1. 5,5′-Dithiobis-(2-nitrobenzoate) did not influence serum cholinesterase activity, whereas 2,2′-dithiodipyridine had an inhibitory effect. 2. The lowering of the molar extinction coefficients observed in the presence of physostigmine may be a result of a reaction between thiolate ions with carbamate moieties. 3. The use of 5,5′-dithiobis-(2-nitrobenzoate) is still recommended in investigations, especially where the quantitative aspects are significant.
