Monitoring polonium--tro in effluent and natural waters requires a method which is both rapid and sensitive. The study of radioactive disequilibrium in rocks and minerals calls for a method whiell is precise and applicable to samples of con-siderabIe chemical complexity. A survey of existing methods indicated that the most widely used technique is the spontaneous deposition of polonium on to silver from weakly acidic solutions. This method is subject to interference from oxidants, organic materials, and elements that also deposit on silver. Precipitation has usually been employed to remove these interferences as well as concentrate the 2W'o before plating. SLfAL!Ss et a2.J used calcium tannate precipitation and plated for 3 h from llydrocl~loric acid solution to obtain good recoveries from effluent samples; plating both sides of the silver disc considerably reduced sensitivity and increased the counting time. For the determination of 31OPo in biological materials, f~UNDo2 proposed a sodium hypophosphite precipitation with tellurium as a carrier. The precipitate was then dissolved and the tellurium separated from the ZlOPo by precipitation with hydrazine hydrochloride.
Plating was carried out in a special cell on to one side only of a silver disc, thus enhancing sensitivity and reducing counting time; recoveries were 80-85*/~ for plating at 80" for 90 min. To determine the ~1oPo content of zircons and uranium-rich minerals, MILLARD~ plated directly from solution without a preliminary separation. The disc was suspended in the solution with one side coated with glyptal, and yields of 93-g5ยฐ/0 were obtained after plating overnight at room temperature.
RWSI-IING~ used tin(I1) chloride to coprkcipitate SlOPo with tellurium for water analyses, and counted directly from 'the precipitate after leaving for 24 11 to allow 222Rn products to decay.
This paper describes a method for the spontaneous deposition of 2lOPo in the presence of large quantities of foreign ions. Plating is carried out by suspending a silver disc in 50 ml of hydrochloric acid solution adjusted to px 2.0 and containing 0.5 g of sodium citrate, x.0 g of hydroxylamine hydrochloride, and IO mg of bismuth hold-back carrier ; at &go", deposition is complete in I h. No preliminary separation is required and essentially quantitative recoveries are obtained from standard solutions containing as little as 0.02 pCi ElOPo. The accuracy of the method has been demonstrated by the analysis of rocks and ores of known uranium content.