AbstractThe 1‐octanol/water partition coefficient (Kow) of methylmercury was determined at pH 7 in water and in aqueous solutions ranging from 0.0003 to 0.6000 M in sodium chloride. It was also determined over a pH range of 2 to 10 with a fixed sodium chloride concentration of 0.0045 M. In these experiments,Kowwas seen to increase with increasing chloride concentrations in the range 0.0 to 0.075 M and to decrease with increasing pH above 7. Results were similar whether low levels of methylmercuric chloride or methylmercuric hydroxide were used as the starting materials. Partitioning was not affected by changes in ionic strengt