which he ultimately adopted, falls in well with his analyses of the chloroplatinates of potassium and ammonium, and there can be no doubt that his chloroplatinates were close approximations to the ideal substances. Hence his atomic weight 194·8 must be admitted to be nearer the truth than the value 198 of Andrews, which, until lately, was so generally employed by chemists in the calculation of their analyses. But it does not follow that in, for instance, the determination of chloride of potassium “as metallic platinum,” the factor 2KCl : Pt = 0·7657, calculated from Seubert's Pt, gives a more correct result than even the factor 0·75252, which follows from K = 39 : Cl = 35·5, and Pt = 198.