of the resin without solubilizing the al oh 3 in the resin this permits additional amounts of al halide to be imbibed and then converted by ammonia treatment to additional amounts of al oh 3 the preferred acid halide is hcl the preferred al halide is alcl 3 the acid halide treatment of the al oh 3 containing oh resin should be done carefully taking care that the acid addition is not so rapid that a localized drop in ph to lower than about 5 is reached slow addition of acid with stirring and while monitoring the ph is recommended any convenient method for lowering the ph by addition of acid halide may be used so long as the method does not result in solubilizing a substantial amount of the al oh 3 which is already in the resin converting the al oh 3 back to al halide would be counterproductive considering that the intent is to form al oh 3 in the resin the acid halide treatment step is beneficially aided and speeded by the addition of ammonium halide especially nh 4 cl the amount of nh 4 cl added may be over a fairly broad range with about 5 25 aqueous strength of nh.