Reactive derivatives of zirconium, are provided which are in the form of a pulverulent white, non-crystallized solid which is dry in appearance, and consist of metazironic acid, ZrO (OH).sub.2, accompanied by free or weakly bound water, some of the OH.sup.- ions being optionally replaced by halide ions. The ZrO.sub.2 content of these derivatives is from 60 to 92% by weight inclusive, the water content ranges from 3 to 40%, and the halide ion content can range up to approximately 5% by weight. The solid derivatives of the invention can be easily converted into usual reactive derivatives of zirconium by reaction with an aqueous solution of an acid.