Tannin as a reagent for zirconium

Abstract

The use of tannin in separating zirconium from other elements has been investigated. With the exception of tin and titanium almost all elements commonly associated with zirconium may be separated in a single or a double precipitation in 0.1 N to 0.15 N-hydrochloric acid solution. It is shown further that tannin gives a definite turbidity with as little as 0.002 mg of 210, per ml and quantities of 0.6 mg and over may be conveniently estimated with the reagent.Tannin was first introduced by Schoeller and Powell 1) for the separation of the acid earths, niobium and tantalum. Later Schoeller 2 ) extended its use to the preferential precipitation of zirconium. A more detailed investigation was undertaken by Schoeller and Holness '3). Recently we have modified Schoeller's method for the separation of zirconium from thorium 4 ) . T h e findings of Holness and Kear 5 ) are not quite in accordance with those of Schoetler especially as regards coprecipitation of aluminium. While Schoeller found that aluminium is coprecipitated with zirconium from 0.1 N-hydrochloric acid solution. the former authors claimed complete separation in a single precipitation from solutions just acid to methyl orange. In an attempt to reconcile the two observations however, Schoeller and Holness 3 ) surmised, in slow formation of precipitates a behaviour different from what occurred in sudden formation but no definite picture of the mechanism was put forward. While a fuller investigation of this aspect would be desirable, precipitation in two stages as employed by Schoeller and his collaborators possesses a certain disadvantage. Neutralization in the second stage of precipitation calls for extreme caution. A procedure involving definite experimental conditions offers several advantages. In this work, the behaviour of a number of common and 1) A. R.