1982 Volume 31 Issue 9 Pages T74-T79
A method for analyzing aluminum and zirconium borides is presented. Decomposition of the borides was achieved in a Uniseal Decomposition Vessel (capacity, 23 ml), in which aluminum boride was heated with (1 + 1) HNO3 at 150°C for 3 h and zirconium boride with a mixture of (1 + 1) HNO3 and (1 + 5) H2SO4 at the same temperature for 6h. Aluminum and boron in the solution obtained were separated with cation exchange resin (Dowex 50 WX 8). Boron in the effluent was determined with the titrimetric method using mannite. Aluminum adsorped on the resin was eluted with 2 M HCl and determined by chelatometric titration. Zirconium was separated from boron as zirconium hydroxide by precipitation with NaOH and by filtration with a Nuclepore membrane filter. Boron in the filtrate was determined by the above mentioned method. After dissolution of zirconium hydroxide with HCl, zirconium was precipitated with mandelic acid.The optimum concentration of HCl for the complete precipitation of zirconium mandelate was (23) M. The precipitate was filtered on a G 4 glass filter, dried at 110°C and weighted as zirconium tetramandelate. The following boride samples were analyzed: Selected. crystals of α-AlB12 and β-AlB12, and two ZrB2 samples, the one prepared by carbothermic reduction and the other by direct reaction of zirconium and boron.
