GENERAL INTRODUCTION
The name "radiometric analysis" is often used for the measurement of the amount of a nucleide by means of its radio-activity, but in the opinion of the present author, this term should be reserved for analytical methods in which induced or added radioactivity is applied. Of these methods isotope dilution and activation-analysis are specially important, the latter requiring a strong source of nuclear particles, the former being in fact merely a make-shift, the sensitivity of the analysis depending on an addition technique.
The term radiometric analysis is often reserved for three other types of analysis. The first (~) and most widely applied, uses the radio-active tool merely as a tracer to denote the end-point or the starting point of a reaction; as with isotope dilution the sensitivity is in principle restricted**. Both other techniques, (2) analysis with radio-active reagents and (3) analysis by exchange-reactions involving radio-active isotopes, do not suffer from this disadvantage. A survey of the literature I revealed that, notwithstanding this, both methods (2) and ( 3), but especially method (3), are less popular than method (I).
Preliminary experiments x led to the choice of (a) phosphate-seP for the quantitative paper chromatography of traces of metals --the application to lead is described below --and (b) the exchange reactions of the system: metal ion in water-metaldiethyldithiocarbamate complex in chloroform for the determination of traces of metals in solution. Applications of the latter system to lead and cobalt will be described in later papers.
QUANTITATIVE PAPER CHROMATOGRAPHY OF LEAD WITH PHOSPHATE-32P
* Publication I24a of the Research Institute for Animal Husbandry "Schoonoord". ** Method (1) is mostly carried out as a titration with a radio-active indicator and a non-radioactive reagent. It can be made more sensitive by using a radio-active reagent, but this converts method (I) to a special form of method (2). Anal. Chim. Acta, 25 (z96I) 57o--578 * Larger amounts are permitted with Whatman No. 3 mm paper. ** HUBICKI et al. xv found the solubility product of PbHPO4 to be minimal at pH 4.5. The addition of alcohol decreased the solubility. Pb3(PO,), was precipitated only above pH 6.