A total of 74 compounds were synthetized and their biological activity studied on 3888 animals and on 347 strains of various microorganisms and fungi. The drugs have a moderate toxicity. The compounds containing an ester grouping of the alkyl radical with an odd number of carbon atoms are less toxic than are those with their even number. Most toxic are drugs that carry a chlorine atom in the orthoposition of the benzene nucleus and are less so the ones containing the bromine atom in this position. The toxicity of bis-quaternary salts diminishes with the rising molecular weight of the radical, this not being found to happen in the series of monoquaternary compounds. Most drugs display a locally anesthetizing and marked antimicrobial and antifungal properties. The antimicrobial activity appears with R-CH3, gradually increasing and becoming maximal with R-C10H21.