The Detection of Silver in Rain Water from Cloud Seeding Experiments in Australia

Abstract

A technique is being developed for detecting silver in very low concentrations in water. It is effective down to concentrations of 5 ? 10?11 gm ml?l. The method involves collecting and concentrating the silver ions on an ion-exchange column, precipitating the silver collected as AgI and measuring its quantity by a cold-chamber method. The performance of the system has been measured using the radio-isotope Ag110 in the form of aqueous solutions of AgNO3. The column collects over 90 per cent of the silver ions from samples with concentrations greater than 10?11 gm ml?l. For column loadings down to 10?7 gram, the elution efficiency, using a strong cation (Ba++) as the eluting substance, is greater than 20 per cent. When the technique was used on samples of rainwater collected in the field, no silver was detected except when the rain fell from clouds which had been seeded with AgI.