Operation LAC (Large Area Coverage) was a United States Army Chemical Corps operation in 1957 and 1958 which dispersed microscopic<unk>  (ZnCdS) particles over much of the United States. The purpose was to determine the dispersion and geographic range of biological or chemical agents.<unk>  was used as it could be easily detected. It was also used in an experiment on unwitting civilians in the UK and Canada.
Zinc cadmium sulfide
Gold salts
Silver diammine fluoride
Perchloryl fluoride
Arsenic trichloride
Nickel tetracarbonyl
Silver nitrate
Pirimiphos-methyl