0.375 g oxides were eliquibrated with 15 mL 5.0 g B/m^-3 Solution (I = 0.001-1 M NaCl), pH-setting with 1 M HCl/NaOH, Centrifugation with 7800 g for 20 min, decantates analyzed for pH and B with the azomethine-H method according to Bingham F.T. Boron. P 431-447 in: Page et al. (ed.) "Methods of soil analysis" Part 2. 2nd Ed. Agron. Monogr. 9. ASA and SSSA, Madison, WI.