Radiometric studies of mercury loss from fungicidal paints. II. Comparison of three phenyl mercury compounds

The fungicides, phenyl mercuric dodecyl succinate (PMS) and phenyl mercuric dimethyldithiocarbamate (PMDDC), have been prepared labelled with ²⁰³Hg. Comparative exposure tests have been carried out on emulsion paints each containing one of the labelled compounds phenyl mercuric acetate (PMA), PMS, or PMDDC. After 236 days of indoor exposure, approximate losses from films are 60 (PMA), 50 (PMS), and 20% (PMDDC). Relative losses from films of low-Hg content (0·02%) are a few per cent higher than those from comparable films of high-Hg content (0·2%). After 56 days of outdoor exposure, approximate losses are 95 (PMA), 90 (PMS), and 40% (PMDDC). PMS and PMDCC films of high-Hg content show relative losses slightly higher than those of low-Hg content; a behaviour opposite to that of PMA films. This may be due to the distribution of PMS or PMDDC through a paint film being less uniform than that of PMA. A correlation between mercury loss and rainfall is observed for all three fungicides. The loss rates from all films decrease with time during indoor exposure. Out-of-doors, this decrease becomes well defined only when a substantial portion of the fungicide has been removed by rain. The results indicate that in emulsion paint films, under the exposure conditions used in this work, PMS is retained slightly better than PMA, but that PMDDC is retained much better than either. The high retention of PMDDC is probably due to its low saturation vapour pressure and to its low solubility in water. The solubility of PMDDC in water at 20° has been determined radiometrically as 5·7 ppm.